Human bone marrow non-B, non-T cells produce interleukin 4 in response to cross-linkage of Fce and Fcy receptors

Human bone marrow (BM) cells lacking T-and B-cell markers expressed RNA encoding interleukin (IL) 4 and secreted detectable amounts of IL-4 in supernatants in response to Fce or Fcy receptor (FceR or FcyR) cross-lng. In some experiments, IL-S RNA expression in response to FcER cross-linkage could alo be detected. In contrast, RNA tran-scripts for, and secretion of, IL-2, IL-6, and interferon y were never observed. The presence of IL-3 in the cultures was essential for IL-4 production by non-B, non-T BM cells in response to FcyR cross-linking and enhanced IL-4 RNA expression in response to FceR cross-linking. Under the same experimental conditions, BM T and B lymphocytes, as well as peripheral blood T. B, and non-B, non-T cells, did not express IL-4 RNA. Prolonged incubation of non-B, non-T celis in IgE-free medium followed by extensive washing did not inhibit IL4 production induced by anti-IgE antibodies, sgsting that the FceR involved in the response has the characteristics of a high-affinity receptor. The FceR' celis were separated from the FceR- cells by sorting non-B, non-T BM cell suspensions with fluorescein isothiocyanate-conjugated IgE and then assesse for both IL-4 RNA expression and alcian blue staining. IL4-producing and alcian blue-positive celis segregated with the These data suggest that cross-linkage. Non-B, non-T BM cells were sensitized with IgE (1 pZg/ml) and then cultured for 48 hr with anti-IgE antibody (3 Ag/ml). Dot blot analysis of IL-4 RNA expression was performed as described in Materials and Methods. IL-4 present in culture supernatants was measured by a commercial ELISA.