CD3+CD56+ natural killer T cell activity in children with different forms of juvenile idiopathic arthritis and the influence of etanercept treatment on polyarticular subgroup.

Juvenile idiopathic arthritis (JIA) has three major onset types with widely varying clinical features. We assessed the natural killer T (NKT) cell function in patients with different JIA subtypes, and found systemic patients exhibited lower NKT cell counts, perforin and granzyme B expression, while the pauciarticular and polyarticular patients displayed higher perforin and granzyme B expression as compared with the controls. The synovial fluid had more NKT cells with higher levels of perforin, granzyme B, and tumour necrosis factor (TNF)-α than peripheral cells. The polyarticular patients that responded to etanercept had lower NKT cell counts, intracellular perforin, granzyme B and the mean fluorescence intensity of TNF-α than the patients that did not respond. Treatment with etanercept reduced the granzyme B and perforin, interferon (IFN)-γ and TNF-α expression in NKT cells in the responsive group. Therefore, a higher NKT cell function may indicate a decreased response to etanercept in polyarticular patients.