Characteristics of mononuclear cell populations in chronically inflamed synovial membranes

Mononuclear cells infiltrating synovial membranes in chronic synovitis were characterised both in situ and in cell suspensions by surface markers and histochemical techniques. T-lymphocytes were the predominant infiltrating cell in rheumatoid arthritis as well as in other forms of chronic arthritis, including ankylosing spondylitis and arthritis associated with Crohn's disease. B-lymphocytes were found exclusively in rheumatoid synovial membranes. These cells were demonstrable both in true germinal centres and, focally and diffusely, in nodular mononuclear infiltrates lacking the histochemical characteristics of germinal centres. The synovial lining cells, unlike mononuclear phagocytes, had no demonstrable receptors for C3 and Fc.