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

Abstract

SUMMARYWe have investigated TNF-a secretory response of peripheral blood mononuclear eells (PBMC) from 13 uraemic patients undergoing regular haemodiaiysis with cuprophane membrane (CM). Sixteen healthy subjects and five uraemic patients under conservative therapy were also studied as controls. Cells ofhacmodialy.sis patients exhibited increa.sed TNF-a release//irf/rrnn the absence of activating siimuli other than culture conditions, as compared with normal and uraemic controls. In contrast to normal cells, this spontaneous secretion of TNF-i Irom dialysis PBMC could not be significantly reduced by addition of polymyxin B to culture medium, thus indicating its mdependence of trace amount of lipopoiysaccharide (LPS) present in the medium as contaminant. Furlhcrmorc. predialysis PBMC were considerably more sensitive to stimulation with 10'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'-j release from monoeytes, PBMC were cultured on CM in vitro. Contact with CM stimulated TNF-::( secretion from PBMC above the level ofcells cultured on tis,sue culture plastic. This response persisted with time in culture in contrast to a transient LPS-induced TNF-x 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 stimulation, while a 2-day treatment ofceils with LPS was followed by LPS refractory state. Therefore, direct conuici with CM induces in PBMC a long-lasting TNF-2 response which is not down-regutated by the acquisition ofrefractorincss in a manner similar to that which occurs in the case of LPS stimulation. These in vitro findings provide a possible explanation ofthe observalion ihat predialysis PBMC exhibit elevated TNF'-a secretory capacity.