A subpopulation of B220+ cells in murine bone marrow does not express CD19 and contains natural killer cell progenitors

Abstract

Bone marrow of both normal and rearrangement-deficient mice contains a small population of B220 (CD45R)+ cells, which do not express the B lineage marker CD19. Instead, part of this population coexpresses the surface marker CD43 and lacks or expresses very low levels of heart stable antigen (HSA) and BP-1, thus representing a part of Hardy's fraction A (B2201-CD43+ HSA, BP- 1) of B lineage development: However, some 20-40% of these B220+-CD19 cells also coexpress the NK1.1 surface molecule and do not express genes like V(preB) or B29 restricted to the B cell lineage. These cells respond to recombinant interleukin-2 in vitro, and develop into killer cells that can lyse the prototypic NK target tumor cells, YAC-1, as well as syngeneic normal lipopolysaccharide or concanavalin A blasts, providing they lack the surface expression of major histocompatibility complex class I molecules. The implications of these findings for studies on B lymphopoiesis are discussed. It is suggested that the CD19-specific monoclonal antibody is more reliable, as in humans, than B220(CD45R) to detect B lineage cells in mice.