The influence of dialysis membranes on immunoglobulin and interleukin-6 production was estimated in vitro. Peripheral blood mononuclear cells from 11 patients undergoing hemodialysis were incubated for 7 days on Cuprophan, Hemophan, and polyacrylonitrile flat sheet membranes. IgG, IgA, IgM, and IL-6 were assayed in the supernatants with the aid of enzyme-linked immunosorbent assay (ELISA) techniques. Pokeweed mitogen-stimulated IgG production declined significantly from 319 +/- 40 ng/ml on polystyrole to 162 +/- 26 ng/ml on Cuprophan; 135 +/- 25 ng/ml on Hemophan; and 109 +/- 20 ng/ml on polyacrylonitrile. A similar pattern was observed for IgA and IgM production. IL-6 production was significantly reduced in the presence of Cuprophan (151 +/- 45 pg/ml), Hemophan (167 +/- 6 pg/ml), and polyacrylonitrile (108 +/- 33 pg/ml) when compared with polystyrole (724 +/- 34 pg/ml). It was concluded that the long-term exposure of mononuclear cells to artificial surfaces during dialysis may contribute to the impaired humoral response observed in dialysis patients. This effect may be due to a decline in B cell stimulation by monocytes, a possibility suggested by the reduction in monocytic IL-6 production.