TNC and juvenile idiopathic arthritis: In contrast, the evaluation of the effect of etanercept therapy on tenascin C blood concentration in children with JIA over successive periods of administration showed that TNC concentration significantly increased only after 24 months of therapy (p < 0.05) compared to tenascin C levels observed in both untreated children and those undergoing 3-, 6-, 12-, and 18-month therapy, as illustrated in Figure 1c.