Antibodies are protein molecules processed by the immune system in response to allergens, Infectious organisms and allergens exhibit characteristic proteins called antigens. The immune system recognises and responds to antigens by generating corresponding antibodies.One or two weeks after initial exposure to HIV, antibodies to HIV antigens begin to appear in the blood, at concentrations which persist to increase for several more months. These antibodies persist for life, providing typical markers which can be identified by HIV screening tests. Neutralizing antibodies (NAbs) typically play a major role in controlling viral infections and contribute to the protective effect of many successful vaccines. Antibodies have the ability to block HIV-1 replication through multiple pathways, and they exert immune pressure on the virus that leads to escape.