Abstract
Interleukin-1 alpha (IL-1α) and beta (IL-1β) are well known factors that stimulate hematopoiesis, nevertheless there are reports that show that they can also inhibit this activity. While both IL-1α and IL-1β induce the expression of hematopoietic cytokines, such as growth factors and their receptors on myeloid cells, helping thus to regulate hematopoiesis, it is not known if their inhibitory activity is also mediated through the induction of other specific cytokines. In this work we show that recombinant human IL-1β (rhIL-1β) inhibits the proliferation of a mouse IL-3-dependent myeloid multipotent cell line (32D cl3), without inducing its differentiation. We show that rhIL-1β induces in 32D cl3 cells the expression of the tumor necrosis factor alpha (TNF-α) gene, a well known growth inhibitor, and that the rhIL-1β growth inhibition property on 32D cl3 cells is partially due to this secreted TNF-α, hinting thus that the inhibition of hematopoiesis by IL-1 is mediated through other induced cytokines.