Interleukin-4 production by Fc epsilon R+ cells

Among non-B, non-T cells in the spleen and among unfractionated bone marrow cells, there is a population of cells that are capable of producing IL-4 in response to cross-linkage of FC epsilon RI or Fc gamma RII. Their IL-4-producing capacity is strikingly enhanced by treatment of the cells or of the animals donating such cells with interleukin-3 (IL-3). Fc epsilon R+ cells constitute 1-2% of splenic non-B, non-T cells and of bone marrow cells from normal donors but they contain all the capacity to produce IL-4 in response to cross-linkage of Fc epsilon RI or Fc gamma RII or to treatment with ionomycin. Fc epsilon R- cells fail to make such responses. Electron-microscopic analysis indicates that virtually all the granulated or vacuolated Fc epsilon R+ cells are of the basophil lineage. However, it has not yet been resolved whether these cells or immature mast cells, presumably in the Fc epsilon R+ granule/vacuole-negative cell population, are the principal producers of IL-4 in response to these stimuli.