Interleukin 1 in rheumatoid arthritis: potentiation of immune responses within the joint.

Specific immunoassays were used to measure IL-1 peptides in the serum and synovial fluid of patients with rheumatoid arthritis (RA) and in the serum of age-matched healthy controls. Patients with RA had raised levels of both IL-1 beta and IL-1 alpha in their sera compared to controls. Synovial fluid levels of IL-1 beta significantly correlated with immunoreactive IL-2 and soluble IL-2 receptor (sIL-2R). In addition, incubation of synovial fluid MNC with human recombinant (hr) IL-1 caused a dose-dependent increase in the level of sIL-2R in the cell supernatant. Finally, production of IL-1 beta and IL-6 from RA peripheral blood (PB) and synovial fluid (SF) MNC was examined. PBMNC spontaneously produced low levels of IL-1 beta and IL-6 that were augmented by the addition of hr IL-1 alpha. In contrast, SFMNC spontaneously produced high levels of IL-1 beta but only low levels of IL-6, again this production was augmented by the addition of hr IL-1 alpha. Taken together, the data suggests that IL-1 potentiates immune responses within the joint.