Quantitative flow cytometry shows activation of the TNF-alpha system but not of the IL-2 system at the single cell level in renal replacement therapy

Background. Immunological dysfunction in patients on haemodialysis may be r elated to imbalanced cytokine systems. such as tumour necrosis factor (TNF) -alpha and interleukin (IL)-2. Despite activation of these systems, haemodi alysis patients show high susceptibility for infections and malignancies, a nd have a poor immunological reaction to T-cell-dependent antigens, like he patitis B vaccination. In this study we have determined the activation stat us of the two different cytokine systems, at the single cell level, using q uantitative flow cytometry. Methods, Using fluorescein isothiocyanate- or phycoerythrin-conjugated anti bodies directed against TNF-R2 (CD120b), IL-2R alpha (CD25) and IL-2R beta (CD122), we measured the expression of these receptors at the single cell l evel in order to determine the level of activation of monocytes and T-lymph ocytes. Results. Significantly higher expression of the TNF-alpha receptor. TNF-R2, was present on both monocytes and T-lymphocytes in patients on renal repla cement therapy (RRT) compared with pre-dialysis chronic renal failure (CRF) patients and controls, indicating activation of the TNF-alpha system. In c ontrast, IL-2R expression was comparable in all groups studied, which may r eflect a non-activated state of the IL-2 system. Conclusions. The present study illustrates an activated state of the TNF-al pha system in patients on RRT. at the single cell level, while the IL-2 sys tem seems to be unaffected. These findings support the hypothesis that the interaction between the TNF-alpha and IL-2 cytokine systems is disturbed.