Since interleukin-7 (IL-7) has been shown to induce monocyte production of IL-1, IL-6, IL-8, and tumor necrosis factor-alpha, we investigated plasma and synovial fluid levels of IL-7 in patients with juvenile rheumatoid arthritis (JRA).
IL-7 levels were measured using an ELISA in 60 patients with JRA and in 25 patients with other rheumatic disorders (ORD).
In patients with systemic JRA, but not in patients with polyarticular or pauciarticular JRA or with ORD, plasma IL-7 levels were significantly higher (p < 0.0001) than those of healthy controls. IL-7 was undetected in all synovial fluid tested. Among patients with systemic JRA, those with persistent systemic symptoms had IL-7 levels significantly higher (p < 0.01) than those of patients in which systemic symptoms subsided.
Plasma IL-7 levels are elevated in patients with systemic JRA and are associated with the presence and severity of systemic symptoms.