1α,25 Dihydroxyvitamin D 3 and Mononuclear Phagocytes: Enhancement of Mouse Macrophage and Human Monocyte Hydrogen Peroxide Production Without Alteration of Tumor Cytolysis

1α,25 dihydroxyvitamin D 3 (1,25 D 3 ) is known to interact with hematopoietic cells. The purpose of this study was to determine the effect of 1,25 D 3 on hydrogen peroxide (H 2 O 2 ) production and tumor cell killing by mouse peritoneal macrophages and human blood monocytes. Enhanced monocyte and macrophage phorbol myristate acetate (PMA)‐stimulated H 2 O 2 production was observed at concentrations of 0.13 to 130 nM 1,25 D 3 and and was maximal at 1.3 nM. At concentrations of 100 U/ml, gamma interferon (IFN‐γ) alone had a similar effect but, in combination with 1,25 D 3 , there was no cooperative effect. At concentrations ranging from 0.13 to 130 nM, 1,25 D 3 failed to augment tumor cell lysis by macrophages from peptone‐injected normal or bacillus Calmette‐Guerin (BCG)‐infected mice, or by blood monocytes from normal humans. Our results indicate that 1,25 D 3 can activate the monocyte and macrophage for H 2 O 2 secretion without concomitant activation for tumor cell killing.