GRANULOCYTE-MACROPHAGE COLONY-STIMULATING FACTOR PLAYS A ROLE IN THE FUNCTIONAL-ACTIVITY OF MAST-CELLS

A peptide homologous to a region of murine granulocyte-macrophage colo ny-stimulating factor (mGM-CSF), P27-38, which was shown to be a GM-CS F antagonist, inhibited the function of serotonin release from murine mast cells. Peptide P27-38 inhibited immunoglobulin E (IgE)-mediated s erotonin release in a dose-dependent manner when induced by either spe cific antigen or anti-IgE antibody. In contrast, non-receptor-mediated release of serotonin by agents such as compound 48/80 or the calcium ionophore A23187 were not affected by the GM-CSF antagonist. Similar e ffects were observed with GM-CSF-neutralizing antibodies. The inhibito ry effect of P27-38 and the neutralizing antibodies on serotonin relea se could be reversed by the addition of exogenous GM-CSF to the stimul ated mast cells, indicating that the inhibitory activity was probably due to an effect on endogenously produced GM-CSF. These findings sugge st that GM-CSF produced by stimulated mast cells is involved in the re gulation of their activity in an autocrine manner.