The preventive effects of incomplete Freund's adjuvant and other vehicles on the development of adjuvant-induced arthritis in Lewis rats

The present study showed a novel finding that the development of adjuvant-i nduced arthritis (AA) in Lewis rats was completely prevented by incomplete Freund's adjuvant (IFA) injected 21 or 28 days before complete Freund's adj uvant (CFA) challenge. Hexadecane also completely prevented AA and squalane , methyl oleate and pristane moderately prevented PLA, though pristane by i tself induced mild arthritis in two out of five rats. Concanavalin A-stimul ated lymph node cells (LNCs) isolated from AA rats were able to adoptively transfer the severe polyarthritis to all the naive recipients or even to th e IFA pretreated recipients with earlier onset and more rapid progression t han those of AA. The LNCs from the donors who had been pretreated with IFA and subsequently challenged with CFA could induce mild arthritis in only tw o out of eight naive recipients, whereas all the recipients who were challe nged with CFA immediately after intravenous injection of these LNCs develop ed significantly less severe arthritis. However, the LNCs from IFA-pretreat ed donors failed to prevent AA. According to the T helper type 1 (Thl)/Th2 paradigm, it was suggested that the adjuvant-active vehicles such as IFA, h exadecane, squalane, methyl oleate and pristane, can affect and deviate the Thl/Th2 balance of immune responses in host. CFA could promote the propaga tion of Th2 cells rather than Thl cells in these vehicle-pretreated rats th rough as yet undetermined mechanisms, eventually resulting in the preventio n of AA. Finally, we discussed a regulatory role of adjuvant vehicles for i nduction and suppression of AA.