Effect of oil composition on both adjuvant-induced arthritis and delayed hypersensitivity to purified protein derivative and peptidoglycans in various rat strains.

We confirmed that, when immunized with a conventional complete Freund adjuvant (water in oil), Lewis rats were highly susceptible to adjuvant arthritis, Fisher rats were less susceptible, and Buffalo rats were much less susceptible. However, mycobacterial delipidated cells in squalane (squalane-type adjuvant) produced severe arthritis with almost 100% incidence even in the less susceptible rat strains except for Buffalo rats. With regard to an immune response, Freund complete adjuvant induced strong delayed hypersensitivity to purified protein derivative (PPD) and peptidoglycan (PG) in all rat strains used, Whereas the squalane-type adjuvant induced these hypersensitivities only in Lewis and Buffalo rats, but not in Fisher and Brown Norway rats. No correlation was found between development of arthritis and delayed hypersensitivity to either PPD or PG, or both. It seems that PPD hypersensitivity may be inherited differently from PG hypersensitivity.