Comparative studies on effects of incomplete oil adjuvants with different physical properties

The author investigated the effects of Freund's incomplete adjuvant (FIA) with different physical properties on precipitin formation and skin hyperreactivity in rabbits and mice following intramuscular injection of ovalbumin (OA) with the adjuvant. Histopathological changes in the injection site and in some visceral organs were also examined. The observation periods after the injection for mice and rabbits were 20 and 28 weeks, respectively. In contrast to the most reports, FIA of both imperfectly emulsified-water-in-oil (W/O II) and oil-in-water (O/W) types were sometimes equivalent or superior to perfectly emulsified water-in-oil (W/O 1) type FIA in the enhancing effects in precipitin formation both in rabbits and mice. The skin displayed the immediate type hypersensitivity reaction to OA throughout the observation period irrespective of the type of adjuvant. The O/W type often caused significantly stronger skin hyperreactivity than the other types. Histopathological findings in the injection site indicated that the abscess formation in rabbits was severer than that in mice, and that the O/W type induced the severest abscess. No relation was found between free fatty/acid contents of adjuvant emulsion and abscess formation in either animal species. Granuloma formation in mice was always severer than that in rabbits. The O/W type caused extremely weak granuloma in mice, and none in rabbits. Histopathological changes in main visceral organs, being dependent on the emulsion type, were also discussed.