A regulatory role for Fc gamma receptors (CD16 and CD32) in hematopoiesis

Progenitor cells of the T- and B-lineages in mice express (CD32) and Fc gam ma RIII (CD16) but as the developing lymphocytes begin to express clonal an tigen receptors, CD16 and CD32 are downregulated in T-cells, and CD16 is do wnregulated in B-cells. Considering that counter-receptors for Fc gamma R o ccur on thymic and bone marrow stromal cells, the possibility exists that F c gamma R might participate in some aspect of T- and B-lineage development prior to the stage of antigen receptor expression. Previous studies provide d evidence that Fc gamma R can influence murine T-lineage development. In t he present studies we found that anti-Fc gamma RII/III mAb accelerated B-li neage development in bone marrow cultures from normal mice, but not in cult ures from CD16-/- or CD32-/- mice. Similar results were observed when FACS- purified B-progenitor cells were co-cultured with BMS2, a bone marrow strom al cell line. Fresh bone marrow from CD32-/- mice contained about two-fold more B-lineage cells compared to bone marrow from normal or CD16-/- mice. T hese studies indicate that the Fc gamma R on B-lineage progenitor cells can influence their further development and add to a growing body of evidence that implicates Fc gamma R as regulatory elements in hematopoiesis. (C) 199 9 Elsevier Science B.V. All rights reserved.