Regulation of IFN- production by rat peritoneal mast cells

Mast cells have been shown to be a potent source of a number of immunoregulatory cytokines. We have recently demonstrated that highly purified rat peritoneal mast cells (PMC) are capable of producing IFN-γ in response to recombinant murine IL-12 but not in response to anti-IgE activation. T-cell and NK cell production of IFN-γ has been shown to be inducible by a number of other agents and is not inhibited by treatment with Cyclosporin A. In the current study, we have examined the regulation of Brown Norway rat PMC IFN-γ production measured by a specific ELISA technique. PMC (1×10⁶ml) cultured for 24 hours with phorbol diester butyrate (10^-6M) in combination with ionomycin (10^-6M) or with rat recombinant TL-2 (100U/ml) and LPS (1mg/ml) failed to produce detectable levels of IFN-γ. Substance P activation of mast cells also did not induce IFN-γ production. However, mast cells stimulated with Cholera toxin (0.05/ig/ml) in the presence of ionomycin (10^-6M) produced a mean of 6.68±0.92 U/ml IFN-γ (n=4) significantly (p<0.05) higher than cells incubated in media alone. IL-12 induced PMC IFN-γ production was not inhibited or enhanced by concurrent treatment of the cells with anti-rat IgE, LPS, or recombinant rat IL-2. Similar to reports of T-cell and NK cells Cyclosporin A treatment did not inhibit IL-12 induced PMC IFN-γ production. However the response to IL-12 was completely abrogated by treating PMC in calcium free media. These observations suggest that mast cell IFN-γ responses to IL-12 have some similarities to those observed in T-cells however the range of IFN-γ inducing stimuli may be more restricted for mast cells than for other cell types.