The comparative selectivity of adjuvants for humoral and cell-mediated immunity. I. Effect on the antibody response to bovine serum albumin and sheep red blood cells of Freund's incomplete and complete adjuvants, alhydrogel, Corynebacterium parvum, Bordetella pertussis, muramyl dipeptide and saponin.

A comparison was made of seven recognized adjuvants, Freund's incomplete and complete, alhydrogel, Corynebacterium parvum, Bordetella pertussis, muramyl dipeptide and saponin, administered with BSA or SRBC by the S.C. route of immunization. Strong selectivity as well as differences in potency were revealed in relation to these two antigens. Only FIA, FCA, alhydrogel and MDP promoted the primary response to 50 microgram of BSA, and FIA was significantly superior to FCA. Immunological memory to a low dose (0.5 microgram) of BSA, which did not evoke a primary response with any adjuvant, was potentiated by alhydrogel and by MDP and, relatively poorly, by FIA. Radioimmunoelectrophoresis showed that potentiation of the response with MDP was confined to IgG1, whereas alhydrogel, FIA and FCA stimulated both IgG1 and IgG2. Saponin was outstandingly the best adjuvant for both primary and secondary haemagglutinin responses to SRBC. Of the others, alhydrogel for the primary, and alhydrogel and B. pertussis for the secondary were active to a lesser degree. The results show that the relative potency of adjuvants differs markedly according to the antigen used, and suggest that saponin may be a particularly effective adjuvant for antigens in cell membranes.