Conversion in vivo from an early dominant Th0/Th1 response to a Th2 phenotype during the development of collagen‐induced arthritis

Abstract

Over the past decade, the central role of T cells in the process of collagen‐induced arthritis (CIA) has been extensively documented. The inflammatory features of CIA and its successful modulation after treatment in vivo with Th2 lymphokines, known to down‐regulate proinflammatory cytokines, classify CIA as a Th1‐mediated disease. However, no direct evidence for the presence of the different T helper subsets has been obtained. To identify the collagen‐specific CD4⁺ T cell subset(s) developing during the course of CIA, lymph nodes from susceptible DBA/1 mice (H‐2q) were harvested at different times after injection of bovine type II collagen in Freund's complete adjuvant and checked by enzyme‐linked immunospot assay for the production of interferon (IFN)‐γ and interleukin (IL)‐4. The results clearly showed that type II collagen‐specific T cells secreting either IFN‐γ, IL‐4, or both, develop early in vivo, before the onset of arthritis: the number of IFN‐γ‐secreting cells was already maximal 15 days after immunization, whereas more IL‐4‐secreting cells were found at day 30, just before the onset of clinical arthritis. Another strategy was to establish collagen‐specific CD4⁺ T cell lines and sublines in vitro and to analyze their lymphokine secretion pattern. Lines generated 8 days after immunization displayed a mixed lymphokine secretion pattern characteristic of Th0 cells or of a mixture of Th1 and Th2 cells. After limiting dilution of a day 8 line, 60% of the growing sublines were Th0‐like (secreting IFN‐γ, IL‐4, and IL‐5), and 25% were Th1 (secreting IFN‐γ). By day 25 post‐immunization, 33% of the generated sublines were Th0‐like, 11% Th1, and 56% Th2 (secreting IL‐4 and IL‐5). Moreover, all 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‐γ. 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. These results contribute to our understanding of the collagen‐specific CD4⁺ T helper subsets which develop during the induction and clinical phases of CIA.