Introduction: Immunization with glucose-6-phosphate isomerase (GPI) induces severe arthritis in DBA/1 mice. The present study was designed to identify the cytokines and co-stimulatory molecules involved in the development of GPI-induced arthritis.
Methods: Arthritis was induced in DBA/1 mice with 300 microg human recombinant GPI. CD4+ T cells and antigen-presenting cells from splenocytes of arthritic mice were cultured in the presence of GPI. Tumor necrosis factor (TNF)-alpha, IFN-gamma, IL-2, IL-4, IL-5, IL-6, IL-10, and IL-12 levels were assessed using cytometric bead array. Monoclonal antibodies to TNF-alpha, IFN-gamma, IL-12, CD40L, inducible co-stimulator (ICOS), and cytotoxic T-lymphocyte antigen 4 immunoglobulin (CTLA-4Ig) were used to block TNF-alpha and IFN-gamma production, examine clinical index in mice with GPI-induced arthritis, and determine anti-GPI antibody production.
Results: Large amounts of TNF-alpha and IFN-gamma and small amounts of IL-2 and IL-6 were produced by splenocytes from mice with GPI-induced arthritis. Anti-TNF-alpha mAbs and CTLA-4Ig suppressed TNF-alpha production, whereas anti-IFN-gamma mAbs, anti-IL-12 mAbs, and CTLA-4 Ig inhibited IFN-gamma production. A single injection of anti-TNF-alpha and anti-IL-6 mAbs and two injections of CTLA-4Ig reduced the severity of arthritis in mice, whereas injections of anti-IFN-gamma and anti-IL-12 mAbs tended to exacerbate arthritis. Therapeutic efficacy tended to correlate with reduction in anti-GPI antibodies.
Conclusion: TNF-alpha and IL-6 play an important role in GPI-induced arthritis, whereas IFN-gamma appears to function as a regulator of arthritis. Because the therapeutic effects of the tested molecules used in this study are similar to those in patients with rheumatoid arthritis, GPI-induced arthritis appears to be a suitable tool with which to examine the effect of various therapies on rheumatoid arthritis.