IN-VIVO CIMETIDINE IMMUNOMODULATORY EFFECTS ON THE CUTANEOUS REACTIONTO OXAZOLONE IN THE CHICKEN

The effect of the histamine H-2-receptor antagonist, cimetidine, on th e cutaneous Arthus-like hypersensitivity to oxazolone elicited injecti ng subcutaneously oxazolone conjugated to egg-albumin (EA-OX) has been examined in the chicken. Cimetidine had opposite effects on the cutan eous reaction to oxazolone in relation to a different immunization sch edule. Cimetidine enhanced the cutaneous reaction to oxazolone obtaine d immunizing chickens with oxazolone dissolved in ethanol (Eth-OX); in stead cimetidine inhibited the cutaneous reaction obtained in chickens immunized with oxazolone dissolved in complete Freund adjuvant (CFA-O X). Optimum enhancement of the cutaneous arthus-like reaction to oxazo lone occurred when cimetidine was given for three consecutive days sta rting at the immunization. The enhancing effect was absent in neonatal ly bursectomized chickens. Moreover, cimetidine stimulated bursal cell proliferation at day 1 after sensitization. The study of the immunogl obulin class of oxazolone antibodies produced in the immunized chicken s demonstrated that cimetidine stimulated the IgM oxazolone antibody s ynthesis in Eth-OX immunized chickens and inhibited the IgY oxazolone antibody production in Eth-OX and total oxazolone antibody production in CFA-OX immunized chickens. The relationship between increased IgM o xazolone antibody synthesis and enhancement of the cutaneous Arthus re action is discussed. The role of IgM antibodies in the pathogenesis of Arthus reaction in the chicken is hypothesized. (C) 1997 Elsevier Sci ence B.V.