IL-1 secreting cell assay and its application to cells from patients with rheumatoid arthritis.

The cells within a population that were secreting interleukin-1 (IL-1) were enumerated and visualized by an ELISA-SPOT assay. Initial experiments designed to validate the assay revealed that the number of IL-1 beta spot forming cells was increased by exposing normal blood monocytes to LPS and that spot formation was prevented by incubating the cells with cycloheximide. Normal blood polymorphonuclear leucocytes (PMNs) produced IL-1 alpha and IL-1 beta in response to recombinant granulocyte monocyte colony stimulating factor (rhGMCSF) but not to cytochalasin B, calcium ionophore or LPS. Monocytes and PMN were isolated from the synovial fluid (SF) and blood of patients with rheumatoid arthritis (RA) and the ability of these cells to secrete IL-1 alpha and IL-1 beta compared. A higher proportion of SF derived monocytes were found to secrete IL-1 beta spontaneously compared to the corresponding blood cells. IL-1 alpha secreting monocytes were not detected although high numbers of IL-1 alpha secreting cells were found among cells isolated from rheumatoid synovium. By contrast SF PMNs did not produce IL-1 alpha or IL-1 beta whereas blood PMNs from some (3/8) RA patients produced IL-1 alpha and/or IL-1 beta. It is considered that the IL-1 ELISA-SPOT is a highly sensitive technique for detecting IL-1 secreting cells.