Atypical T cells in rheumatoid synovial membranes.

Atypical mononuclear cells (AMC) with Sézary-cell-like morphology were demonstrated to be present in rheumatoid synovial membranes. These cells have exclusively T cell membrane characteristics, like identical cells previously found in rheumatoid synovival fluids. AMC were predominantly present in transitional areas between nodular lymphocytic aggregates and plasma cell rich areas. In ultrathin sections AMC accounted for approximately 30% of all lymphocyte cells; in studies of cells isolated from rheumatoid synovial membranes AMC comprised 30--40% of the E-rosette-forming cells. The hypothesis that these cells represent reactive T cells is discussed.