Effect of antithymocyte serum on collagen arthritis in rats: evidence that T cells are involved in its pathogenesis.

To assess the role of T cells in collagen arthritis, a heterologous T cell-specific antiserum (ATS) was administered intraperitoneally to female Wistar-Furth rats. ATS treatment on Day -1, 1, 3, and 5 and immunization with native chick type II collagen on Day 0 resulted in a decreased incidence of arthritis (5 of 19, 26%) compared to immunized rats given either nonimmune heterologous serum on these days (20 of 25, 80%) or ATS injected on Day 5, 7, 9, and 11 (17 of 20, 85%) (P less than 0.001 for both comparisons). The early-ATS protocol also was associated with a delayed onset and reduced disease severity in the few rats in this group that did develop arthritis. Both delayed-type hypersensitivity (DTH) and serum IgG antibody titers to native type II collagen, measured on Day 10, were decreased significantly (P less than 0.002) in rats administered ATS beginning on Day -1 compared to the other two groups. These data suggest that T cells contribute to the inception of collagen arthritis and that their critical function occurs within the first 5 days after immunization.