Journal of Autoimmunity (2001) 17, 289–295 doi:10.1006/jaut.2001.0552, available online at http://www.idealibrary.com on Balance of Th1/Th2 Cytokines Associated with the Preventive Effect of Incomplete Freund’s Adjuvant on the Development of Adjuvant Arthritis in LEW Rats Aslam Hossain, Cong Long Zheng, Akiko Kukita and Osamu Kohashi Department of Microbiology, Saga Medical School, 5-1-1 Nabeshima, Saga 849-8501, Japan Received 11 May 2001 Accepted 13 September 2001 Key words: AA, cytokine, IFA, rats, Th1/Th2 Complete Freund’s adjuvant (CFA) could induce adjuvant arthritis (AA) in LEW rats and incomplete Freund’s adjuvant (IFA) could induce oil induced arthritis (OIA) in DA but not in LEW rats. Lymph node cells (LNCs) from these AA and OIA rats showed increased mRNA expression of IFN-, IL-2 and TNF- but not IL-4. LNCs from IFA immunized LEW rats showed increased expression of IL-4, reduced expression of IFN- and TNF- and no IL-2, in contrast to IFA immunized DA rats. The pretreatment of IFA before CFA challenge could completely prevent AA in LEW rats and their LNCs showed increased expression of IL-4 and IFN- but not IL-2 and TNF-. In F1 (LEW×DA) rats, IFA could not induce OIA but the pretreatment of IFA before CFA challenge could induce very mild AA with 80% incidence, LNCs showing an elevated expression of all the above cytokines. These findings suggest that increased Th1 cytokine expression is associated with disease development and that increased IL-4 expression or the balance of Th2 over Th1 cytokine expression plays an important regulatory role in disease development. © 2001 Academic Press Introduction Adjuvant arthritis (AA) in LEW rats is commonly used as an animal model of rheumatoid arthritis (RA). AA can be induced in LEW rats by a single intra- dermal injection of complete Freund’s adjuvant (CFA) consisting of heat-killed Mycobacterium tuberculosis (Mt) and incomplete Freund’s adjuvant (IFA) [1]. On the other hand, an intradermal injection of IFA alone can induce oil induced arthritis (OIA) in DA rats but not in LEW rats [2]. Since AA and OIA can be passively transferred to either naive or irradiated recipients by the lymph node cells (LNCs) derived from the arthritis rats, it is believed that both AA and OIA are T cell-mediated diseases [3, 4]. CD4 + T cells have been classified into two major types, T helper type 1 (Th1) and Th2 type on the basis of their distinct pattern of cytokine profiles. Th1 cells produce predominantly IFN- and IL-2, whereas Th2 cells produce predominantly IL-4, IL-5, IL-10 and IL-13 [5]. In experimental animal models of arthritis, Th1 phenotype and/or other pro-inflammatory cytokines are considered to be responsible for disease progression, while Th2 type cytokines are associated with disease resolution [6–13]. Generally, the balance of the cytokines produced by these two subsets of T cells plays a very important role in the induction and propagation of diseases. The mRNA expression of several cytokines during the various phases of AA indicated that the increased expression of Th1 and inflammatory cytokines were associated with disease progression, while the subsiding of the diseases was paralleled by increased Th2-like cytokines [9]. Alter- natively, some drugs could completely prevent or suppress the development of AA by inhibiting the production of Th1 type cytokines and inflammatory cytokines, suggesting the importance of Th1 type and inflammatory cytokines in AA [14, 15]. Furthermore, anti-inflammatory cytokine therapy (such as anti- TNF- and anti-IL-1) can also suppress the develop- ment of AA in rats [16]. The systemic administration of murine IL-4 or intra-articular inoculation of IL-4 gene can prevent the development of AA in rats, suggesting that Th2 type cytokines are important in disease resolution [17, 18]. As for AA, Th1 type and inflammatory cytokines also play an important role in the pathogenesis of OIA [12, 13]. We reported earlier that pretreatment with IFA 28 days before CFA challenge could completely prevent the development of AA in LEW rats and suggested the possible regulatory role of Th2 cells in Th1 mediated AA [19]. In order to understand the role of Th1 and Th2 cytokines in the induction or prevention of AA Correspondence to: Professor Osamu Kohashi, MD, Ph.D., Depart- ment of Microbiology, Saga Medical School, 5-1-1 Nabeshima, Saga 849-8501, Japan. Fax: (+) 81 952 342015; E-mail: kohashi@post.saga-med.ac.jp 289 0896–8411/01/080289+07 $35.00/0 © 2001 Academic Press