Interferon system in patients with systemic juvenile chronic arthritis: in vivo and in vitro studies.

Eighteen patients with active systemic juvenile chronic arthritis (JCA) were studied for periods of up to 1 year to see whether any relationships existed between the interferon (IFN) response, the course of the underlying disease and intercurrent infections. The control group consisted of 23 children who were each seen on one occasion. IFN-alpha production by mononuclear cells (MNC) cultured in vitro was stimulated with Newcastle disease virus (NDV). Comparison of the mean IFN-alpha responses from all patients with control responses showed that MNC from the JCA group produced significantly more IFN-alpha. Furthermore, MNC obtained from JCA patients at times of systemic flare produced significantly higher titres of IFN-alpha than at times when the patients were clinically stable. IFN-alpha production by MNC from individual patients fluctuated considerably from occasion to occasion whereas IFN-gamma production by MNC induced with phytohaemagglutinin (PHA) remained more stable. There was no significant difference between patients and controls with respect to IFN-gamma responses and no relationship with clinical condition. Serum IFN was not detected either by sensitive bioassays for IFN-alpha and IFN-gamma or by an immunoradiometric assay for IFN-alpha.