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Immunology: Basic Principles of Adaptive Immunity and Immunizations

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Title: Immunology: Basic Principles of Adaptive Immunity and Immunizations


1
Immunology Basic Principles of Adaptive Immunity
and Immunizations
  • 2007

2
Adaptive Immunity
  • Recognize non self
  • Respond to a foreign invader
  • Distinguish between invaders( potential pathogen)

3
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4
Antigen
  • Is a substance( molecule) that the body
    identifies as foreign and it mounts an immune
    response.
  • It is also known as an immunogen
  • Most antigens are proteins
  • Some are glycoproteins, nucleoproteins, or
    polysaccharides

5
Proteins as antigens
  • Proteins are generally more immunogenic
  • Their structure is more complex
  • Large proteins may have several epitopes or
    antigenic determinants

6
Hepatitis antigens
  • Hepatitis surface antigen is a molecule attached
    to the exterior or the virus
  • Evokes an immune response
  • First antigen detectable

7
Haptens
  • Haptens are smaller molecules that can be
    antigenic if they bind to a larger molecule
  • The antigen is the result of the combination.
    Neither is antigenic by itself

8
Antibody
  • Antibodies are molecules that are produced as a
    response to foreign invaders
  • It is specific for an antigen
  • It has the capacity to bind to the antigen

9
Titer
  • Titers are the quantitiy of an antigen required
    to evoke an immune response
  • It is quantifiable
  • Measured in clinical situations to determine
    immunity,the presence of disease,the course of an
    infection

10
Antibody titer( definition and importance)
  • Quantity to bind to and neutralize a particular
    quantity of an antigen
  • Rubella is a virus that produces teratogenic
    effects in a fetus
  • Rubella titers are diagnostically significant in
    young women planning on pregnancy

11
Effector Response
  • Recognition of a non self presence causes a
    series of response reactions
  • Divided into
  • a. Humoral response Based upon the presence to
    antibodies
  • b.Cellular response based upon the activity of
    special cells such as T lymphocytes

12
Development of the immune system( Immune cells)
  • Differentiation of stem cells into lymphocytes is
    influenced by other tissues
  • B cells are differentiated in the bone marrow
  • Found in the lymph nodes, spleen, gut associated
    lymphoid tissues( GALT)
  • B CELLS
  • T cells are are differentiated in the thymus
  • They are located in lymph nodes
  • They are the majority of circulating lymphocytes
  • T CELLS

13
T lymphocytes and cellular immunity
  • Attack and destroy
  • Produce cytokines that enhance specific immunity
    and non specific mechanisms of defense

14
T lymphocytes
15
T lymphocytes
  • Cytotoxic T cells destroy virally infected
    cells and tumor cells
  • Helper T cells they divide rapidly and secrete
    cytokines
  • Memory T cells They are antigen specific cells
  • Regulatory T cells( suppressor T cells) Cell
    mediated immunity
  • Natural Killer Cells Connects the innate and
    the adaptive immune system
  • Other subsets of cells

16
Natural Killer Cells( Doc Kaiser Microbiology)
17
Apoptosis( Doc Kaiser Microbology)
18
MHC - 1
  • Endogenous antigens, such as viral proteins, pass
    through proteasomes where they are degraded into
    a series of peptides.2. The peptides are
    transported into the rough endoplasmic reticulum
    (ER) by a transporter protein called TAP.3. The
    peptides then bind to the grooves of newly
    synthesized MHC-I molecules.4. The endoplasmic
    reticulum transports the MHC-I molecules with
    bound peptides to the Golgi complex.5. The Golgi
    complex, in turn, transports the MHC-I/peptide
    complexes by way of an exocytic vesicle to the
    cytoplasmic membrane where they become anchored.
    Here, the peptide and MHC-I/peptide complexes can
    be recognized by CTLs by way of TCRs and CD8
    molecules having a complementary shape.

19
MHC I and viruses
20
Humoral immunity
  • The result of circulating immunities
  • When stimulated by an antigenm the B lymphocytes
    initate a process that leads to the release of
    antibodies
  • Most effective at defending the body against
    viruses and bacteria
  • Works on the basis of
  • Specificity
  • Diversity
  • Memory
  • Self vs. Non self

21
Humoral immunity
  • Dependent upon the ability of white blood cells
    to recognize specific antigens
  • Antigens are generally exposed on the outer
    surface of a pathogen or are toxins

22
Antibody Response
  • Each B cell carries an antibody on its outer
    membrane
  • It has the ability to bind to a specific antigen
  • The binding of an antigen sensitizes or activates
    the B cells
  • This causes the cells to divide may times
  • The B cell divides to produce
  • Plasma cells that actively produce antibodies at
    a rapid rate
  • They also produce a memory cell that retains the
    information necessary to produce the antibody

23
B cells
  • After the binding of the antigen to the antibody,
    the B cells processes the antigen, by breaking it
    into tiny fragments
  • The fragments bind to molecules on the surface of
    the B cell MHCII

24
APC( Antigen Presenting Cell)
25
Antigen Presentation and MHC II
  • The antigen is presented on the surface of the B
    cell by MHC II
  • The T cells are activated to produce interleukin
    2
  • The activation further stimulates the production
    of more B cells - memory cells

26
MHC I and II
27
There are five classes of Immunoglobulins - The
basic form of antibodies
  • IgG
  • IgA
  • IgM
  • IgD
  • IgE

28
Basic structure
  • Basic unit is a Y shaped structure
  • They are composed of four polypeptide chains
  • The chains are held together by disulfide bonds
  • They possess both variable and constant regions

29
IgG
  • IgG-The main class of antibodies
  • Produced as a secondary response
  • Attach to antigens on microorganisms and their
    receptors attach to phagocytic cells
  • They work effectively with phagocytic cells
  • The tails section also activates complement
  • Crosses the placenta

30
IgM
  • Pentameric structure( secreted by Plasma cells)
  • Monmeric on the surface of B cells
  • It is the first antibody made in response to an
    infection
  • It has ten antigen binding regions
  • Activates complement and causes clumping of
    microbes

31
IgA
  • Occurs in bodily secretions
  • Found in breast milk
  • Attaches to the lining of the digestive,
    respiratory, and gastrointestinal tract
  • Transported through epithelial cells
  • Attaches to microbes before they invade tissues
  • Activates complement
  • Exists as a dimer

32
IgD
  • Found primarily on the membranes of B cells
  • It may help in immune responses
  • It also may be active in allergic responses

33
IgE
  • Has specially affinity for receptors on the
    basophils
  • In the blood or mast cells in the tissues
  • When IgE binds to antigens, the associated B
    cells secrete specific molecules that are related
    to allergic responses
  • Histamine is one of these molecules
  • IgE is found primarily in tissues and bodily
    fluids

34
Immune Disorders- SCIDS
35
SCIDS
  • Most cases of SCID are due to mutations in the
    gene encoding the common gamma chain (?c),
  • A protein that is shared by the receptors for
    InterleukinsIL-2, IL-4, IL-7, IL-9 and IL-15.
  • These interleukins and their receptors are
    involved in the development and differentiation
    of T and B
  • Another well-known form of SCID is caused by a
    defective enzyme, adenosine deaminase (ADA),
  • Necessary for the breakdown of purines. Lack of
    ADA causes accumulation of dATP.
  • This metabolite will inhibit the activity of
    ribonucleotide diphosphate reductase, the enzyme
    that reduces ribonucleotides to generate
    deoxyribonucleotides

36
Genetic Diseases of the Immune System
  • Severe combined immunodeficiency
  • Multiple types
  • X linked and autosomal
  • Affect both cellular and humoral aspects of the
    immune system
  • T cell-negative (T-), B cell-negative (B-),
    natural killer cell-positive (NK)
  • Gene map locus 11p13, 11p13
  • SCIDS

37
Immune Disorders
38
Immune disorders
  • 301000, WISKOTT-ALDRICH SYNDROME WAS
  • The manifestations of Wiskott-Aldrich syndrome
    are eczema, thrombocytopenia, proneness to
    infection, and bloody diarrhea.
  • Death usually occurs before age 10 years.
  • Bone Marrow transplants are a treatment
    possibility

39
Genetics of Immunoglobulins
40
Generation of Immunoglobulins
41
Genetics of Immunoglobulins
  • Genes for the constant region
  • Genes for the variable region
  • Light and heavy chained molecules are synthesized
    separately
  • The diversity of antibody-binding sites comes
    from the random combinations of variable gene
    segments that join with constant gene segments

42
Naturally Acquired Active immunity
  • The immune system responds to an invader by
    producing antibodies and activated lymphocytes
  • This can produce a life long immunity

43
Naturally Acquired Passive Immunity
  • Antibodies transferred across the placenta to the
    fetus
  • Transfer of antibodies through the colostrum in
    the breast milk
  • Both of these provide temporary immunity to an
    infant

44
Artificially Acquired Passive Immunity
  • When antibodies made by other hosts are
    introduced into a new host
  • An example of this is rattlesnake antivenin
    injection
  • Antivenins are antibodies produced by other
    animals such as horses or cows
  • The host does not make new antibodies - the
    antibodies supplied circulate for as long as a
    month and are eventually destroyed in the host

45
Venom
  • Rattlesnake venom is a mixture of enzymes that
    possess the ability to destroy cells
  • Can be a neurotoxin as well
  • Injected like a hypodermic

46
Antivenin
  • Antivenin is a polyvalent preparation of
    globulins prepared by the fractionation of
    horses serum
  • It is a mixture of globulins from different types
    of rattlesnakes

One of antigens in rattlesnake venom
47
Artificially Acquired Active Immunity
  • When an individual is exposed to a vaccine
  • The vaccine might include attenuated
  • ( weakened) organism, portions of the organism,
    toxins, subunits of antigenic portions of the
    organism

48
Chicken Pox Varicella Zoster
  • Chickenpox begins as a cold
  • Sneezing, coughing, and a runny nose
  • Two days later a rash begins
  • Usually begins on the chest and face
  • It may spread all over the body

49
Chicken Pox
  • Infection spread by aerosolized droplets
  • It is contagious 1-2 days prior to the onset of
    symptoms
  • It takes 20 days to develop symptoms
  • It takes 5-10 days for the immune system to
    defeat the virus

50
  • All children between 12 and 18 months of age
    should have one dose of chickenpox vaccine.
  • Children who have had chickenpox do not need the
    vaccine.
  • No tests need to be administered to determine
    immune status - a parent's recollection of the
    disease is considered a reliable measure of
    previous infection and therefore immunity.?
  • Children between 19 months and their 13th
    birthday who have not had chickenpox should be
    vaccinated with a single dose.?People 13 and
    older who have not had chickenpox should get two
    doses of the vaccine 4 to 8 weeks apart.

51
Primary Immune Response
  • In humoral immunity the primary response occurs
    when the antigen is first recognized by host B
    cells
  • B cells divide to form plasma cells
  • Antibodies begin to appear - IgM
  • Cytokines trigger the proliferation of B cells
  • IgG synthesis accelerates
  • Memory cells are formed

52
Secondary Response
  • The secondary response occurs when the immune
    system sees an antigen for the second time
  • Memory cells divide more rapidly than B cells
  • IgM is still produced first, but in smaller
    quantities than the secondary response
  • IgG is produced second, but in greater amounts

53
Response of B cells
  • T independent antigens - This response only
    produces IgM and no B memory cells are formed
  • T- dependent antigens - B cell becomes the
    antigen presenting cell, makes contact with the T
    helper cell and the T helper then produces
    lymphokines that stimulate thethe B cell to
    differentiate

54
Primary and Secondary
55
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56
Inactivation of the antigen( microbe)
  • Neutralization - IgG is the main neutralizer of
    these infections
  • Prevents the toxin from doing further damage
  • Antibiotics are required to kill the microbe
    causing the infection
  • Viruses can be inactivated by neutralization
  • Viruses with envelopes can be removed by
    complement

57
Neutralization Reaction http//people.eku.edu/ritc
hisong/neutralization2.gif
58
Neutralization of a toxin
59
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60
Agglutination reactions
  • Bacteria are large particles
  • When they react with bacteria they can clump
  • IgM causes strong agglutination reactions
  • IgG also causes agglutination

61
Ingestion by macrophages
  • Both agglutination and neutralization effectively
    inactivate the microbe by binding to the
    antigenic site
  • Macrophages can then ingest the pathogen

62
COMPLEMENT
  • Pathway for the elimination of microbes
  • Cascade
  • Lysis of cells
  • Augmentation of immune response
  • Disposal of waste by products

63
Complement action
  • Perforin is a cytolytic protein found in the
    granules of CD8 T cells and NK. Upon
    degranulation, perforin inserts itself into the
    target cell's plasma membrane forming a pore
  • This finally results in the lysis of a cell

64
Classical Complement Pathway
65
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