OBJECTIVES Assessment of the numbers and spatial distribution of cells producing interleukin 1α (IL1α), interleukin 1β (IL1β), tumour necrosis factor α (TNFα), and interleukin 6 (IL6) in the synovial membranes of patients with rheumatoid arthritis (RA).

RESULTS A wide variation between subjects was recorded for both quantities and profiles of expressed cytokines, despite similar macroscopic and histopathological features of inflammation. IL1α and IL1β were the most abundant monokines identified, though produced at different sites. IL1α was predominantly seen in vascular endothelial cells, whereas IL1β staining was mainly shown in macrophages and fibroblasts. Concordant results for the detection of TNFα at protein and mRNA levels were obtained with an unexpectedly low number of TNFα producing cells compared with IL1 expressing cells in many patients with RA. Specimens acquired arthroscopically from areas with maximum signs of macroscopic inflammation showed an increased number of TNFα producing cells in pannus tissue compared with that occurring in synovial villi of a given joint. This clustered distribution was not found for cells expressing any of the other studied cytokines.

CONCLUSION The recorded heterogeneous profile of proinflammatory cytokine synthesis in the synovial membrane among patients with RA may provide a clue for an understanding of the wide variation in responsiveness to different modes of antirheumatic treatment between patients.