Dual CD45RA, CD45RO positive T-lymphocytes within rheumatoid arthritic joints.

This report documents the presence of an expanded population of dual CD45RA, CD45RO positive T cells (up to 91% of T cells) in the rheumatoid joint. Cells from peripheral blood (PB) and synovial fluid (SF) were analysed by dual immunofluorescence labelling. Synovium from a separate patient population was analysed by single and dual immunoenzyme staining of serial sections. Dual CD45RA, CD45RO positive T cells were found in PB (up to 74%), SF (up to 91%) and synovium. This was associated with a lack of early activation antigens (4F2, interleukin-2 receptor, transferrin receptor) but increased HLA-Class II antigens (HLA-DR, -DP, -DQ) in SF compared with PB. This intermediate activation phenotype may support the hypothesis that T cell activation or reactivation occurs within the rheumatoid joint.