Dimethyl diotadecyl ammonium bromide as adjuvant for delayed hypersensitivity in mice.

Immunization of mice with antigen mixed with cationic surface active lipid dimethyl dioctadecyl ammonium bromide (DDA) produced delayed type hypersensitivity (DH), measured as a footpad swelling. The DH to sheep red blood cells or dinitrophenyl conjugated with bovine serum albumin (DNP28-BSA) in DDA exceeded the response of the same antigens in Freund's Complete Adjuvant (FCA) significantly. Treatment of mice with CY 8 hr prior to the injection of antigen in FCA or DDA resulted in delay of the onset of footpad swelling past day 5 and in elimination of the differences in the response due to the adjuvants. Immunization with carrier or hapten-carrier complexes with different epitope density in DDA and elicitation with the homologous and heterologous antigens revealed that the DH was DNP-specific. In vivo priming with DNP28-BSA in DDA and in vitro stimulation with the same antigen resulted in peak responses which were twice as high and were reached almost twice as fast as the earlier found response following immunization in FCA. The advantages of DDA as adjuvant over covalently linked fatty acid chains and over FCA are discussed.