No effect of serum parathyroid hormone level on antigen presenting cell-dependent T-cell reactivity in hemodialysis patients

Abstract

Sir, Both clinical and experimental evidence, like impaired response to vaccination with T-celldependent antigens [1] or T-cell proliferation after stimulation with staphylococcal enterotoxin B (SEB) [2], suggest a defective T-cell immune response in hemodialysis patients. The contribution of parathyroid hormone (PTH) levels in this situation is not fully clarified. Some investigators showed that in patients with high serum intact PTH (iPTH), T-cell proliferation after stimulation with the T-cell receptor (TCR) dependent phytohemagglutinin (PHA) is increased in comparison with T-cells derived from patients with low iPTH levels [3]. Others proposed that chronic T-cell exposure to PTH could be responsible for altered T-cell proliferation after stimulation with mitogens [4] due to interference with cellular calcium kinetics. In order to evaluate the role of serum PTH level on T-cell reactivity in hemodialysis patients we used SEB as stimulator, since it provokes Tcell stimulation not only in a TCR-dependent, but also in an antigen presenting cell-dependent manner by cross-linking the major histocompatibility complex class II (MHCII) molecules with the TCR [5]. Consequently, SEB imitates conventional peptide antigens better than PHA and other mitogens. Moreover, in contrast with conventional peptide antigens, SEB stimulates a large proportion of T-cells [6, 7], a crucial feature for obtaining reliable results from the usual cell cultures. A total of 25 hemodialysis patients were enrolled into the study. Besides end-stage renal disease, none of them suffered by conditions like active infection, cancer, autoimmune disease or diabetes mellitus, or received medications like corticosteroids, non-steroid antinflammatory drugs, cytotoxic drugs, statins, vitamin D or calcium channel blockers that are known to alter the immune response. In total, 20 age and sex matched healthy individuals served as a control group. An informed consent was obtained from all subjects enrolled into the study. In hemodialysis patients, blood samples were drawn just before the onset of the second dialysis T. Eleftheriadis (&) AE V. Liakopoulos AE G. Antoniadi AE A. Poultsidi AE I. Stefanidis Department of Nephrology, University Hospital of Larissa, Papakiriazi 22, PC 41222 Larissa, Greece e-mail: elefthe@otenet.gr