A single cell analysis of Fas ligand positive T cells in rheumatoid synovial fluid

Objective. To investigate the function of Fas ligand (Fas-L) positive T cel ls in rheumatoid synovium, we analyzed the T cell receptor (TCR) CDR3 regio n and examined the expression of cytokines in both Fas-L+ and Fas-L- single T cells. Methods. Synovial fluid (SF) samples were collected from 2 patients with rh eumatoid arthritis. TCR BV8+ T cells were sorted into a 96 well plate at a density of one cell per well. Expression of Fas-L, interferon-gamma, interl eukin 2 (IL-2), IL-4, IL-6, and IL-10 was analyzed by reverse transcription -polymerase chain reaction and Southern blot and the TCR BV8 junctional reg ion was sequenced. Results, Twenty-two of 30 TCR BV8+ T cells from Patient 1 and 20 of 43 TCR BV8+ T cells from Patient 2 were Fas-L+ T cells, while the others were Fas- L-. Junctional sequence analysis showed the presence of some conserved amin o acid motifs in the CDR3 region (SRQ, GFG, SSG, SGS, LGTSGTL, TLSS) in 13 clones of Fas-L+ T cells from Patient 1, whereas no conserved amino acid mo tif in Fas-L- T cells was found. In Patient 2, conserved amino acid motifs (PGQ, GQG, TTWGA) in the CDR3 region were found in 6 clones of Fas-L+ T cel ls, while only one was found in 2 clones of Fas-L- cells. In Fas-L+ T cells , 90-93% expressed both IL-2 and IL-10 mRNA. Conclusion. Fas-L+ TCR BV8+ T cells revealed the conserved amino acids moti f in the CDR3 region, suggesting that Fas-L+ T cells might expand by antige n stimulation and play a crucial role as Th0-type T cells in triggering aut oimmunity in rheumatoid synovium.