RT Journal Article SR Electronic T1 CD4+ PD-1+ T cells accumulate as unique anergic cells in rheumatoid arthritis synovial fluid. JF The Journal of Rheumatology JO J Rheumatol FD The Journal of Rheumatology SP 1410 OP 1419 VO 30 IS 7 A1 Saori Hatachi A1 Yoshiko Iwai A1 Seiji Kawano A1 Sahoko Morinobu A1 Masaya Kobayashi A1 Masahiro Koshiba A1 Ryuichi Saura A1 Masahiro Kurosaka A1 Tasuku Honjo A1 Shunichi Kumagai YR 2003 UL http://www.jrheum.org/content/30/7/1410.abstract AB OBJECTIVE: The PD-1 receptor, whose deficiency in mice causes autoimmune diseases such as arthritis, is considered to be a negative regulator of activated T cells and to play a crucial role in peripheral tolerance. To clarify the involvement of the PD-1 system in rheumatoid arthritis (RA), we investigated PD-1 expression on synovial fluid (SF) T cells from patients with RA. METHODS: FACS analysis for PD-1 was performed on SF T cells from 44 patients with RA and 6 with osteoarthritis (OA), and also on peripheral blood (PB) T cells from 12 RA patients and 7 healthy controls. Two-color analysis of cell surface PD-1 expression and the intracellular concentration of cytokine production was used to investigate CD4+ T cells from SF of patients with RA and PB from controls. RESULTS: Scarcely any PD-1 expression was detected on control PB T or OA SF T cells. In contrast, PD-1+ cells made up 20.9 +/- 8.6% (mean +/- SD) of RA SF T cells. In RA SF, PD-1 was expressed more predominantly on CD4+ T cells than on CD8+ T cells. As well as expressing CD45RO and CXCR3, CD4+ PD-1+ T cells were mostly CTLA-4 positive and CD26 negative, and were enriched in CD45RB(low) cells. Intracellular cytokine staining revealed that CD4+ PD-1+, but not CD4+ PD-1-, T cells produced interleukin 10 (IL-10), and that CD4+ PD-1+ T cells produced less IL-2 than CD4+ PD-1- T cells. CONCLUSION: PD-1+ T cells in RA SF are enriched, and phenotypic analysis suggests that these cells constitute a unique anergic T cell subset in RA SF.