Objective To examine the expression of FLICE-inhibitory protein (FLIP) in juvenile idiopathic arthritis (JIA) and analyze its correlation with synovial inflammation. Methods The expression of FLIP was assessed in 11 JIA and 3 normal synovial tissue samples by reverse transcription-polymerase chain reaction (RT-PCR) and immunohistochemistry. The cell types expressing FLIP were further characterized

and the correlation of FLIP expression with the degree of synovial inflammation

as well as the activity of caspase 8 was then analyzed. Results RT-PCR revealed the expression of FLIP mRNA in all 11 JIA samples

but not in 3 normal synovial tissues. In JIA

FLIP expression could be found in both the lining and sublining layers

mainly in the macrophage-like cells. Moreover

the expression of FLIP in JIA synovial tissues was positively correlated with the degree of synovial inflammation (r=0.563

P<0.05). Conclusion The expression of antiapoptotic FLIP in JIA synovial tissue and its correlation to accumulation of inflammatory cells in synovial tissue suggests that FLIP potentially extends the lifespan of synovial cells and thus contributes to the progression of joint destruction.