Synthetic retinoids inhibit histamine release from isolated human mast cells

In view of the immunomodulating properties of the synthetic retinoids etretinate and isotretinoin, their effects on isolated human mast cells were investigated. At concentrations of 10(-6) to 10(-5) M, isotretinoin and at 10(-6) M to 5 X 10(-5) M, etretinate inhibited concanavalin-A induced histamine release dose-dependently. Effective concentrations corresponded to achievable levels under therapeutic conditions in man. Without any additional stimulant, both drugs exhibited no appreciable effects with the exception of a toxic damage at very high levels.