To investigate the function of Fas ligand (Fas-L) positive T cells in rheumatoid synovium, we analyzed the T cell receptor (TCR) CDR3 region and examined the expression of cytokines in both Fas-L+ and Fas-L- single T cells.
Synovial fluid (SF) samples were collected from 2 patients with rheumatoid 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, interleukin 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 region was sequenced.
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 amino 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 motif 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 cells, 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.
Fas-L+ TCR BV8+ T cells revealed the conserved amino acids motif in the CDR3 region, suggesting that Fas-L+ T cells might expand by antigen stimulation and play a crucial role as Th0-type T cells in triggering autoimmunity in rheumatoid synovium.