Читать книгу Immunology - Richard Coico - Страница 115

The first exposure of an individual to an immunogen is referred to as the primary immunization, which generates a primary response. As we shall see in subsequent chapters, many events take place during this primary immunization: cells process antigen, triggering antigen‐specific lymphocytes to proliferate and differentiate; T‐lymphocyte subsets interact with other subsets and induce the latter to differentiate into T lymphocytes with specialized function; T lymphocytes also interact with B lymphocytes, inducing them to synthesize and secrete antibodies.

A second exposure to the same immunogen results in a secondary response. This may occur after the response to the first immune event has leveled off or has totally subsided (within weeks or even years). The secondary response differs from the primary response in many respects. Most notably and biologically relevant is the much quicker onset and the much higher magnitude of the response. In a sense, this secondary (and subsequent) exposure behaves as if the body remembered that it had been previously exposed to that same immunogen. In fact, secondary and subsequent responses exploit the expanded number of antigen‐specific lymphocytes generated in response to the primary immune response. Thus the increased arsenal of responding lymphocytes accounts, in part, for the magnitude of the response observed. The secondary response is also called the memory or anamnestic response, and the B and T lymphocytes that participate in the memory response are termed memory cells.