Inhibition of histamine release from human lung and rat peritoneal mast cells by cyclosporin-A

Cyclosporin A (CS-A) partly inhibited IgE-mediated histamine release from human lung tissuein vitro (chopped and collagenase-dispersed preparations). Inhibition started at concentrations within the clinical blood level of the drug, but the IC₅₀ was much higher (10–50 M; 50% inhibition reached only in some experiments). CS-A also inhibited histamine release from rat peritoneal mast cells (RPMC) induced by antigen, concanavalin-A (Con-A), compound 48/80 and ionophore A23187. The IC₅₀ values were 0.3, 23.0, and 33.0 M for Con-A, A23187 and ovalbumin respectively. Inhibition of 48/80-induced release did not reach 50%. By comparison with human basophils the human lung and RPMC were less sensitive to the inhibitory action of CS-A. The IgE-mediated Schultz-Dale reaction in human lung strips was slightly and inconsistently inhibited by CS-A, but IgG₁-mediated reaction in guinea-pig lung strips was potentiated by the drug.