Rheumatoid arthritis (RA) is characterized by chronic inflammation of the joints, followed in advanced staged by cartilage and bone destruction. The exact cellular mechanisms resulting in joint destruction have not been fully elucidated. It is likely that many cell types are involved in initiating the autoimmune reaction, and that complex interactions with synovial cells in the joint results in erosion. There is evidence for a dominant role for CD4 T cells and their cytokines in disease initiation, but definitive studies have not been carried out. This proposal will involve a systematic analysis of CD4 subsets and in particular the cytokines they secrete during RA. Mice induced to develop RA-like symptoms by immunization with collagen type II will be used as a model. CIA provides a system in which disease severity can be manipulated and CD4 responses easily monitored. The primary aim will be to assess induction of collagen- specific CD4 cells, including location, timing, and specifically the type of cytokines produced. Several cytokines, including Th1 and Th2-type, will be measured after in vitro stimulation of cells taken from collagen immunized animal, and again after effector CD4 generation. Kinetics of response following both primary and secondary immunizations will be assessed, and correlated with disease incidence and severity. Collagen specific CD4 effectors will be generated by in vitro manipulation, which exhibit Th1, Th2 and Th0 cytokines patterns. These will be adoptively transferred into SCID or AtxBM mice followed by collagen immunization to see whether disease is induced by a specific profile of cytokines. In addition, the same effectors will be transferred into normal mice that have previously been immunized with collagen, to assess whether CD4 cells secreting a particular cytokine pattern will exacerbate or suppress ongoing disease. In all cases, T cell responses will be correlated with appearance of collagen-specific antibodies in the serum. Finally, to complement to in vitro analyses of cytokines, antibodies raised for use with fixed or frozen tissue sections will be utilized to assess location of cytokine production in situ during disease, including the cell type and cell interactions involved in secretion. Altogether these studies should provide a very comprehensive picture of CD4 T cell and cytokine involvement in arthritis, and may lead to therapeutic strategies by which disease can be modulated.