CONVERSION IN-VIVO FROM AN EARLY DOMINANT TH0 TH1 RESPONSE TO A TH2 PHENOTYPE DURING THE DEVELOPMENT OF COLLAGEN-INDUCED ARTHRITIS/

Over the past decade, the central role of T cells in the process of co llagen-induced arthritis (CIA) has been extensively documented. The in flammatory features of CIA and its successful modulation after treatme nt in vivo with Th2 lymphokines, known to down-regulate proinflammator y cytokines, classify CIA as a Th1-mediated disease. However, no direc t evidence for the presence of the different T helper subsets has been obtained. To identify the collagen-specific CD4(+) T cell subset(s) d eveloping during the course of CIA, lymph nodes from susceptible DBA/1 mice (H-2(q)) were harvested at different times after injection of bo vine type II collagen in Freund's complete adjuvant and checked by enz yme-linked immunospot assay for the production of interferon (IFN)-gam ma and interleukin (IL)-4. The results clearly showed that type II col lagen-specific T cells secreting either IFN-gamma, IL-4, or both, deve lop early in vivo, before the onset of arthritis: the number of IFN-ga mma-secreting cells was already maximal 15 days after immunization, wh ereas more IL-4-secreting cells were found at day 30, just before the onset of clinical arthritis. Another strategy was to establish collage n-specific CD4(+) T cell lines and sublines in vitro and to analyze th eir lymphokine secretion pattern. Lines generated 8 days after immuniz ation displayed a mixed lymphokine secretion pattern characteristic of Th0 cells or of a mixture of Th1 and Th2 cells. After limiting diluti on of a day 8 line, 60 % of the growing sublines were Th0-like (secret ing IFN-gamma, IL-4, and IL-5), and 25 % were Th1 (secreting IFN-gamma ). By day 25 post-immunization, 33 % of the generated sublines were Th 0-like, 11 % Th1, and 56 % Th2 (secreting IL-4 and IL-5). Moreover, al l the sublines raised from the lymph nodes of arthritic mice harvested at day 55 secreted high amounts of Th2 lymphokines, and only 3 out of 14 also produced some IFN-gamma. This study demonstrates that during the course of CIA the collagen-specific CD4(+) T cell response shifts in vivo from a dominant Th0/Th1 response to a clear Th2 phenotype. The se results contribute to our understanding of the collagen-specific CD 4(+) T helper subsets which develop during the induction and clinical phases of CIA.