Immunology

Immunology

1. The 'Immune Response'

   • 1. Initial recognition of foreign substances
     • 'non-sense' antigens
       • antigen: molecule that stimulates an immune response
       • e.g. bacteria
   • 2. Production of effector molecules and cells which eliminate the pathogens
     • Lymphocyte produce antibodies
       • antibody: specialised proteins produced by B-lymphocytes in respose to antigen

2. 4 Main Components

   • 1. A method of trapping and processing antigens
     • B-cell binds to foreign antigen receptor
   • 2. A mechanism for reacting specifically to the antogen
     • antigen receptors on cell surface of lymphocytes lead to a specific immune response
   • 3. Cells which can produce antibodies or which can participate in the cell-mediated immune response
   • 4. Cells to retain the memory of the event and to react specifically to the antigen in future encounters

3. T-cell recognition

   • APC's process antigens into smaller peptides for T-cell recognition
     • These segments are then expressed an the APC via the MHC II molecules for recognition by TCRs
       • TCR composed of two polypeptides which are both membrane anchored. (alpha and beta)
         • alpha and beta contain one constant and one variable domain
   • T-cell division
     • Helper
       • activates B-cells
         • B-cells divide into identical clones etc etc
           • clonal expansion
           • B-cells produce and secrete antibodies identical to original
             • antibodies circulate in serum and lymph
         • B-cells find to antigen - flagging it for destruction
     • Suppressor
     • cytotoxic

4. Internalising the antigen

   • antigen-antibody complex is engulfed into B-cell and partially digested
     • partial digestion - antigen is preserved intact
       • the antigen is then returned to the surface of the B cell and displayed on the surface
         • This allows the anitgen to be recognised by helper T-cells

5. Destruction of the antigen

   • label from B-cells attracts cytotoxic killer cells and will engulf the Ab/Ag complex

6. Immune Response

   • first exposure response = primary immune response
     • 7-10 day latent period
       • necessary time for the antigen to contact specific cells, for cell interaction, clonally expand and for B-cells to secrete sufficiant antibody
   • during the exponential phase - rapid increase of antibody concentration in plasma
     • only temporary
     • only memory B-cells retained
       • key for secondary response (2nd innoculation)
         • latent period much shorter (less than 3 days)
           • antibody production much greater