Objective: To delineate in greater detail the phenotype of T cells that reside in the synovial tissue (ST) and synovial fluid (SF) of patients with rheumatoid arthritis (RA), in order to determine their precise differentiation status, and to determine whether the accumulation of these specific T cell subsets in these synovial compartments could be related to their capacity for transendothelial migration.
Methods: Lymphocytes from normal subjects or from the peripheral blood (PB), ST, and/or SF of RA patients were phenotypically analyzed by flow cytometry. Normal PB CD4+ T cells were also characterized using an in vitro assay of transendothelial migration.
Results: ST and SF were found to be enriched with memory (CD45RA-,CD45RO+,CD11abright,CD44bright and activated (CD69+) T cells. Moreover, ST and SF cells from RA patients were enriched in differentiated CD4+,CD45RBdim,CD27- T cells, a subset of mature memory T cells that develops after prolonged antigenic stimulation. In addition, PB of some RA patients contained an increased number of CD4+,CD45RBdim,CD27- T cells. The CD4+,CD11abright,CD44bright memory T cells, which included the CD45RBdim,CD27- more mature memory cells, exhibited an enhanced capacity for transendothelial migration that is likely to contribute to their enrichment in the rheumatoid synovium.
Conclusion: RA patients manifest an increased number of mature memory T cells in the SF and ST, and some also have an increased number of these cells in PB that is likely to reflect chronic antigenic stimulation. The enrichment of these cells in the SF and ST reflects, in part, an enhanced capacity to migrate from the vascular space into inflamed tissue.