The 65-kDa mycobacterial heat shock protein (Bhsp65) has been invoked in the pathogenesis of both adjuvant arthritis (AA) in the Lewis rat (RT.1l) and human rheumatoid arthritis. Arthritic Lewis rats in the late phase of AA show diversification of the T cell response to Bhsp65 C-terminal determinants (BCTD), and pretreatment of naive Lewis rats with a mixture of peptides representing these neoepitopes affords protection against AA. However, the fine specificity and physiologic significance of the BCTD-directed T cell repertoire, and the role of homologous self (rat) hsp65 (Rhsp65), if any, in spreading of the T cell response to Bhsp65 have not yet been examined. We observed that T cells primed by peptides comprising BCTD can adoptively transfer protection against AA to the recipient Lewis rats. However, these T cells can be activated by preprocessed (peptide) form of BCTD, but not native Bhsp65, showing that BCTD are cryptic epitopes. The BCTD-reactive T cells can be activated by the naturally generated (dominant) C-terminal epitopes of both exogenous and endogenous Rhsp65 and vice versa. Furthermore, certain individual peptides constituting BCTD and their self homologs can also induce protection against AA. These results support a model for the diversification of T cell response to Bhsp65 during the course of AA involving up-regulation of the display of cryptic BCTD coupled with spontaneous induction of T cell response to the cross-reactive dominant C-terminal epitopes of Rhsp65. The identification of disease-regulating cryptic determinants in Ags implicated in arthritis provides a novel approach for immunotherapy of rheumatoid arthritis.

Green tea, a product of the dried leaves of Camellia sinensis, is the most widely consumed beverage in the world. The polyphenolic compounds from green tea (PGT) possess anti- inflammatory properties. We investigated whether PGT can afford protection against autoimmune arthritis, and also examined the immunological basis of this effect using the rat adjuvant arthritis (AA) model of human rheumatoid arthritis (RA). AA can be induced in the Lewis rat (RT.1l) by immunization with heat-killed Mycobacterium tuberculosis H37Ra (Mtb), and arthritic rats raise T cell response to the mycobacterial heat-shock protein 65 (Bhsp65). PGT (2-12 g/L, w/v) was fed to rats in drinking water for 1-3 wk followed by disease induction by Mtb injection. Thereafter, these rats were observed regularly and graded for signs of arthritis. Sub-groups of these rats were killed at defined time points, and their draining lymph node cells (LNC) were harvested and tested for T cell proliferative and cytokine responses. Furthermore, the sera collected from these rats were tested for anti-Bhsp65 antibodies. We observed that feeding 8 g/L PGT to Lewis rats for 9 d significantly reduced the severity of arthritis compared to the water-fed controls. Interestingly, PGT-fed rats had lower concentrations of the pro-inflammatory cytokine interleukin-17 (IL-17), but greater concentration of the immunoregulatory cytokine IL-10 than controls. PGT feeding also suppressed the anti-Bhsp65 antibody response. Thus, green tea induced changes in arthritis related immune response. We suggest further systematic exploration of dietary supplementation with PGT as an adjunct nutritional strategy for the management of RA.

Many autoimmune diseases are believed to involve primarily T cell-mediated effector mechanisms. There is increasing realization, however, that Abs may also play a vital role in the propagation of T cell-driven disorders. In this study, on the rat adjuvant-induced arthritis (AA) model of human rheumatoid arthritis, we examined the characteristics of serum Ab response to mycobacterial heat shock protein (hsp) 65 (Bhsp65), self (rat) hsp65 (Rhsp65), and linear peptides spanning these two molecules. The AA-resistant WKY (RT.1l) rat responded to the heat-killed Mycobacterium tuberculosis immunization with a rapid burst of Abs to both Bhsp65 and Rhsp65. These Abs reacted with numerous peptide epitopes; however, this response was reduced to a few epitopes with time. On the contrary, the susceptible Lewis (RT.1l) rat developed a relatively lower Ab response to Bhsp65, and Abs to Rhsp65 did not appear until the recovery from the disease. The Ab response in Lewis rats diversified with progression of AA, and there was an intriguing overlap between the repertoire of Bhsp65-reactive B and T cells during the recovery phase of AA. Nonetheless, subsets of the repertoire of the late Abs in both rat strains became focused on the same epitope regions of Bhsp65 and Rhsp65. The functional relevance of these Abs was evident from the results showing that sera from recovery phase Lewis or WKY rats, but not that of naive rats, afforded protection against subsequent AA. These results are of significance in further understanding of the role of humoral immunity in the pathogenesis of autoimmune arthritis.

Conclusion. These results provide the first evidence that lymphopenia-associated homeostatic proliferation of autoreactive CD4؉ T cells potentiates autoimmune arthritis, and that inhibition of this process protects mice from the development of this pathologic condition.

HSP90 is one of the most abundant heat shock proteins (HSPs) in eukaryotic cells and is found in complex with several regulatory proteins such as kinases and transcription factors. Geldanamycin (GA), a benzoquinone ansamycin, specifically binds to HSP90 and disrupts the interaction of HSP90 and target proteins. Thus, GA has been used as a specific inhibitor of HSP90. In this study, we examined whether GA could affect protein synthesis and gene expression in the human erythroleukemic cell line K562. Treatment with GA, but not herbimycin A (another benzoquinone ansamycin), highly induced a 70-kDa protein, which was revealed to be HSP70 by immunoblotting and immunoprecipitation with anti-HSP70 antibody. The expression of HSP28 was also enhanced by GA. Furthermore, GA induced the activation of heat shock factor 1 (HSF1), but not HSF2, as determined by electromobility shift and electromobility supershift assay. In addition, similar to heat shock treatment, GA induced the phosphorylation of HSF1. Heat shock element-binding activity and phosphorylation of HSF1 were attenuated 3 h after GA treatment. These results indicate that the functional inactivation of HSP90 by GA potentially stimulates the expression of heat shock proteins through activation of HSF1.