Identification of a population of large granular lymphocytes obtained from the rheumatoid joint coexpressing the CD3 and CD16 antigens

In this study, we phenotypically characterized large granular lymphocytes (LGL) among the synovial fluid mononuclear cells obtained from rheumatoid arthritis (RA) patients. Cytochemical and flow cytometric studies revealed an increased percentage of LGL in the synovial fluid mononuclear cells obtained from patients with RA compared to those without RA. Flow cytometric analysis revealed an expanded population of cells expressing a rare phenotype: CD3+ CD16+. While these cells are seen in very low percentages in normal individuals (<2%) and have been reported in T cell lymphoproliferative disorders. In 20 30 RA patients studied, these cells constituted from 20 to 80% of the total synovial fluid mononuclear cells. Furthermore, studies of synovial fluids with >20% CD3+ CD16+ cells failed to show significant cytolytic activity even after incubation with recombinant interleukin-2, while fluids with <20% CD3+ CD16+ cells possessed normal cytolytic activity. Studies of matched blood and fluid in eight patients with RA demonstrated a significantly increased percentage of CD3+ CD16+ cells in synovial fluid compared to peripheral blood. Modulation and absorption studies did not provide evidence that the CD16 antigen present on these CD3 cells was due to passive adsorption of soluble CD16 antigens. Thus, while the relevance of these cells in the pathogenesis of RA is not clear, this report identifies CD3+ CD16+ cells in a disease state other than T cell lymphoproliferative disorders.