Antigens related to the major internal protein, p27, of a psoriasis associated retrovirus-like particle are expressed in patients with chronic arthritis.

A rabbit antiserum against the major internal protein, p27, of a psoriasis associated retrovirus-like particle has been applied in an immunofluorescence assay for the detection of antigens cross reacting with p27 in patients with psoriatic arthritis, seronegative rheumatoid arthritis, or ankylosing spondylitis. Antigens reacting with anti-p27 antibodies were present in lymphocytes from blood or synovial fluid from all patients examined. However, the expression was restricted to 0.01-0.1% of the cells. Among the positive p27 cells were cells reacting with markers for T, B, or NK cells. The anti-p27 antibodies also reacted with mononuclear cells in the synovial membrane and with the internal wall of some small or medium sized vessels in sections of synovial biopsy specimens from the patients with chronic arthritis. The reaction with mononuclear synovial membrane cells was restricted to approximately 0.1% of the cells. Blood lymphocytes or synovial sections from healthy persons did not react with the anti-p27 antibodies. The implication of these observations in the pathogenesis of chronic arthritis in man is discussed.