Mouse splenic and bone marrow cell populations that express high-affinity Fc6 receptors and produce interleukin 4 are

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 Fc6 receptors (Fc6R) or Fc,,R or to ionomycin. Isolated FceR' 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 FcER' cells are shown to be enriched in cells that contain histamine and express alcian blue-positive cytoplasmic granules. By electron microscopy, the vast major- ity of cytoplasmic granule-containing cells are basophils; they constitute -25 % and -50%, respectively, of Fc,R' spleen and bone marrow cells from anti-IgD-injected mice. The FcER- populations contain cells that form colonies typical of mast cells. The Fc,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,R- populations) the colonies are small, and all the cells die within 2-3 weeks. The Fc,R' cells synthesize histamine during a 60-hr culture with IL-3, while the Fc,R- cells do not. These results indicate that IL-4-producing Fc,R' cells are highly enriched in baso- phils.