DE-NOVO DEVELOPMENT AND SELF-REPLENISHMENT OF B-CELLS

Previous studies distinguished two murine B cell lineages: the convent ional lineage, which comprises the majority of B cells, and the Ly-1 a lineage (B-1a), which represents a small percentage of total adult a cells. A third subset, B-1b cells, shares many properties with B-1a ce lls, including the characteristic ability to self-replenish, but does not express Ly-1 (CD5). Reconstitution studies presented here show tha t (i) although the B220(-) population in adult spleen and bone marrow contains very little progenitor activity for B-1a cells, it can recons titute roughly half the normal number of B-1b cells; (ii) B-1 progenit ors present in adult bone marrow and spleen function at low levels in adult animals; (iii) peritoneal B-1 cells (principally B-1b) that deve lop following bone marrow transfer, like B-1 cells from normal animals , are capable of substantial self-replenishment; and (iv) conventional B cells do not expand (self-replenish) in adoptive recipients, althou gh they can persist for long periods, Collectively, these progenitor a nd self-replenishment characteristics provide a developmental base for distinguishing B-1a, B-1b and conventional B cells,