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Adjuvanticity of dimethyl dioctadecyl ammonium bromide in guinea pigs. I. Skin test reactions.

The effect of the adjuvant dimethyl dioctadecyl ammonium bromide (DDA) on the induction of cellular immunity in guinea pigs was studied. DDA, a surface-active lipid, was mixed with the antigen bovine serum albumin (BSA) or with a conjugate of BSA and dinitrophenol (DNP22--BSA) and injected into the footpads of guinea pigs. At varying intervals skin tests were performed to test the immediate and delayed hypersensitivity (DH) reactions. Optimal DH reactions to BSA were observed from 3 to 6 weeks after immunization with BSA in DDA. The hapten-specific response to DNP22--BSA had an optimum at 3 weeks and was highly specific for the homologous antigen. Histological examinations of skin test sites confirmed that the reaction was rather of the tuberculin type than of the cutaneous basophil hypersensitivity type. When guinea pigs were immunized with DNP22--BSA in Freund's complete adjuvant (FCA) a long-lasting DH to both carrier and hapten groups developed but the DH was always complicated by an Arthus reaction due to antibodies to the DNP hapten. In conclusion, DDA is superior to FCA as adjuvant for the induction of a state of pure DH in guinea pigs.