Regulation of allergic reactions by aerobic Corynebacterium equi extract, CEF. II. Inhibition of Heterologous PCA and antigen-induced histamine release in rats.

A water-soluble fraction (CEF) obtained from Corynebacterium equi was administered intradermally or intravenously into Sprague-Dawley rats. Passive cutaneous anaphylaxis (PCA) was elicited in these rats along with the controls by sensitization with mouse anti-DNP serum and challenge with the corresponding antigen. PCA reactions were markedly inhibited by the pretreatments of the rats with CEF. Similar treatments of the animals 2-4h after the sensitization did not inhibit PCA. Inhibitory activity of CEF in the pretreated animals was shown to be dose-dependent. Incubation of rat peritoneal mast cells with CEF effectively blocked the binding of murine IgE antibodies to the cells as evidenced by the failure of the treated cells to bind the antibodies. Furthermore, antigen-induced histamine release from rat mast cells, which were sensitized with murine IgE antibodies, was reduced significantly by CEF treatment of the cells prior to the sensitization. Results of this study indicated that CEF inhibits the PCA in rats, presumably by blocking the binding of heterocytotropic antibodies to Fc receptor of mast cells.