T-cell function, T-cell phenotype and its role in responsiveness to recombinant human erythropoietin in hemodialysis patients.

Resistance to recombinant human erythropoietin (Epo) occurs in a small proportion of hemodialysis (HD) patients. In this study we investigated the relationship between T-cell phenotype (using flow cytometry), T-cell function (by measuring in vitro cytokine production) and responsiveness to Epo in HD patients and to compare the results with those from healthy controls. T-cell phenotypes were assessed and T-cell function was studied. The study included 24 chronic renal failure (CRF) patients on HD treated with rHuEPO as well as 14 normal control subjects. Dual-colour immunofluorescence and flow cytometry were used to compare the surface antigen expression on freshly isolated CD4+ and CD8+ T-cells from PBMC of the studied groups. Levels of a panel of selected cytokines (IL-4, IFN-gamma, slL-2R and IL-10) were determined in PBMC culture supernatants and in plasma samples (TNF-alpha, IFN-gamma, IL-6, slL-2R) using (ELISA) kits. Patients were followed-up for 24 months and a survival study was carried out. T-cells from poor responders showed increased proportions of CD4+/CD28- cells and CD8+/CD28- cells compared with both good responders and controls. Compared with their CD28+ counterparts, CD4+/CD28- T-cells produced significantly more IFN-gamma, enabling them to function as pro-inflammatory cells. There was no difference in secretion of IFN-gamma, slL-2R or IL-4 in PBMC cultures obtained from HD patients and controls. However, Unstimulated PBMC from poor responders generated increased levels of IL-10 poor compared with both good responders and controls. Plasma slL-2R and IL-6 were significantly elevated in both good and poor responders compared with controls. Plasma levels of IFN-gamma and TNF-alpha were undetectable in both HD patients and controls. In the follow up period, more deaths were occurring among the poor responders than the good responders. Based on the finding of the this study we may suggest that, in the absence of any obvious cause, poor response to Epo may be mediated by generation of cytokines from a subpopulation of activated T-cells, which might promote apoptosis in erythroid progenitor cells in the bone marrow.