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.
Copyright 2000 S. Karger AG, Basel