Читать книгу Immunology - Richard Coico - Страница 24

Adaptive immune responses have historically been divided into two separate arms of defense: B‐cell‐mediated or humoral immune responses, and T‐cell‐mediated or cellular responses. Today, while we recognize that B and T cells have very distinct yet complementary molecular and functional roles within our immune system, we understand that the two arms are fundamentally interconnected at many levels. “Experiments of nature,” a term coined by Robert A. Good in the 1950s when describing the immune status of humans with a congenital mutation associated with an athymic phenotype, have provided significant insights related to the interdependence of these two arms of the immune system. Athymic mice that fail to develop thymic tissue (a similar phenomenon in humans is called DiGeorge syndrome) results in a profound T‐cell deficiency with accompanying abnormalities in B‐cell function. The molecular explanation for the latter is now well understood. Without T‐cell help, B cells are unable to generate normal antibody responses and, in particular, to undergo immunoglobulin class switching (see Chapter 9). The help normally provided by T cells is delivered in several ways, including their synthesis and secretion of a variety of cytokines that regulate many events in B cells required for proliferation and differentiation (see Chapter 11).