Sustained T-cell responses to collagen type II in B6 mice with collagen-induced arthritis. Inguinal lymph node cells were cultured from naïve mice or mice with early (up to 2 weeks after onset) or late (6 to 8 weeks after onset) arthritis (n = 8). Cells were cultured for 72 hours with bovine, chicken, and murine collagen type II. (a) Proliferation was assessed by 3H thymidine incorporation. (b) Interferon-gamma (IFN-γ) secretion was assessed in the culture supernatant by enzyme-linked immunosorbent assay. (c) Proliferative responses of T cells from collagen-immunised B6 mice to type II collagen purified with or without pepsin were compared. Responses to chicken collagen and anti-CD3 monoclonal antibody were also measured. Proliferation was assessed by 3H thymidine incorporation. ***P < 0.001. N.S., not significant.