MOUSE SPLENIC AND BONE-MARROW CELL-POPULATIONS THAT EXPRESS HIGH-AFFINITY FC-EPSILON RECEPTORS AND PRODUCE INTERLEUKIN-4 ARE HIGHLY ENRICHED IN BASOPHILS

Splenic and bone marrow cells from normal mice, and from mice that have been polyclonally activated by injection of anti-IgD antibody, contain cells that produce interleukin 4 (IL-4) in response to crosslinkage of Fc-epsilon-receptors (Fc-epsilon-R) or Fc-gamma-R or to ionomycin. Isolated Fc-epsilon-R+ cells have recently been shown to contain all of the IL-4-producing capacity of the nonlymphoid compartment of spleen and bone marrow. Here, purified Fc-epsilon-R+ cells are shown to be enriched in cells that contain histamine and express alcian blue-positive cytoplasmic granules. By electron microscopy, the vast majority of cytoplasmic granule-containing cells are basophils; they constitute almost-equal-to 25% and almost-equal-to 50%, respectively, of Fc-epsilon-R+ spleen and bone marrow cells from anti-IgD-injected mice. The Fc-epsilon-R- populations contain cells that form colonies typical of mast cells. The Fc-epsilon-R+ populations also contain cells that, upon culture with IL-3, form colonies of alcian blue-positive cells, but (in contrast to colonies derived from Fc-epsilon-R- populations) the colonies are small, and all the cells die within 2-3 weeks. The Fc-epsilon-R+ cells synthesize histamine during a 60-hr culture with IL-3, while the Fc-epsilon-R- cells do not. These results indicate that IL-4-producing Fc-epsilon-R+ cells are highly enriched in basophils.