Human Immunologic Response to Soluble Antigens

Abstract

Abstract Volunteers were injected intradermally and subcutaneously with soluble dinitrophenyl-human serum albumin (DNP-HSA) conjugates. Some responded with increasing titers of mercaptoethanol-sensitive agglutinating antibody to DNP-coupled red cells and some developed immediate type wheal and flare skin reactivity. Serum from one of these subjects was capable of passive transfer of DNP-specific wheal and flare reactions. Thirty-eight of the 55 subjects developed delayed type skin reactions to DNP-HSA. These tended to be maximal in intensity at 24 hr after testing and declined or disappeared by 48 hr in contrast to classic delayed type reactions such as those to tuberculin which are usually prominent at 48 hr. There were also differences in both gross and histologic appearance between DNP-HSA and tuberculin reactions. The response of peripheral leukocytes to antigen in vitro measured by increased DNA synthesis was considerably less to DNP-HSA than it was to tuberculin in individuals who displayed skin reactivity to both. Passive transfer of delayed reactivity to DNP-HSA with dialysates of peripheral leukocytes from sensitive individuals could not be accomplished. In contrast to the characteristic persistence of delayed sensitivity to tuberculin or other microbial antigens, delayed hypersensitivity to DNP-HSA developed early in the course of sensitization and then declined markedly in intensity or disappeared entirely with time and repeated testing. We suggest that this is a general characteristic of the human immune response to the administration of soluble antigens. This may be a distinct form of immunologic response that can be separated from both the serum antibody response and the classic delayed hypersensitivity that is induced by microbial infections or by administration of antigens in complete Freund's adjuvant.