Alterations in mononuclear cell tumour necrosis factor-alpha (TNF-a) response in patients on long term cuprophane haemodialysis

Abstract

SUMMARY We have investigated TNF-a secretory response of peripheral blood mononuclear cells (PBMC) from 13 uraemic patients undergoing regular haemodialysis with cuprophane membrane (CM). Sixteen healthy subjects and five uraemic patients under conservative therapy were also studied as controls. Cells of haemodialysis patients exhibited increased TNF-a release in vitro in the absence of activating stimuli other than culture conditions, as compared with normal and uraemic controls. In contrast to normal cells, this spontaneous secretion of TNF-a from dialysis PBMC could not be significantly reduced by addition of polymyxin B to culture medium, thus indicating its independence of trace amount of lipopolysaccharide (LPS) present in the medium as contaminant. Furthermore, prc-dialysis PBMC were considerably more sensitive to stimulation with It)7 pg/ml of LPS under in vitro culture conditions than normal and uraemic controls. To elucidate a role of direct contact with CM in stimulation of TNF-a release from monocytes. PBMC were cultured on CM in vitro. Contact with CM stimulated TNF-a secretion from PBMC above the level of cells cultured on tissue culture plastic. This response persisted with time in culture in contrast to a transient LPS-induccd TNF-a release. Furthermore. PBMC stimulated by contact with CM for 2 days did not lose the capacity to secrete TNF-a in response to a subsequent LPS stimululion, while a 2-day treatment of cells with LPS was followed by LPS refractory slate. Therefore, direct contact with CM induces in PBMC a long-lasting TNF-a response which is not down-regulated by the acquisition of refractoriness in a manner similar to that which occurs in the case of LPS stimulation. These in vitro findings provide a possible explanation of the observation that predialysis PBMC exhibit elevated TNF-a secretory capacity.