The distribution of dendritic cells in the synovial fluids of patients with arthritis.

We have investigated the cellular composition of 108 consecutive samples of synovial fluid from patients with Juvenile Chronic Arthritis (JCA), Rheumatoid Arthritis (RA) and Osteoarthritis (OA). Particular emphasis was placed upon the enumeration of cells with dendritic morphology and the study of their in vitro function. Whilst the cellularity of the synovial fluids varied by a factor of greater than 100 within patient groups, the fluids obtained from patients with inflammatory arthritis (JCA & RA) were more cellular than those from patients with non-inflammatory arthritis (OA). This was also noted with respect to both the number and proportion of dendritic cells. The dendritic cells stimulated allogeneic mixed leucocyte reactions, and enhanced mitogenic responses of peripheral blood lymphocytes when present in numbers as low as 1% of the total mononuclear cells. Syngeneic stimulation of blood lymphocytes by similar numbers of dendritic cells was usually negative. However, occasionally there was a marked syngeneic stimulation, which may be evidence for the presentation of antigen by dendritic cells within the arthritic joint.