T cells activate the tumor necrosis factor-alpha system during hemodialysis, resulting in tachyphylaxis

T-cell ageing in end-stage renal disease patients: Assessment and clinical relevance

End-stage renal disease (ESRD) patients have a defective T-cell-mediated immune system which is related to excessive premature ageing of the T-cell compartment. This is likely to be caused by the uremia-associated pro-inflammatory milieu, created by loss of renal function. Therefore, ESRD patients are highly susceptible for infections, have an increased risk for virus-associated cancers, respond poorly to vaccination and have an increased risk for atherosclerotic diseases. Three ageing parameters can be used to assess an immunological T-cell age. First, thymic output can be determined by assessing the T-cell receptor excision circles-content together with CD31 expression within the naïve T cells. Second, the telomere length of T cells and third the T-cell differentiation status are also indicators of T-cell ageing. Analyses based on these parameters in ESRD patients revealed that the immunological T-cell age is increased by on average 20 years compared to the chronological age. After kidney transplantation (KTx) the aged T-cell phenotype persists although the pro-inflammatory milieu is diminished. This might be explained by epigenetic modifications at hematopoietic stem cells level. Assessment of an immunological T-cell age could be an important tool to identify KTx recipients who are at risk for allograft rejection or to prevent over-immunosuppression.

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 related to imbalanced cytokine systems, such as tumour necrosis factor (TNF)-alpha and interleukin (IL)-2. Despite activation of these systems, haemodialysis patients show high susceptibility for infections and malignancies, and have a poor immunological reaction to T-cell-dependent antigens, like hepatitis B vaccination. In this study we have determined the activation status of the two different cytokine systems, at the single cell level, using quantitative flow cytometry.

METHODS

Using fluorescein isothiocyanate- or phycoerythrin-conjugated antibodies directed against TNF-R2 (CD120b), IL-2Ralpha (CD25) and IL-2Rbeta (CD122), we measured the expression of these receptors at the single cell level in order to determine the level of activation of monocytes and T-lymphocytes.

RESULTS

Significantly higher expression of the TNF-alpha receptor, TNF-R2, was present on both monocytes and T-lymphocytes in patients on renal replacement therapy (RRT) compared with pre-dialysis chronic renal failure (CRF) patients and controls, indicating activation of the TNF-alpha system. In contrast, IL-2R expression was comparable in all groups studied, which may reflect a non-activated state of the IL-2 system.

CONCLUSIONS

The present study illustrates an activated state of the TNF-alpha system in patients on RRT, at the single cell level, while the IL-2 system seems to be unaffected. These findings support the hypothesis that the interaction between the TNF-alpha and IL-2 cytokine systems is disturbed.