Pathogenicity : the ability to cause disease

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• Pathogenicity the ability to cause disease
  
• in a host

• Virulence the degree of pathogenicity

• Nonspecific Defense Mechanisms
• defense that protect us from any pathogen

• Specific Defense Mechanisms (or immune
• response) defense that the body offers
• against a particular pathogen

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Nonspecific Defense Mechanisms
Specific Defense Mechanisms
1st line of defense
2nd line of defense
3rd line of defense

• Specialized lymphocytes
• B cells and T cells
• Antibodies

• Intact skin
• Mucous
• membranes
• and their
• secretions

• Phagocytic white
• blood cell
• Inflammation and
• fever
• Antimicrobial
• substances
• (complement system,
• interferon)

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Immunity
Specific defensive response when a host is
invaded by foreign organisms or other foreign
substances
Immune system
Cells, organs and molecules responsible for
immunity
Immune response
Collective response of immune system to foreign
substances
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Immunology
Vaccine (vaccinus from cow) 1798
Vaccination
Induce immunity to Infectious diseases
Eradicate from the world in 1980
Smallpox
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Specific immunity (the immune response)
Acquired immunity
Natural
Artificial
Active
Passive
Active
Passive
Preformed Ab in immune serum introduced into
body by injection
Ab pass from mother to fetus via placenta
Ag are introduced in vaccines body produces Ab
Antigens enter the body naturally
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The Duality of the Immune System
1. Humoral (antibody-mediated) immune system
involves the production of Antibodies by B cells
(B- lymphocytes) defends mostly against
bact., bact. toxin, and virus in bodys
fluids
2. Cell-mediated immunity involves the
production of specialized lymphocytes
called T cells effective against bact.
and viruses located within phagocytic or
infected host cells and against fungi, protozoa
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The cardinal features of immune responses
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Specificity, memory and self-limitation
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Phase of immune response
1. Recognition phase 2. Activation phase 3.
Effector phase
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Antibodies or Immunoglobulins (Igs) Proteins
that are made in response to an antigen and can
recognize and bind to that antigen
Antibody structure
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Immunoglobulin classes
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B Cells and Humoral Immunity
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The Activation of Ab-Producing Cells by Clonal
selection
Clonal selection hypothesis

• Every individual contains numerous
• distinct clones of lymphocytes.
• Antigen selects a specific pre-existing clone
• and activates it.

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T Cells and Cell-Mediated Immunity
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Types of T cells

• Helper T cells (TH) stimulate other
• cells of the immune system (TC , B cells)
• to fight off intruders

Cytotoxic T cells (TC) protect against
viral infections and intracellular infections.
They destroy target cells on contact.
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• Delayed T hypersensitivity T cells (TD)
• are associated with certain allergic
  reactions
• e.g. rejection of transplant tissues also
• important in defensive against cancer

• Suppressor T cells (TS) regulate immune
• response and help maintain tolerance

• Natural killer cells (NK) attack and
• destroy target cells, esp. virus-infected
• cells and tumor cells

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Application of Immunology
Vaccines
Diagnostic Immunology
Agglutination reaction
Neutralization reaction
Fluorescence antibody (FA) technique
Enzyme-Linked Immunosorbent Assay (ELISA)
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Hypersensitivity
Type I (Anaphylactic) reactions
Type II (Cytotoxic) reactions - hemolytic
disease of the new born

• Type III (Immune complex) reactions
• - serum sickness

Type IV (Cell-mediated) reaction - allergic
contact dermatitis
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Autoimmune Diseases
Immune Deficiency Diseases

• AIDS

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