Mast cells produce ifn-γ in response to IL-I2 stimulation, but not in response to antmge mediated activation

IL-12 is a potent inducer of IFN-γ production by T cells and NK cells. We examined whether purified rat peritoneal mast cells (PMC) are capable of secreting IFN-γ in response to IL-12 or anti-IgE activation. PMCs were obtained by peritoneal lavage of Brown Norway rats, and purified (>93%) on a 30%/80% Percoll gradient. PMCs (lxlO/ml) were resuspended in RPMI 1640 media + 5% FBS and incubated at 37°C for 24 hr with or without activating agent. IFN-γ was assayed in supernatant using an ELISA, sensitive to 2.35-4.03 VIml. Mast cells stimulated with rmIL-12 produced significant IFN-γ above media control in a dose dependent manner. A mean of 8.0S±3.11 U/ml IFN-γ was detected when PMCs were stimulated with 2 U/ml IL-12 (p<0.01, n=4). IFN-Y production was not detected until after 6 hr of incubation, and continued to increase until 24 hr. IL-12 induced IFN-γ production was significantly inhibited in the presence of 0.1 pM PGE, or 5 ng/ml IL-10 to 40±3 and 71 ±8% respectively (p<0.05, n=4), compared to cells treated with IL-12 alone. When PMCs were stimulated with anti-IgE for 10 minutes, 24.7±5.17 of total histamine was released. However, when the same cells were further incubated for 24 hr with anti-IgE, no IFN-γ was detected (n=4). Cytospin preparations of PMCs stimulated with 2 U/ml IL-12 showed significant immunoreactivity for IFN-γ. The 1FN-7 derived from PMCs was biologically active as it was capable of inducing class n expression on the moule intestinal epithelial cell line, MODE-K. These studies could have important implications for the role of mast cells in infection and inflammation. [Supported by the MRC of Canada.].