Comparison of immune response potentiation and in vivo inflammatory effects of Freund's and RIBI adjuvants in mice.

Freund's adjuvant and the RIBI adjuvant system were compared for their immune potentiating and toxic effects. Each adjuvant was administered with benzo(a)pyrene (BaP), a nonimmunogenic hapten, conjugated to a bovine gamma globulin (BGG) carrier protein to 10 mice intraperitoneally. Complete Freund's adjuvant was used at initial immunization, while incomplete Freund's was used for booster immunizations. Five mice were given the immunogen conjugate (BaP-BGG) in saline as a control. Antibody titers were determined by ELISA to both hapten and carrier after each of the two booster immunizations. Titers to BaP were 2- and 27-fold higher for RIBI than for Freund's after each of two booster immunizations. Titers to bGG were 119 and 12-fold higher for RIBI compared with Freund's. Titers to both immunogens were markedly less when administered in saline. Body weights were monitored in all three groups for the duration of the study. No differences were observed among the three groups. Mice from each group were euthanized at regular intervals to assess pathology. Splenic weight:body weight ratios were determined at the time of necropsy, and no differences were noted among the three groups. Granulomatous inflammatory lesions were most severe in the Freund's immunized mice, less severe in those immunized with RIBI, and least with saline. Results indicate that the RIBI system was more effective in potentiating an immune response and elicited less tissue reaction than did Freund's adjuvant with this particular immunogen.