Adaptive/Acquired Immunity

• lymphocytes

  • pathogen-specific recognition ability
  • WBC produced in bone marrow
  • 3 types:

  1. B cell

  - Remain & mature at bone marrow

  2. T cell

  - Migrate from bone marrow  thymus until maturity

  3. Natural killer cells (part of innate immunity)
• B & T cell antigen receptors

  • On the surface of B/T cells
  • Recognizes antigen

  - Any substance that elicits an immune response

  - Usually small protruding parts of viruses and bacteria

  - Could be in the form of toxins released on body fluids

  - Epitope - part of antigen where antigen receptors of lymphocytes attach to

  • 100,000 antigen receptors – on 1 B/T cell
• Recognition – binding of antigen receptor of a B/T cell to an antigen
• Antigen recognition by B cells

  • Antigen receptor of B cell binds to epitope of antigen
  • B cell secretes a soluble form of antigen receptor (aka antibody/immunoglobulin)
  • Antibodies recognize epitopes of antigens on a pathogen’s surface/even freely floating antigens on body fluids (blood/lymph)
• Antigen recognition by T cells

  • Antigen receptors of T cells bind to fragments of pathogens displayed on surface of infected cell

  - Antigen binds to an MHC molecule inside the infected cell

  - MHC molecules displays antigen on the surface of infected cell

  • After binding, T cell can identify the cell as infected & the pathogen
• Characteristics of Adaptive Immunity

  1. Rich diversity of lymphocytes & antigen receptors

  --> Explains our immunity to a variety of pathogens

  2. Self-tolerance or lack of reactivity against own molecules & cells

  --> self-reactive lymphocytes (those with antigen receptors specific to body’s own molecules) are destroyed by apoptosis

  3. Cell proliferation triggered by activation increases B & T cells

  4. Immunological memory – stronger & more rapid response to an antigen encountered before
• 4. Immunological memory – stronger & more rapid response to an antigen encountered before

  2 types of B & T cells are produced :

  1. Effector cells – short-lived lymphocytes which immediately act against pathogen

  • Helper T cells, cytotoxic T cells – produced by T cells
  • Plasma cells – produced by B cells

  2. Memory cells – long-lived; reactive when pathogen infects body again

  • Memory T cells
  • Memory B cells
• Adaptive Immune Response

  A) Antigen

  B) B

  C) Cytotoxic T

  D) Helper T

  E) memory

  F) Plasma

  G) Memory B

  H) Memory Cytotoxic T

  I) Active Cytotoxic T

  
• 4. Immunological memory – stronger & more rapid response to an antigen encountered before

  • Saves time in cloning T/B cells
  • Primary immune response
  • Secondary immune response --> Stronger & more rapid response
• 1. Humoral immune response

  • Against antigens freely floating in body fluids
  • By B cells

  2. Cell-mediated response

  • Against antigens in infected cells
  • Carried out by T cells

  A) B

  B) T

  C) Thymus

  D) Plasma Cells

  E) B memory

  F) T Helper

  G) T Killer

  H) T Memory

  I) Yes

  J) No

  K) Antibodies

  L) cells

  M) Cytotoxic

  N) cells

  
• 1. Humoral immune response

  Actions of antibodies from activated B cells:

  1. Neutralization – binding of antibodies to the protein on surface of

  pathogen prevents pathogen from infecting body cells

  2. Opsonization – antibodies present pathogen for phagocytosis by

  neutrophils
• 2. Cell-mediated immune response

  • T cells use toxic proteins to kill cells infected by viruses/intracellular pathogens --> trigger apoptosis