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Defense against the dark arts


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Title: Defense against the dark arts

Defense against the dark arts
Section 1 Lymphatic System Anatomy
  • Lymphatic system includes cells, tissues, and
    organs responsible for defending the body
  • Environmental hazards (such as various pathogens)
  • Internal threats (such as cancer cells)
  • Lymphatics
  • Network of lymphatic vessels
  • Contains lymphocytes surrounded by lymph
    (fluid similar to interstitial fluid)
  • Also includes array of lymphoid organs and tissues

Section 1 Lymphatic System Anatomy
  • Lymphocytes (primary cells of lymphatic system)
  • Respond to
  • Invading pathogens (such as bacteria and viruses)
  • Abnormal body cells (such as virus-infected or
    cancer cells)
  • Foreign proteins (such as bacterial toxins)
  • Mostly produced in lymphoid organs and tissues
    but also in red bone marrow

Figure 19 Section 1
The components of the lymphatic system
Lymphatic Vessels and Lymph Nodes
Cervical lymph nodes
Thoracic duct
Right lymphatic duct
Lymphoid Tissues and Organs
Axillary lymph nodes
Lymphatics of mammary gland
Cisterna chyli
Lymphatics of upper limb
Mucosa-associated lymphoid tissue (MALT) in
digestive, respiratory, urinary, and
reproductive tracts
Lumbar lymph nodes
Pelvic lymph nodes
Inguinal lymph nodes
Lymphatics of lower limb
Module 19.1 Lymphatic capillaries
  • Lymphatic vessels
  • Carry lymph from peripheral tissues to venous
  • Network begins with lymphatic capillaries
    (smallest vessels)
  • Collect interstitial fluid (then called lymph)
    and transport it to larger lymphatic vessels
  • Larger vessels are similar in structure to veins
  • Have valves

Figure 19.1 1
The flow of interstitial fluid into lymphatic
capillaries, where it is called lymph
Smooth muscle
Endothelial cells
Lymphatic capillary
Blood capillaries
Loose connective tissue
Interstitial fluid
Lymph flow
Figure 19.1 3 4
Lymphatic vessel
The flow of lymph from lymphatic capillaries
to larger lymphatic vessels on the way to the
venous system
Lymphatic vessel
To larger lymphatic vessels that deliver lymph to
the venous system
Lymphatic valve
From lymphatic capillaries
Lymphatic valve
Lymphatic vessel
Valve in lymphatic vessel
LM x 65
Module 19.1 Lymphatic capillaries
  • Lymphatic capillaries
  • Present in almost every tissue, alongside
    cardiovascular capillaries
  • Differ from blood capillaries
  • Originate as pockets rather than continuous tubes
  • Have larger diameters
  • Have thinner walls
  • Basal lamina is incomplete or absent
  • Typically have a flattened or irregular outline
    in sectional view
  • Endothelial cells overlap to form one-way valves
  • Collect fluids as well as larger solutes

Figure 19.1 2
The structure of lymphatic capillaries
Incomplete or absent basal lamina
Lymph flow
Loose connective tissue
To larger lymphatics
Overlapping endothelial cells
Interstitial fluid
Interstitial fluid
Loose connective tissue
Lymphatic capillary
Blood capillary
Sectional view
Module 19.1 Review
  • a. What is the function of lymphatic vessels?
  • b. What structure prevents the backflow of lymph
    in some lymphatic vessels?
  • c. What is the function of overlapping
    endothelial cells in lymphatic capillaries?

Module 19.2 Lymphatic vessels
  • Lymphatic vessel location
  • Superficial lymphatics
  • Subcutaneous layer deep to skin
  • Areolar tissues of mucous membranes (digestive,
    respiratory, urinary, and reproductive tracts)
  • Areolar tissues of serous membranes (pleural,
    pericardial, and peritoneal cavities)
  • Deep lymphatics
  • Accommodate deep arteries and veins supplying
    skeletal muscles and other torso organs

Figure 19.2 1
Some characteristics of superficial and deep
Lymphatic Vessels
Superficial Lymphatics
Deep Lymphatics
Are located in the subcutaneous layer deep to the
skin in the areolar tissues of the mucous
membranes lining the digestive, respiratory,
urinary, and reproductive tracts and in the
areolar tissues of the serous membranes lining
the pleural, pericardial, and peritoneal cavities
Accompany deep arteries and veins supplying
skeletal muscles and other organs of the neck,
limbs, and trunk, and the walls of visceral organs
Superficial inguinal lymph nodes and lymphatic
Deep inguinal lymph nodes and lymphatic vessels
Module 19.2 Lymphatic vessels
  • Large lymphatic vessels
  • Lymphatic trunks (drain lymph from large body
  • Jugular trunks
  • Subclavian trunks
  • Bronchomediastinal trunks
  • Lumbar trunks
  • Intestinal trunk
  • Cisterna chyli
  • Expanded chamber receiving lymph from lumbar
    trunks and intestinal trunk

Module 19.2 Lymphatic vessels
  • Large lymphatic vessels (continued)
  • Lymphatic ducts (empty into subclavian veins)
  • Right lymphatic duct
  • Drains lymph from right arm, right upper torso,
    right head and neck
  • Thoracic duct
  • Drains lymph from rest of body
  • Left arm, lower limbs, lower torso, upper left
    torso, left head and neck

Figure 19.2 2
Areas of the body drained by the right
lymphatic and thoracic ducts
Drainage of thoracic duct
Drainage of right lymphatic duct
Figure 19.2 3
The relationship between the right lymphatic and
thoracic ducts and the venous system
Right internal jugular vein
Left internal jugular vein
Brachiocephalic veins
Thoracic Duct
Right Lymphatic Duct
Collects lymph from the trunks labeled below
Is formed by the merging of the trunks labeled
Left jugular trunk
Right jugular trunk
Left subclavian trunk
Right subclavian trunk
Thoracic duct entering left subclavian vein
Right lymphatic duct entering right subclavian
Left bronchomediastinal trunk
Right bronchomediastinal trunk
Superior vena cava (cut)
Rib (cut)
Thoracic duct
Azygos vein
Thoracic lymph nodes
Parietal pleura (cut)
Intestinal trunk
Interior vena cava (cut)
Cisterna chyli
Right lumbar trunk
Left lumbar trunk
Module 19.2 Lymphatic vessels
  • Lymphedema
  • Blockage of lymphatic drainage
  • Interstitial fluids accumulate and affected area
  • Most often seen in limbs
  • Can become permanent and lead to infection
  • Interstitial fluid is stagnant and pathogens

Module 19.2 Review
  • a. Name the two large lymphatic vessels into
    which the lymphatic trunks empty.
  • b. Explain lymphedema.

Module 19.3 Lymphocytes
  • Lymphocytes
  • Account for 2030 of circulating leukocytes
  • Most lymphocytes are out in lymphatic tissues
  • Three classes circulate in blood
  • T cells (80 of circulating lymphocytes)
  • Cell-mediated immunity
  • B cells (1015 of circulating lymphocytes)
  • Antibody-mediated immunity
  • NK cells (510 of circulating lymphocytes)
  • Immunological surveillance

Module 19.3 Lymphocytes
  • All lymphocytes are sensitive to specific
    chemicals (antigens)
  • Antigens can be
  • Pathogens
  • Parts or products of pathogens
  • Other foreign compounds
  • Are usually proteins but can be other common
    organic molecules as well
  • Stimulate an immune response that leads to
    destruction of target compound or organism

Module 19.3 Lymphocytes
  • Lymphocyte classes
  • T cells (three major categories)
  • Cytotoxic T cells
  • Attack foreign cells or virus-infected body cells
  • Commonly use direct contact
  • Helper T cells
  • Stimulate T cell and B cell activation and
  • Suppressor T cells
  • Inhibit T cell and B cell activation and function
  • Work with helper T cells to control immune
    response sensitivity

Module 19.3 Lymphocytes
  • Lymphocyte classes (continued)
  • B cells
  • When stimulated, become plasma cells that produce
    and secrete antibodies
  • Antibodies then circulate in body fluids to
    attack targets throughout the body

  • NK (natural killer) cells
  • Attack foreign cells, virus-infected body cells,
    and cancer cells
  • Provide continuous monitoring of peripheral

Figure 19.3 1
The three classes of lymphocytes circulating in
the bloodstream
Classes of Lymphocytes
T Cells
B Cells
NK Cells
Account for approximately 80 percent of
circulating lymphcytes are of three major types
Account for 1015 percent of circulating
Account for 510 percent of circulating
lymphocytes perform immune surveillance, attacki
ng foreign cells, body cells infected
with viruses, and cancer cells that appear
in normal tissues
Suppressor T Cells
Plasma Cells
Cytotoxic T Cells
Helper T Cells
Attack foreign cells or body cells infected by
viruses, commonly by direct contact are
the primary cells involved in the production
of cell-mediated immunity (cellular immunity)
Stimulate the activation and function of both T
cells and B cells
Inhibit the activation and function of both T
cells and B cells the interplay between
suppressor T cells and helper T cells helps
establish and control the sensitivity of
the immune response
When stimulated can differentiate into
plasma cells, which produce and secrete
antibodies are said to be responsible
for antibody-mediated immunity (humoral immunity)
because antibodies circulate widely in body fluids
Module 19.3 Lymphocytes
  • Lymphopoiesis (lymphocyte production)
  • Occurs mainly in red bone marrow
  • Lymphocyte stem cells
  • Develop from hemocytoblasts
  • Produce all lymphocyte types from two groups
  • Group migrates to thymus
  • Isolated by bloodthymus barrier
  • Become T cells and reenter bloodstream
  • Group remains in bone to finish development
  • Become B cells and NK cells
  • Mature T cells and B cells can reproduce

Module 19.3 Review
  • a. Identify the three main classes of
  • b. Which cells are responsible for
    antibody-mediated immunity?
  • c . What tissues are involved in lymphopoiesis?

Module 19.4 Lymphatic tissues and organs
  • Lymphatic tissues
  • Connective tissues dominated by lymphocytes
  • May form aggregations of lymphocytes (lymphoid
  • Examples
  • Aggregated lymphoid nodules (Peyer patches)
  • Deep to epithelium in small intestine
  • Mucosa-associated lymphoid tissue (MALT)
  • Protect epithelia of digestive, respiratory,
    urinary, and reproductive tracts

Figure 19.4 1
A photomicrograph and a drawing of aggregated
lymphoid nodules in the intestinal mucosa
An aggregated lymphoid nodule in the intestinal
Intestinal lumen
Mucous membrane of intestinal wall
Germinal center
Aggregated lymphoid nodule in intestinal mucosa
Underlying connective tissue
Aggregated lymphoid nodules
LM x 20
Module 19.4 Lymphatic tissues and organs
  • Tonsils
  • Lymphoid nodules in pharynx wall
  • Inflammation of tonsils tonsillitis
  • Palatine (posterior, inferior margin of oral
  • Paired
  • Pharyngeal (posterior, superior wall of pharynx)
  • Often called adenoid
  • Single
  • Lingual (deep to epithelium at base of tongue)
  • Paired

Figure 19.4 2
The location and histology of tonsils
Germinal centers within nodules
Pharyngeal epithelium
The location of the tonsils
LM x 40
Pharyngeal tonsil
Pharyngeal tonsil
Hard palate
Palatine tonsil
Lingual tonsil
Module 19.4 Lymphatic tissues and organs
  • Lymph nodes
  • Small lymphoid organs surrounded by fibrous
    connective tissue capsule
  • Diameter range 125 mm (about 1 in.)
  • Large lymph nodes (lymph glands) located in neck,
    groin, axillae
  • Function as filters, removing 99 of pathogens
    from lymph before fluid returns to bloodstream

Module 19.4 Lymphatic tissues and organs
  • Pathway through lymph node
  • Afferent lymphatics (afferens, to bring to) bring
    lymph to node on opposite side from hilum
  • ? Subcapsular space
  • Macrophages and dendritic cells (immune response)
  • ? Outer cortex
  • B cells in germinal centers
  • ? Deep cortex
  • T cells
  • ? Medullary sinus
  • B cells and plasma cells
  • ? Exit node through efferent (efferens, to bring
    out) lymphatics

Figure 19.4 3
Lymph node
Lymph vessel
Lymph nodes
The functional anatomy of lymph nodes
Path of Lymph Flow through a Lymph Node
Efferent lymphatics (efferens, to bring
out) leave the lymph node at the hilum.
These vessels collect lymph from the medullary
sinus and carry it toward the venous circulation.
Lymph node artery and vein
Lymph continues into the medullary sinus at the
core of the lymph node. This region contains B
cells and plasma cells.
Lymph then flows through lymph sinuses in
the deep cortex, which is dominated by T cells.
Lymph next flows into the outer cortex,
which contains B cells within germinal centers
that resemble those of lymphoid nodules.
The afferent vessels deliver lymph to
the subcapsular space, a meshwork of
reticular fibers, macrophages, and dendritic
cells. Dendritic cells are involved in the
initiation of the immune response.
Germinal center
Afferent lymphatics (afferens, to bring to) carry
lymph to the lymph node from peripheral tissues.
The afferent lymphatics penetrate the capsule of
the lymph node on the side opposite the hilum.
Module 19.4 Review
  • a. Define tonsil.
  • b. Name the lymphoid tissue that protects
    epithelia lining the digestive, respiratory,
    urinary, and reproductive tracts.

Module 19.5 Thymus
  • Function of the thymus and age-related effects
  • Produces several hormones (thymosins) important
    in functional T cell development
  • More important in children
  • Size is largest (40 g) before puberty
  • Diminishes in size and becomes fibrous
  • After age 50, size can be lt12 g and secretions
  • May lead to increased susceptibility to disease

Module 19.5 Thymus
  • Structure of the thymus
  • Bilobed gland in mediastinum, posterior to
  • Left and right lobes with smaller partitions
    (septa) dividing it into lobules
  • Each lobule contains
  • Cortex (reticular epithelial cells and
  • Has bloodthymus barrier to isolate developing
    T cells
  • Medulla (reticular epithelial cells and
    lymphocytes organized into thymic corpuscles)
  • Developed T cells enter bloodstream (no barrier)

Figure 19.5 2
The surface anatomy of the thymus
Left lobe
Right lobe
Figure 19.5 3 4
The histology of the thymus
LM x 50
Thymus gland
Thymic corpuscle
Reticular epithelial cells
LM x 532
Thymic corpuscle
Module 19.5 Review
  • a. Where is the thymus located?
  • b. Which cells constitute and maintain the
    bloodthymus barrier?
  • c. Describe the gross anatomy of the thymus.

Module 19.6 Spleen
  • Similar to a lymph node filters blood for the
    body to prevent pathogens from reaching vital
  • Extremely delicate tissue
  • If damaged or ruptured it is to difficult to fix
    surgically and a slenectomy is usually done

Figure 19.6 1
A transverse section of the trunk showing the
location of the spleen within the abdominopelvic
Gastrosplenic ligament
Gastric area
Diaphragmatic surface of the spleen
Renal area
Module 19.6 Spleen
  • Internal functional anatomy
  • Outer capsule of collagen and elastic fibers
  • Protects but overall spleen structure is delicate
  • Damage can necessitate removal (splenectomy)
  • Trabeculae
  • Fibrous partitions that allow room for blood
  • Pulp (cellular components allowing identification
    and removal of damaged or infected cells in
  • Red pulp (large quantities of RBCs)
  • White pulp (resemble lymphoid nodules with
    lymphocytes, macrophages, and dendritic cells)

Figure 19.6 4
Fibrous partitions within which blood vessels
Red pulp
Trabecular artery
White pulp of splenic nodule
Central artery in splenic nodule
The histological appearance of the spleen
LM x 50
Figure 19.6 5
Module 19.6 Review
  • a. What is the function of the spleen?
  • b. Describe red pulp and white pulp found in the
  • .

Section 2 Nonspecific Defenses
  • Two complementary mechanisms work to fight
    infection, illness, and disease
  • Specific defenses (protect against particular
  • Depend on specific lymphocyte activities
  • Produce state of protection (immunity or specific

Section 2 Nonspecific Defenses
  • Two complementary mechanisms work to fight
    infection, illness, and disease (continued)
  • Nonspecific defenses (present from birth and do
    not distinguish one type of threat from another)
  • Physical barriers
  • Phagocytes
  • Immunological surveillance
  • Interferons
  • Complement
  • Inflammatory response
  • Fever

Animation Immunity Nonspecific Defenses
Module 19.7 Physical barriers and phagocytes
  • Physical barriers
  • Integumentary system
  • Secretions from sebaceous and sweat glands wash
    away microorganisms and chemical agents
  • May also contain bactericidal chemicals,
    destructive enzymes (lysozymes), and antibodies
  • Hair provides protection from mechanical abrasion
    and prevents hazardous materials or insects from
    contacting skin
  • Multiple layers of epithelial cells with keratin
    that are connected with desmosomes

Figure 19.7 1
Duct of eccrine sweat gland
Structures in the skin that constitute a physical
Keratinized cells
Sebaceous gland
Most epithelia are protected by specialized
accessory structures and secretions. The
epidermal surface also receives the secretions
of sebaceous and sweat glands. These secretions,
which flush the surface to wash away
microorganisms and chemical agents, may also
contain bactericidal chemicals,
destructive enzymes (lysozymes), and antibodies.
The hairs on most areas of your bodys surface
provide some protection against
mechanical abrasion (especially on the
scalp), and they often prevent hazardous materials
or insects from contacting your skin.
The epithelial covering of the skin has multiple
layers, a coating of keratinized cells, and a
network of desmosomes that lock adjacent cells
Module 19.7 Physical barriers and phagocytes
  • Physical barriers (continued)
  • Other epithelial linings
  • Found along digestive, respiratory, urinary, and
    reproductive tracts
  • Cells provide physical barrier
  • Secretions (mucus, enzymes, stomach acid) often
    ensnare, destroy, or wash away pathogenic material

Figure 19.7 2
The barrier provided by the epithelia lining the
digestive, respiratory, urinary, and reproductive
Tight junctions
Mucus coating
Secretory cell
Basal lamina
Mucus bathes most surfaces of your digestive
tract, and your stomach contains a powerful acid
that can destroy many pathogens. Mucus moves
across the lining of the respiratory tract, urine
flushes the urinary passageways, and
glandular secretions do the same for
the reproductive tract. Special
enzymes, antibodies, and an acidic pH add to the
effectiveness of these secretions.
Epithelial cells tied together by tight junctions
and supported by a fibrous basal lamina
Module 19.7 Physical barriers and phagocytes
  • Phagocytes
  • Engulf and destroy foreign compounds and
  • First line of cellular defense against
    pathogenic invasion
  • Types
  • Neutrophils (in bloodstream and tissues)
  • Phagocytize cellular debris or bacteria
  • Eosinophils (less abundant)
  • Phagocytize foreign compounds and antibody-coated
  • Macrophages (derived from monocytes)
  • Fixed (permanent residents of certain organs)
  • Free (travel throughout body)

Figure 19.7 3
Types of Phagocytes
There are two major classes of macrophages
derived from the monocytes of the circulating
blood. This collection of phagocytic cells is
called the monocytemacrophage system, or
the reticuloendothelial system.
12 µm
810 µm
Neutrophils are abundant, mobile, and quick
to phagocytize cellular debris or
invading bacteria. They circulate in
the bloodstream and roam through peripheral
tissues, especially at sites of injury
or infection.
Eosinophils, which are less abundant than
neutrophils, phagocytize foreign componds
or pathogens that have been coated
with antibodies.
Free macrophages travel throughout the body,
arriving at the site of an injury by migrating
through adjacent tissues or by recruitment from
the circulating blood.
Fixed macrophages are permanent residents of
specific tissues and organs and are scattered
among connective tissues. They normally do not
move within these tissues.
Figure 19.7 4
Module 19.7 Review
  • a. Define chemotaxis.
  • b. How does the integumentary system protect the
  • c. Identify the types of phagocytes in the body,
    and differentiate between fixed macrophages and
    free macrophages.

Module 19.8 Immunological surveillance
  • Immunological surveillance
  • Constant monitoring of normal tissues by NK cells
  • Normal cells are generally ignored by immune
  • Cancer cells often contain tumor-specific
  • NK cells recognize as abnormal and destroy
  • NK cells recognize bacteria, foreign cells,
    virus-infected cells, and cancer cells

Module 19.8 Immunological surveillance
  • Steps of NK recognition and destruction
  • Presence of unusual plasma membrane activates NK
  • NK cell adheres to target cell
  • Golgi apparatus moves within NK cell near target
  • Produces many secretory vesicles containing
  • Perforins release from NK cell and arrive at
    target cell
  • Perforins create pores in target cell membrane
  • Target cell can no longer maintain its internal
    environment and disintegrates

Figure 19.8 1
The steps by which NK cells recognize and kill
target cells
Step 1 If a cell has unusual components in
its plasma membrane, an NK cell recognizes that
other cell as abnormal. Such recognition
activates the NK cell, which then adheres to its
target cell.
Step 2 The Golgi apparatus moves around the
nucleus until the maturing face points
directly toward the abnormal cell. A flood of
secretory vesicles is then produced at the Golgi
apparatus. These vesicles, which contain proteins
called perforins, travel through the cytoplasm
toward the cell surface.
Step 3 The perforins are released at the
cell surface by exocytosis and diffuse across
the narrow gap separating the NK cell from
its target.
Step 4 As a result of the pores made of
perforin molecules, the target cell can no longer
maintain its internal environment, and it
quickly disintegrates.
Golgi apparatus
NK cell
Abnormal cell
Perforin molecules
Pores produced by the interaction of
perforin molecules
Abnormal cell
NK cell
Module 19.8 Immunological surveillance
  • NK cells also destroy abnormal cells
  • Abnormal daughter cells occur during cell
  • Some abnormal cells become cancer cells

Figure 19.8 2
The process whereby NK cells detect and destroy
abnormal cells resulting from faulty cell division
NK cell identifies and destroys abnormal cell
Abnormal cell
Stem cell
Daughter cells
Daughter cells
Module 19.8 Immunological surveillance
  • Immunological escape
  • Immunological surveillance by NK cells is not
  • Primary tumors may be surrounded by a capsule and
    escape detection
  • Released malignant cells may be detected and
  • Daughter tumor cells sometimes do not display
    tumor-specific antigens or secrete chemicals that
    kill NK cells
  • Cancer cells can spread and create secondary

Figure 19.8 3
The process of immunological escape
NK cell
Once immunological escape has occurred, cancer
cells can multiply and spread without
interference by NK cells. They can then move
throughout the body, establishing potentially
lethal secondary tumors.
As malignant tumor cells begin migrating into
surrounding tissues, they can be detected
and destroyed by NK cells.
Sometimes a daughter cell will be produced that
either does not display tumor-specific antigens,
or that secretes chemicals that destroy NK cells.
Such a cell will survive and be free to grow
and divide.
The cells within a primary tumor may grow
rapidly, and if the tumor has a surrounding
capsule, the cells within may not provoke a
massive response by NK cells.
Module 19.8 Review
  • a. Define immunological surveillance.
  • b. How do NK cells detect cancer cells?
  • c. If NK cells are engaged in immunological
    surveillance, how do cancer cells spread?

Module 19.9 Interferons and the complement system
  • Interferons
  • Small proteins released by activated lymphocytes,
    macrophages, and virus-infected tissues
  • Trigger antiviral proteins in cytoplasm of nearby
  • Do not prevent entry of viruses but interfere
    with viral replication
  • Also stimulate activities of macrophages and NK

Module 19.9 Interferons and the complement system
  • Interferons (continued)
  • Three types
  • Alpha (a) interferons (produced by virus-infected
  • Attract and stimulate NK cells and give viral
  • Beta (ß) interferons (secreted by fibroblasts)
  • Slow inflammation in damaged area
  • Gamma (?) interferons (secreted by T cells and NK
  • Stimulate macrophage activity

Figure 19.9 1
Three of the types of interferons
Alpha (a)-interferons are produced by
cells infected with viruses. They attract and
stimulate NK cells and enhance resistance to
viral infection.
Beta (ß)-interferons, secreted by
fibroblasts, slow inflammation in a damaged area.
Gamma (?)-interferons, secreted by T cells and NK
cells, stimulate macrophage activity.
Module 19.9 Interferons and the complement system
  • Complement system (complements antibody action)
  • 11 plasma proteins that interact to attach to
    foreign cells
  • Two pathways of activation
  • Classical pathway (most rapid and effective)
  • Complement proteins attach to antibody already
    bound to pathogen
  • Attached protein activates and initiates cascade
    to activate and attach other complement proteins
  • Alternative pathway
  • Several complement proteins (notably properdin)
    activate in plasma after contacting foreign

Module 19.9 Interferons and the complement system
  • Complement system effects
  • Pore formation (formed by many complement
  • Destroys integrity of target cell
  • Enhanced phagocytosis
  • Attracts phagocytes and makes target cells easier
    to engulf
  • Opsonization
  • Histamine release
  • By mast cells and basophils
  • Increases inflammation and blood flow to region

Animation Immunity Complement
Module 19.9 Review
  • a. Define interferons.
  • b. Briefly explain the role of complement
  • c. What is the effect of histamine released by
    complement system activation?

Module 19.10 Inflammation and fever
  • Inflammatory response
  • Localized tissue response that produces
  • Local swelling
  • Redness
  • Heat
  • Pain
  • Complex process of inflammation can be triggered
  • Cells that are damaged from any source release
    prostaglandins, proteins, and potassium ions
  • Foreign proteins or pathogens

Module 19.10 Inflammation and fever
  • The events in inflammation
  • Tissue damage causes chemical change in
    interstitial fluid
  • Mast cell activation
  • Release of histamine and heparin
  • Causes
  • Increased blood flow to area
  • Clot formation
  • Phagocyte attraction (removes debris and
    activates specific defenses)
  • Tissue repair
  • Pathogen removal, clot erosion, scar tissue

Module 19.10 Inflammation and fever
  • Fever
  • Maintenance of body temperature gt37.2C (99F)
  • Pyrogens (pyro-, fever or heat, -gen,
  • Reset temperature thermostat in hypothalamus
  • Raises body temperature
  • Functions
  • May inhibit some viruses and bacteria
  • Increases metabolic rate which may accelerate
    tissue defenses and repair process

Figure 19.10 3
A summary of the bodys nonspecific defenses
Physical Barriers
Prevent approach of and deny access to pathogens
Duct of eccrine sweat gland
Remove debris and pathogens
Fixed macrophage
Free macrophage
Immunological Surveillance
Destroys abnormal cells
Lysed abnormal cell
Natural killer cell
Increase resistance of cells to viral
infection slow the spread of disease
Interferons released by activated lymphocytes,
macrophages, or virus-infected cells
Figure 19.10 3
A summary of the bodys nonspecific defenses
Complement System
Attacks and breaks down the surfaces of cells,
bacteria, and viruses attracts
phagocytes stimulates inflammation
Lysed pathogen
Inflammatory Response
Blood flow increased Phagocytes activated
Damaged area isolated by clotting reaction
Capillary permeability increased Complement
activated Regional temperature increased
Specific defenses activated
Multiple effects
Mast cell
Mobilizes defenses accelerates repairs inhibits
Body temperature rises above 37.2C in response
to pyrogens
Module 19.10 Review
  • a. List the bodys nonspecific defenses.
  • b. A rise in the level of interferons in the
    body suggests what kind of infection?
  • c. What effects do pyrogens have in the body?

Section 3 Specific Defenses
  • Specific defenses
  • Coordinated activities of T cells and B cells
  • Produce immunity
  • Specific resistance against potentially dangerous
  • T cells (cell-mediated immunity)
  • Defend against abnormal cells and pathogens
    inside cells
  • B cells (antibody-mediated immunity)
  • Defend against antigens and pathogens in body

Figure 19 Section 3 1
The various forms of immunity
Specific Defenses (Immunity)
Respond to threats on an individualized basis
Aquired Immunity
Innate Immunity
Is not present at birth is acquired against a
specific antigen only upon exposure to that
antigen or receipt of antibodies from some other
Genetically determinedno prior exposure or
antibody production involved
Active Immunity (Immune Response)
Passive Immunity
Develops in response to antigen exposure
Produced by transfer of antibodies from another
Naturally acquired passive immunity
Artificially acquired passive immunity
Naturally acquired active immunity
Artificially acquired active immunity
Develops after administration of an
antigen (usually through vaccination).
These activities stimulate an immune response
and promote immunity to that particular antigen.
Conferred by transfer of maternal antibodies
across placenta or in breast milk
Conferred by administration of antibodies
to combat infection
Develops after exposure to antigens in environment
Section 3 Specific Defenses
  • Properties of immunity
  • Specificity
  • T cells and B cells bind only one antigen
  • Versatility
  • Millions of lymphocytes, each sensitive to a
    different antigen
  • Immunologic memory
  • Memory cells remember antigens for future
  • Tolerance
  • Ignoring normal self tissues

Module 19.11 Triggering an immune response
  • Phagocytes activated by antigen exposure
    stimulate specific immune responses
  • To trigger a response, antigens or antigenic
    fragments must appear in plasma membranes from
  • Infecting cells or being processed by
  • Antigen presentation

Figure 19.11 1
Direct Physical and Chemical Attack
Cell-Mediated Immunity
An overview of the immune response
Activated T cells find the pathogens and attack
them through phagocytosis or the release of
chemical toxins.
Antigens or Antigenic Fragments in Body Fluids
Specific Defenses
Antigen presentation triggers specific defenses,
or an immune response.
Most antigens must either infect cells or
be processed by phagocytes before
specific defenses are activated. The trigger is
the appearance of antigens of antigenic fragments
in plasma membranes this is called
antigen presentation.
T cells activated
Phagocytes activated
Destruction of antigens
Communication and feedback
Antibody-Mediated Immunity
Attack by Circulating Antibodies
Activated B cells give rise to cells that
produce antibodies.
Module 19.11 Triggering an immune response
  • Major histocompatibility complex (MHC) proteins
  • Genetically determined membrane glycoproteins
    present on all cells
  • Synthesis controlled by portion of chromosome 6
  • Major histocompatibility complex
  • Foreign antigens are attached to newly
    synthesized MHC proteins and appear on cell
  • T cells bind antigen-MHC complex and become

Module 19.11 Triggering an immune response
  • MHC proteins
  • Two classes
  • Class I MHC proteins
  • Present on all cells
  • Create complex when cell is infected with
    bacteria or viruses
  • Class II MHC proteins
  • Only in membranes of antigen-presenting cells
  • Examples monocytemacrophages, dendritic cells
  • Create complex with phagocytized pathogens

Figure 19.11 2
The events of antigen presentation in an infected
body cell
Plasma membrane
The abnormal peptides are displayed by Class I
MHC proteins on the plasma membrane.
Antigen presentation by Class I MHC proteins is
triggered by viral or bacterial infection of a
body cell.
Viral or bacterial pathogen
Transport vesicle
The infection results in the appearance
of abnormal peptides in the cytoplasm.
After export to the Golgi apparatus, the MHC
proteins reach the plasma membrane
within transport vesicles.
The abnormal peptides are incorporated into Class
I MHC proteins as they are synthesized at
the endoplasmic reticulum.
Endoplasmic reticulum
Figure 19.11 3
The events of antigen presentation in a
phagocytic cell
Plasma membrane
Antigenic fragments are displayed by Class II MHC
proteins on the plasma membrane.
Phagocytic APCs engulf the extracellular pathogens
Antigenic fragments are bound to Class II MHC
Lysosomal action produces antigenic fragments.
The endoplasmic reticulum produces Class II MHC
Endoplasmic reticulum
Phagocytic cell
Module 19.11 Review
  • a. Describe antigen presentation.
  • b. What is the major histocompatibility complex
  • c. Where are Class I MHC proteins and Class II
    MHC proteins found?

Module 19.12 T cell activation by infected cells
  • Inactive T cells must bind the specific
    MHC-antigen complex that the T cell is programmed
    to detect
  • Antigen recognition
  • Two classes of T cell CD (cluster of
    differentiation) markers can recognize antigens
  • CD8 markers (on CD8 T cells)
  • Respond to Class I MHC proteins
  • CD4 markers (on CD4 T cells)
  • Respond to Class II MHC proteins

Figure 19.12 1
The structures involved in the process of antigen
Inactive T cell
Antigen recognition protein
MHC protein
Infected body cell (including APCs)
Figure 19.12 2
CD (cluster of differentiation) markers, the
membrane proteins involved in antigen recognition
CD Markers
There are at least 70 different CD markers, but
only two associated with T cells are important to
our discussion.
CD4 Markers
CD8 Markers
CD8 markers are found on CD8 T cells. CD8 T cells
respond to antigens presented by Class I MHC
CD4 markers are found on CD4 T cells. CD4 T
cells, discussed further in the next module,
respond to antigens presented by Class II MHC
Module 19.12 T cell activation by infected cells
  • Steps of CD8 T cell activation
  • Antigen recognition
  • Costimulation
  • Physical or chemical stimulation of T cell in
    addition to the Class I MHC molecule
  • T cell activation and cell division
  • Three CD8 T cells produced
  • Cytotoxic T cells (TC cells)
  • Memory TC cells
  • Suppressor T cells (TS cells)

Figure 19.12 3 4
Events in the stimulation and formation of
cytotoxic, memory TC, and suppressor T cells
Cytotoxic T Cells Seek Out Antigen-Bearing Cells
Cytotoxic T cells, also called TC cells, seek out
and destroy abnormal and infected cells.
Cytotoxic T cells are highly mobile cells that
roam throughout injured tissues. When a TC cell
encounters its target antigens bound to Class I
MHC proteins, it attacks the target cell.
Destruction of Target Cells
Activation and Cell Division
Antigen Recognition
The TC cell destroys the antigen- bearing cell.
It may use several different mechanisms to kill
the target cell.
Antigen recognition occurs when a CD8 T cell
encounters an appropriate antigen on the surface
of another cell, bound to a Class I MHC protein.
Antigen recognition results in T cell activation
and cell division, producing three different
types of CD8 T cells.
Viral or bacterial antigen
Inactive CD8 T cell
Infected cell
Memory TC Cells Are Produced
Memory TC cells are produced by the same cell
divisions that produce cytotoxic T cells.
Thousands of these cells are produced, but they
do not differentiate further the first time
the antigen triggers an immune response.
Destruction of target cell membrane through
the release of perforins
Memory TC cells (inactive)
Activation of genes within the target cell
nucleus that results in the self-destruction of
the cell through a process called apoptosis
Suppressor T Cells Provide a Delayed Suppression
Costimulation activates CD8 T cell
Suppressor T cells (TS cells) suppress the
responses of other T cells and B cells by
secreting suppression factors that limit
the degree of immune system activation. Suppressio
n does not occur immediately, because suppressor
T cell activation takes much longer than the
activation of other types of T cells, and so
suppressor T cells act only after the initial
immune response.
Disruption of cell metabolism through the release
of lymphotoxin (lim-fo-TOK-sin)
Class I MHC
T cell receptor
Suppressor T cells
CD8 T cell
Infected cell
Before activation can occur, a T cell must be
chemically or physically stimulated by the
abnormal target cell. This vital secondary
binding process, called costimulation, confirms
the activation signal. Costimulation is like the
safety on a gun It helps prevent T cells
from mistakenly attacking normal (self) tissues.
Module 19.12 T cell activation by infected cells
  • CD8 T cell types
  • Cytotoxic TC cells
  • Seek out and destroy abnormal and infected cells
    in injured tissues
  • Target cells must have specific Class I MHC
  • Destructive mechanisms
  • Release of perforins
  • Activate target cell self-destruction genes for
    cell death (apoptosis)
  • Disruption of cell metabolism with lymphotoxin

Module 19.12 T cell activation by infected cells
  • CD8 T cell types (continued)
  • Memory TC cells
  • Produced but do not differentiate further during
    first antigen exposure
  • Upon 2nd exposure to same antigen, memory TC
    cells become cytotoxic T cells
  • Suppressor T cells
  • Secrete suppression factors to limit responses of
    other T cells and B cells
  • Also act only after first antigen exposure
    (initial immune response)

Module 19.12 Review
  • a. Identify the three major types of T cells
    activated by Class I MHC proteins.
  • b. Describe CD markers.
  • c. How can the presence of an abnormal antigen
    in the cytoplasm of a cell initiate an immune

Module 19.13 CD4 T cell and B cell activation
  • B cell activation
  • Must bind specific antigen
  • Antigens are brought into cell through
    endocytosis and then placed on surface of cell
    bound to Class II MHC proteins
  • Sensitization
  • Full activation occurs when activated helper T
    cell binds to sensitized B cell antigen-Class II
    MHC complex
  • Activated B cells produce
  • Memory B cells (inactive until 2nd exposure to
  • Plasma cells (activated B cells that produce

Module 19.13 CD4 T cell and B cell activation
Animation B Cell Sensitization
Figure 19.13
The process whereby stimulation of CD4 T cells
results in the production of antibodies
Antigen Recognition by CD4 T Cell
B Cell Sensitization
B Cell Activation
Division, Differentiation, and Antibody Production
Memory B cells remain in reserve to deal with
subsequent injuries of infections that involve
the same antigens. On subsequent exposure,
the memory B cells respond by differentiating
into plasma cells that secrete antibodies
in massive quantities.
Class II MHC
Sensitized B cell
Foreign antigen
Antigen-presenting cell (APC)
Class II MHC
Costimulation by cytokines
Class II MHC
T cell receptor
Memory B cells (inactive)
Sensitized B cell
Inactive B cell
Antigens bound to antibody molecules
Helper T cell
Inactive CD4 (TH) cell
Activated B cell
CD4 protein
Sensitized B cell
Cell division
T cell receptor
TH cell
The Golgi apparatus is packaging
membrane receptors (red) that will
be incorporated into the surface of the cell.
These receptors are essential to
the costimulation of B cells.
Active B cells
CD4 T Cell Activation and Cell Division
Stimulation by cytokines
Active helper T cell
Under stimulation by cytokines from helper T
cells, clones of active B cells
differentiate into plasma cells, each capable
of secreting up to 100 million antibody molecules
each hour.
Active helper T cell
Plasma cells
Memory TH cells (inactive)
Active helper T cells
Active helper T cells secrete cytokines that
stimulate both cell-mediated and antibody-mediated
Antibody molecules
An activated helper T cell
Fluorescent LM x 400
Module 19.13 Review
  • a. Define sensitization.
  • b. Explain the function of cytokines secreted by
    helper T cells.
  • c. If you observed a higher-than-normal number
    of plasma cells in a sample of lymph, would you
    expect antibody levels in the blood to be higher
    or lower than normal?

Module 19.14 Antibodies
  • Antibody molecules
  • Consist of two parallel polypeptide chains
  • One pair of heavy chains
  • One pair of light chains
  • Each pair contains
  • Constant segments
  • On heavy chains, form the base of antibody
  • Variable segments
  • Free tips are antigen binding sites
  • Differences in amino acid sequences produce
    variability needed for different antibodies

Figure 19.14 1
The structure of an antibody molecule
Antigen binding sites
Heavy chain
Antigen binding site
Disulfide bond
Variable segment
Light chain
Binding sites that can activate the complement
system are covered when the antibody is secreted
but become exposed when the antibody binds to an
Constant segments of light and heavy chains
Binding sites may also be present that attach
the secreted antibody to the surfaces of
macrophages, basophils, or mast cells.
Module 19.14 Antibodies
  • Antigen-antibody complex
  • When a specific antibody binds to corresponding
    antigenic determinant sites (binding sites) on
  • Complete antigens
  • Have at least two antigenic determinant sites,
    one for each binding site on antibody