B Cell Development in the Spleen Takes Place in Discrete Steps and Is Determined by the Quality of B Cell Receptor–Derived Signals

TLDR

Mature B lymphocytes, which originate from short‑lived bone‑marrow precursors, are the only cells that enter splenic and lymph‑node follicles to mount an immune response. In the spleen, mature B cells are actively selected from two precursor populations—transitional type 1 cells that arrive from the bone marrow and transitional type 2 cells that proliferate in primary follicles—so that either lineage can give rise to mature B cells.

Abstract

Only mature B lymphocytes can enter the lymphoid follicles of spleen and lymph nodes and thus efficiently participate in the immune response. Mature, long-lived B lymphocytes derive from short-lived precursors generated in the bone marrow. We show that selection into the mature pool is an active process and takes place in the spleen. Two populations of splenic B cells were identified as precursors for mature B cells. Transitional B cells of type 1 (T1) are recent immigrants from the bone marrow. They develop into the transitional B cells of type 2 (T2), which are cycling and found exclusively in the primary follicles of the spleen. Mature B cells can be generated from T1 or T2 B cells.