THE IMMUNE RESPONSE

In specific immunity, cells in the body recognise the proteins on the surface of certain agents as foreign.

Lymphocytes are divided into three broad groups :

   B Cells recognise foreign agents and in time turn
   into plasma cells which produce the antibodies to
   fight disease. They absorb foreign antigens, break
   them into fragments and display them on their
   surface

   T_H Cells (T Helper Cells) bind to B cells which are
   displaying foreign antigens and release chemicals
   called lymphokines which change the B cells into
   plasma cells to start making antibodies.

   T_C Cells (Killer T Cells) bind to cells infected by a
   virus and release chemicals to destroy them before
   the viruses can be released

Antibodies are Y - shaped proteins with a variable region which binds specifically to certain antigens. Each antibody is directed against only one antigen. Antibodies help in immunity by :

●   Binding to receptors on the surface of disease agents and stopping them from entering host cells
●   Binding two or more agents together and inhibiting their function (agglutination)
●   Attracting the attention of passing immune cells which destroy the agent
●   Forming the basis of chemical complexes which disrupt the agents membrane (complement)

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