IMMUNOHISTOCHEMICAL DETECTION OF LYMPHOCYTE SUBPOPULATIONS IN THE TARSAL JOINTS OF CHICKENS WITH EXPERIMENTAL VIRAL ARTHRITIS

We characterized the lymphocytes in the tarsal joint synovium of chick ens inoculated with an arthrotropic strain of avian reovirus. Cryostat sections of whole joints taken from 2 days to 35 days postinoculation were analyzed using monoclonal antibodies directed against B lymphocy tes, T lymphocytes, and chicken Ia antigen. Plasma cells were morpholo gically identified using stained sections of whole joints. Time-depend ent changes were found in the type and number of positively staining c ells. Synoviocytes and cells with a dendritic morphology stained posit ive for Ia in normal joint sections. T cells, mostly CD8 positive, wer e present in low numbers in acute phase arthritis (2-6 days postinfect ion) in the perivascular and superficial regions of the synovium. Suba cute arthritis (8-14 days postinfection) was characterized by increase d numbers of CD4 and CD8 T cells in the perivascular and superficial r egions. The perivascular T cells began to organize into aggregates, wi th IgM-positive B cells and plasma cells on the periphery of these agg regates. Some CD8-positive cells were detected on the surface of the a rticular cartilage. Cells staining positively for Ia were not lymphocy tes. Chronic arthritis (> 14 days postinfection) was characterized by large numbers of T cells in the perivascular and superficial regions, with the CD4-positive T cells found primarly in the lymphoid aggregate s of the perivascular regions. IgM-positive B cells were fewer, but mo re plasma cells, few of which stained positive for IgM, were present. Lymphocytes in chronic arthritis stained positively for Ia. These data suggest that the types, numbers, and activation level of lymphocytes present in the tarsal joints are similar but not identical to those se en in rheumatoid arthritis.