Epidemic polyarthritis: a cytological, virological and immunochemical study.

A patient with epidemic polyarthritis was studied within 48 hours of onset when specific serum antibodies were still low. The synovial fluid showed a fall in hyaluronic acid level and rise in protein levels though the immune globulins, and especially IgM, rose to a lesser degree and remained well below the levels in the serum. Attempts to grow virus from synovial fluid or blood lymphocytes failed despite the use of several new techniques. The complement components C'3 and C'4 were not depleted in serum or synovial fluid. The synovial fluid was devoid of neutrophil leucocytes, and contained predominantly monocytes and macrophages which were remarkable for mitotic and for enhanced and indiscriminate phagocytic activity. From this and other evidence, an explanation is proposed for the cytological response and difficulties in recovering infective virions in virus-induced arthritis. No virus antigen was detected in the supernatant synovial fluid and electron microscopy showed virus-like particles only in cytolysosomes.