Background: Patients on chronic intermittent haemodialysis (HD) show an impaired cellular and humoral immune response that clinically appears with frequent infectious complications and low vaccination responses. This immune defect strongly correlates with reduced in vitro proliferative responses of T cells. The defect is localized in antigen presenting cells, which show a decreased co-stimulatory activity. Furthermore, the impaired immune response correlates with an increased production of pro-inflammatory cytokines. In response to primary activation, CD4 positive T helper (Th) cells mainly differentiate into either Th1 or Th2 cells. Th1 cells support cell mediated immunity whereas Th2 cells enhance humoral immune responses. Since both types of responses mutually inhibit each other, the impaired humoral immune response seen in HD patients could either be due to a reduced number of Th2 cells or to a predominant Th1 response.
Methods: We analysed the Th cell profile in HD patients using flow cytometry. Monocytic cytokine expression was analysed using both flow cytometry and enzyme linked immunoadsorbant assays.
Results: Our data demonstrate that the cytokine differentiation profile in circulating T cells from HD patients is dysregulated and characterized by an increase in Th1 cells, but a normal amount of Th2 cells. Moreover, the skewed helper cell responses correlate with a higher percentage of monocytes capable of secreting the Th1 promoting cytokine interleukin 12 (IL-12).
Conclusions: Our findings contribute to a better understanding of the pathogenesis of impaired cellular immune functions in dialysis patients and, in particular, the decreased antibody production after vaccination. They provide a link between overproduction of pro-inflammatory cytokines (IL-12) and imbalanced T-cell activation.