The Role of Lipid in the Induction of Hapten-Specific Delayed Hypersensitivity and Contact Sensitivity

Abstract

Guinea pigs immunized with bovine serum albumin conjugated with dinitrophenol (BSA-DNP), in Freund's complete adjuvant, produce antibody to the DNP and delayed-type hypersensitivity (DTH) to the BSA. We report that immunization with BSA-DNP doubly conjugated with medium chain fatty acids (L-BSA-DNP) stimulates the production of DTH specific for the hapten DNP with minimal antibody to DNP and no detectable immune response to the carrier BSA. The production of hapten-specific DTH reactions was assessed by two methods. First, animals immunized with L-BSA-DNP produced typical contact sensitivity reactions to epidermal challenge with dinitrofluorobenzene. Second, they produced grossly and microscopically typical delayed hypersensitivity reactions to the intradermal injection of DNP conjugated either to BSA or to a non-cross-reacting carrier, hen egg albumin. In further experiments, DNP-specific DTH was produced by animals immunized with BSA-DNP to which lipid groups had been attached by electrostatic rather than covalent bonds. Evidence is discussed which indicates that the production of DTH to haptens and proteins is largely a function of the lipophilic nature of the entire immunogen and is not dependent upon properties of individual antigenic determinants. Autoradiographic studies with ¹²⁵I-labeled material demonstrated that the lipid-rich antigens are localized in the paracortical area of lymph nodes, in close proximity to the thymus-derived cells which are stimulated in the induction of DTH.