What Are the Body's Primary and Secondary Responses?

The human body's primary and secondary responses refer to the immune system's ability to defend against foreign entities, such as disease, virus or bacteria. The primary response is the body's first line of defense, and the secondary response is the human body's last attempt to oust an invading entity.

Primary Response

• As the first line of defense, the body triggers the primary immune response when a harmful antigen is detected. An antigen is a substance or molecule that, when introduced to the body, triggers the production of antibodies by the immune system. The antibodies then try to kill or neutralize the antigen identified as a dangerous or foreign entity. A lag period of 10 days to four week, occurs after the antigen enters the body before antibodies are produced and released.

Primary Response II

• During the lag phase, B-lymphocytes prepare to do their sole job of dividing and producing antibodies, specifically designed to destroy harmful antigens. The antibodies will appear in the bloodstream and increase until they level off and slowly decrease when the original antigens are not present in the body. As the primary immune response progresses, the quality of antibodies will improve.

Secondary Response

• The secondary immune response occurs after an antigen the body has previously encountered invades the body again. However, the antigen must be the same virus or bacteria and the same exact strain. An example would be a person being reinfected with the exact same flu. The body's previous antibodies created specifically for the strain of flu virus would increase without any lag perceiving the antigens as a greater threat.

Secondary Response II

• After the antigen has been successfully killed off again, the body's antibodies will fall even lower than in the previous encounter. Only the most dominant antibodies will survive, and they will relax into memory mode, in case the exact strain of virus is ever encountered again.