Janeway Figure 7.40. Proposed population dynamics of conventional B cells. B cells are produced as receptor-positive immature B cells in the bone marrow. The most avidly self-reactive B cells are removed at this stage. B cells then migrate to the periphery where they enter the secondary lymphoid tissues. It is estimated that 1020 Ã— 106 B cells are produced by the bone marrow and exported each day in a mouse, and an equal number is lost from the periphery. There seem to be two classes of peripheral B cell: long-lived B cells and short-lived B cells. The short-lived B cells are, by definition, recently formed B cells. Most of the turnover of short-lived B cells might result from B cells that fail to enter lymphoid follicles. In some cases this is a consequence of being rendered anergic by binding to soluble self antigen; for the remaining immature B cells, entry into lymphoid follicles is thought to entail some form of positive selection. Thus the remainder of the short-lived B cells fail to join the long-lived pool because they are not positively selected. About 90% of all peripheral B cells are relatively long-lived mature B cells that appear to have undergone positive selection in the periphery. These mature naive B cells recirculate through peripheral lymphoid tissues and have a half-life of 68 weeks in mice. Memory B cells, which have been activated previously by antigen and T cells, are thought to have a longer life.
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|current||20:08, 10 March 2004||461 × 343 (14 KB)||Tarek||Janeway Figure 7.40. Proposed population dynamics of conventional B cells. B cells are produced as receptor-positive immature B cells in the bone marrow. The most avidly self-reactive B cells are removed at this stage. B cells then migrate to the periphe|
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