Hematopoietic activities of interleukin 1.

IL-1 is perhaps the most pleiomorphic of the cytokines. Only recently however has it been suspected that IL-1 has effects in stimulating hematopoiesis. Its principal effect in this regard seems to be stimulation of pluripotent stem cells, causing these cells to then respond to lineage-specific growth factors. Thus, although IL-1 does not function directly as a colony stimulating factor, it synergizes with G-CSF, GM-CSF, and IL-3. Indeed, biochemical and serological evidence suggests that IL-1 accounts totally for the biological activity previously termed hemopoietin-1 which has been shown to play a central role in the regulation of hematopoiesis.