DNA synthesis-potentiating activity on mouse thymocytes of synovial fluid of rheumatoid arthritis patients

DNA synthesis-potentiating activity in synovial fluids of rheumatoid arthritis (RA) patients was studied in vitro by using phytohemagglutinin-stimulated mouse thymocytes. The activity was present only in fluids obtained during the active RA phase, and no activity was noted in fluids obtained during the inactive RA phase or in fluids of osteoarthritis deformans patients.