In vivo cimetidine immunomodulatory effects on the cutaneous reaction to oxazolone in the chicken

The effect of the histamine H2-receptor antagonist, cimetidine, on the cutaneous Arthus-like hypersensitivity to oxazolone elicited injecting subcutaneously oxazolone conjugated to egg-albumin (EA-OX) has been examined in the chicken. Cimetidine had opposite effects on the cutaneous reaction to oxazolone in relation to a different immunization schedule. Cimetidine enhanced the cutaneous reaction to oxazolone obtained immunizing chickens with oxazolone dissolved in ethanol (Eth-OX); instead cimetidine inhibited the cutaneous reaction obtained in chickens immunized with oxazolone dissolved in complete Freund adjuvant (CFA-OX). Optimum enhancement of the cutaneous arthus-like reaction to oxazolone occurred when cimetidine was given for three consecutive days starting at the immunization. The enhancing effect was absent in neonatally bursectomized chickens. Moreover, cimetidine stimulated bursal cell proliferation at day 1 after sensitization. The study of the immunoglobulin class of oxazolone antibodies produced in the immunized chickens demonstrated that cimetidine stimulated the IgM oxazolone antibody synthesis 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 oxazolone antibody synthesis and enhancement of the cutaneous Arthus reaction is discussed. The role of IgM antibodies in the pathogenesis of Arthus reaction in the chicken is hypothesized.