Immunomodulatory effects of secondary hyperparathyroidism on circulating CD4+ and CD8+ T-lymphocytes in chronic renal failure patients.

The immunomodulatory effects of parathyroid hormone (PTH) in patients with end stage renal disease (ESRD) is controversial. This study was carried out to investigate the effect of PTH levels on the circulating CD4+, CD8+ T cell counts (%) in patients with chronic renal failure (CRF) on regular hemodialysis ((HD). The study included 22 patients with serum levels of PTH < 300 pg/ml (group 1), 18 patients with PTH > 300 pg/ml (group II) and 10 age and sex matched normal controls (group III). Chemiluminescence and flowcytometry assays were performed for determination of serum PTH levels and T cell subset counts respectively. The mean (%) of total lymphocyte, CD4+, CD8+ and CD4\CD8 ratio of group I were (81.68+/- 9.38), (52.00+/-6.24), (27.13+/- 6.31) and (1.99+/-0.42) respectively, as compared to (73.83+/-13.30), (46.05+/-8.59), (23.05+/-4.63) and (2.03+/-0.41) respectively in group II. Values of group I and II were significantly (P<0.001) lower than controls (88.50 +/- 6.02), (63.30 +/- 6.44), (36.80 +/- 6.44) and (1.76+/-0.36) respectively. In group II, the reduction was significantly (P<0.001) prominent in patients with high PTH levels, with significant inverse correlations (P<0.001) between PTH and % of total lymphocyte (r= -0.93), CD4+ (r= -0.74) and CD8+ % (r=-0.69). In conclusion, increased level of PTH in CRF patients on hemodialysis is associated with lymphopenia and reduction in CD4+ & CD8+ subsets of T cells. Monitoring circulating PTH levels in such patients can restore their immune competence.