INHIBITORY EFFECT OF VASOACTIVE INTESTINAL POLYPEPTIDE AND KETANSERINON ESTABLISHED ALLERGIC CONTACT-DERMATITIS IN MAN

Neuromediators may influence the immune response. To investigate their potential immunomodulating role in established allergic contact derma titis in man, the following neuromediators were tested: vasoactive int estinal polypeptide (VIP), serotonin, and the serotonin antagonists ke tanserin, methiotepine and ICS-205-930. Positive patch test reactions were elicited by application of nickel sulphate for 48 h. The neuromed iators were applied under patch test conditions after another 24 h. Th e test areas were measured before and 24 h after application of the ne uromediators and biopsy specimens were taken for immunohistochemistry. After application of VIP at a concentration of 10(-5) mol/l, and of k etanserin at a concentration of 10(-4) mol/l, there was a significant reduction in the diameter of the test reaction. In addition, with VIP there was a reduction in the number of Leu 3a+ cells. Also tested was the influence of the neuromediators on the proliferative response of p eripheral blood mononuclear cells from nickel-allergic subjects to nic kel sulphate. The cells were cultured for 6 days and the neuromediator s were added after 3 days. There was no effect on the proliferative re sponse, except for slight inhibition by serotonin and by ketanserin at 10(-4) mol/l. More interferon gamma was found in the supernatants whe n VIP was added at 10(-5) and 10(-6) mol/l than in the control culture s. Thus, VIP and ketanserin may have an inhibitory effect on establish ed allergic contact dermatitis. The effect of VIP is possibly mediated by an increased production of interferon gamma.