Ex vivo apoptosis, CD95 and CD28 expression in T cells of children with juvenile idiopathic arthritis.

We hypothesise that T-cell apoptosis and the percentage of T cells expressing molecules involved in apoptosis modulation (CD95, CD28) are altered at the inflammation site and in peripheral blood (PB) of children with juvenile idiopathic arthritis (JIA). Paired JIA samples of synovial fluid (SF) and PB ( n=7) and PB samples from age-matched normal children ( n=23) were analysed immediately ex vivo. Apoptosis was measured by detection of phophatidylserine (PS) externalisation on T cells. CD95 or CD28 was detected by FACS, and soluble CD95 and CD95 ligand levels were detected by enzyme-linked immunosorbent assay (ELISA). In SF, the mean percentage of apoptotic T cells was somewhat higher than in PB. However, the percentages of T cells expressing CD95 and soluble CD95 levels were markedly higher in SF (CD4 cells 96+/-2%, CD8 91+/-6%, soluble CD95 6,420+/-2,571 pg/ml) than in PB (CD4 32+/-10%, CD8 36+/-9%, soluble CD95 4,296+/-2,142 pg/ml). Peripheral blood T-cell apoptosis in JIA (CD4 20+/-8%, CD8 42+/-19%) was higher than in the control group (CD4 5+/-2%, CD8 9+/-6%). Interestingly, the percentage of PB CD4 cells expressing CD28 was lower in JIA than controls. In conclusion, systemic T-cell apoptosis was higher in JIA while a substantial number of SF T cells survived locally, despite the fact that almost all cells express CD95.