Arthritis in Lewis rats induced by the non-immunogenic adjuvant CP20961: an immunohistochemical analysis of the developing disease.

OBJECTIVES--The role of lymphocytes and macrophages in developing adjuvant arthritis induced by an injection of CP20961 in inbred Lewis rats was studied over a 32 day period using a novel biotin-avidin immunoperoxidase histochemical technique. METHODS--Fresh frozen sections of hind paws and spleens, as well as lymph nodes draining the site of the injected adjuvant were immunostained using a panel of monoclonal antibodies specific for subsets of lymphocytes and macrophages and for MHC Class II antigen. RESULTS--An increase in the numbers of activated T-lymphocytes was detected early in the draining lymph nodes before hind paw swelling had begun. The presence of these cells in significant numbers was only observed in the vicinity of the joint after joint swelling and damage had begun. Macrophages were among the first cells to invade the swollen paws and later were found with T-lymphocytes and cells bearing the MHC class II antigen at the face of eroding and re-organising bone. CONCLUSIONS--The activity of T-lymphocytes in initiating arthritis appeared to occur early in lymph nodes. Joint destruction was more closely associated with the arrival of macrophages but later arrival of T-lymphocytes may have contributed to the maintenance of chronic inflammation.