Desensitization of delayed-type hypersensitivity by antigen and specific antibody.

The role of antibody in the desensitization of delayed-type hypersnsitivity (DTH) to dinitrophenylated bovine gammaglobulin (DNP-BGG) was studied in rats. Rats sensitized by a subcutaneous injection of DNP₃₂-BGG in Freund's complete adjuvant (FCA) were desensitized 14 days later with various doses of DNP₃₂-BGG injected intravenously. It was found that only certain doses (100–500 μg) of DNP-BGG effectively desensitized, antigen doses outside this optimum range being ineffective in suppressing DTH. In adoptive cell transfer experiments, it was shown that sensitized peritoneal cells incubated with optimum doses of the antigen in the presence of specific antiserum in vitro failed to transfer the delayed response to normal recipients, whereas the treatment of the sensitized cells with the antigen or with the antiserum separately did not impair the ability of these cells to transfer DTH. The effect of desensitization is specific and is not permanent. The DTH reappears 3–4 wk after desensitizing injection.