Signals Provided By Thcell Cytokines

Although B cells stimulated with membrane proteins from activated TH cells are able to proliferate, they fail to dif ferentiate unless cytokines are also present; this finding suggests that both a membrane-contact signal and cytokine signals are necessary to induce B-cell proliferation and differentiation. As noted already, electron micrographs of T-B conjugates reveal that the antigen-specific interaction between a TH and a B cell induces a redistribution of TH-cell membrane proteins and cytoskeletal elements that results in the polarized release of cytokines toward the interacting B cell.

Once activated, the B cell begins to express membrane receptors for various cytokines, such as IL-2, IL-4, IL-5, and others. These receptors then bind the cytokines produced by the interacting TH cell. The signals produced by these cytokine-receptor interactions support B-cell proliferation and can induce differentiation into plasma cells and memory B cells, class switching, and affinity maturation. Each of these events is described in a later section.

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Essentials of Human Physiology

Essentials of Human Physiology

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