ELECTRON-MICROSCOPIC OBSERVATIONS OF IMMUNOREACTIVE CELLS IN RHEUMATOID SYNOVIAL MEMBRANE

The perivascular infiltrates of the human rheumatoid synovium were examined by EM. Lymphocyte-rich, plasma cell-rich and transitional areas were observed. The transitional areas contained lymphocytes, plasma cells, blast cells, macrophages and fibroblasts. Although lymphoblasts were frequent, the blast cells were predominantly plasmablasts. Marked degeneration of fibroblasts in the vicinity of lymphoblasts suggested the liberation of a lymphotoxin by the lymphoblasts. There was close contact between blast cells and macrophages and between macrophages and lymphocytes. The close association of lymphoblasts, plasmablasts and macrophages in the transitional areas suggests that these are sites of T- [thymus-derived] and B- [bone marrow-derived] cell interaction in the rheumatoid synovial immune response.