Preferential differentiation of inflammatory cells by recombinant human interleukins

The effects of recombinant human interleukins (IL) on hematopoiesis were explored by using suspension cultures of mononuclear cells of human umbilical cord blood and bone marrow cells. The results showed that IL-5 induced the selective differentiation and proliferation of eosinophils. After 3 weeks in culture with IL-5, over 90% of nonadherent cells in both bone marrow cell and cord blood cell cultures became eosinophilic myelocytes. Culture of the same cells with IL-4 resulted in the selective growth of OKT-3⁺ lymphocytes. In suspension cultures of bone marrow cells and cord blood cells grown in the presence of IL-3, basophilic, eosinophilic, and neutrophilic myelocytes developed within 2 weeks. By 3 weeks, however, the majority of non-adherent cells became eosinophilic myelocytes. In contrast to mouse bone marrow cell cultures, neither IL-3 nor combination of IL-3 and IL-4 induced the differentiation of mast cells in human bone marrow or cord blood cell cultures.