Calcitriol therapy modulates the cellular immune responses in hemodialysis patients

We studied the in vitro and in vivo effects of calcitriol (1,25D) on the cellular immune responses in 19 hemodialysis (HD) patients. In vitro 5-day treatment with 1,25D markedly reduced the HLA-DR expression by peripheral blood CD14(+) monocytes from both HD patients and normal subjects in a similar fashion. The HLA-DR expression by monocytes and the phorbol myristate acetate (PMA)-induced superoxide production (SOP) by neutrophils were significantly higher in the HD patients than in the normal subjects (p < 0.01 and p < 0.05, respectively). The phagocytic activity in the HD patients was significantly lower than that in the normal subjects (p < 0.05). Moreover, the mitogen response of HD peripheral blood lymphocytes against pokeweed mitogen (PWM) was significantly lower than that of the controls (p < 0.01) but was only slightly and insignificantly lower against Con A. Oral 1,25D pulse therapy resulted in a marked decrease in the HLA-DR expression by peripheral blood monocytes 2 and 4 days after the first 1,25D administration (p < 0.01) in HD patients. Moreover, the treatment significantly enhanced the PMA-induced SOP 2 days after the treatment (p < 0.01). However, the phagocytic activity by neutrophils and the mitogen responses to Con A and PWM by lymphocytes were not significantly affected by this treatment. These results suggest that 1,25D plays a significant role in the regulation of both the monocyte and neutrophil functions in HD patients.