Appearance of different lymphoid cells in synovial tissue and in peripheral blood during the course of collagen II-induced arthritis in rats.

The involvement of different sets of lymphoid cells in the development of collagen II-induced arthritis in rats was studied by means of immunohistochemical analyses on frozen sections of tissue from joint biopsy specimens taken at different phases of arthritis development. Particular attention was paid to cells involved in early pannus formation. Accumulation of anti-Ia-reactive cells close to the cartilage surface was seen early in the development of pannus, and the anti-Ia reactive cells could in later phases be seen infiltrating cartilage and crowding bone surfaces at sites of marginal erosion. With the help of monoclonal anti-T-cell subset antibodies and rabbit anti-rat immunoglobulin antiserum, it was demonstrated that synovial infiltration of T lymphocytes, particularly W3/25-reactive T "helper" cells, occurs very early in the development of arthritis, whereas a moderate increase of Ox 8-positive 'suppressor/cytotoxic' T cells and a small number of B cells and plasma cells are seen later in the course of the disease. Levels of Ia-expressing cells and of T cells belonging to different subsets were recorded in peripheral blood by means of immunocytochemical analyses on cell smears; no significant deviations from normal levels were seen during the development of arthritis.