B‐1 cells: the lineage question revisited

Summary: The origins and functions of B‐1 cells have sparked a good deal of controversy, largely centered on whether these B cells are developmentally distinct from the principal B cell populations (B‐2) found in peripheral lymphoid organs. However, the prime criteria for assigning B‐1 and B‐2 cells to separate developmental lineages are satisfied by studies published some time ago that 1) identify distinct sources of progenitors for B‐1 and B‐2 cells; 2) show that these progenitors express their inherent commitment developing under the same conditions in co‐transfer recipients; and, 3) have distinctive developmental patterns revealed by analysis of cells at various stages along the B‐cell development pathway. I review these developmental studies here both to clarify the issue and to set the stage for presentation of evidence from more recent studies, which further define the functional differences between B‐1 and B‐2 cells and reveal intriguing complexities in the selective and other mechanisms that control the VH composition of the B‐1 antibody repertoire.