Relationship Between Antigen and Antibody

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When an antigen first enters the body, only a few lymphocytes can recognize it. Antibodies increase within a few days and reach peak levels 1 or 2 weeks after exposure to the antigen.

In humoral immunity, antigen-antibody reactions are the basis of resistance to microbial invasion by the production of antibodies. Viruses or bacteria bind to the host cell's plasma membrane before invading a cell. Tears, nasal secretions, saliva, and other body fluids contain antibodies that bind to antigens on the surface of the infectious agent.

As a result, antibody-coated microbes cannot come in contact with host cells. If the microbial antigen is not recognized directly by T-lymphocytes, it is exposed to B-lymphocytes with the help of macrophages. In this condition, when B-lymphocyte binds to the antigen, it starts secreting antibodies.

Antibodies bind to antigens on the surface of bacteria to form antigen-antibody complexes and elicit an immune response.