Mechanisms of decreased antibody-dependent cytotoxicity mediated by monocytes and neutrophils in atopic dermatitis

Abstract

By using IgG-sensitized erythrocytes as target cells, we found the antibody-dependent cytotoxicity mediated by monocytes and neutrophils to be depressed in atopic dermatitis. This change was accompanied by a reduction of phagocytosis of target cells by the effector cells, and also by a decreased lysozyme liberation from, and hexose monophosphate shunt activation in, the effector cells during the cytotoxic reaction. However, the binding of target cells to effector cells remained normal. In individual patients, cytotoxicity and phagocytosis were equally depressed. No relation was found between cytotoxicity and lysozyme liberation in atopic dermatitis, but a relation between cytotoxicity and hexose monophosphate shunt activity was highly significant. These results suggest that the decreased cytotoxicity mediated by monocytes and neutrophils in atopic dermatitis is caused by a diminished production of oxygen radicals during the respiratory burst. This reduced respiratory burst was not due to any defect in the enzymes responsible for this process, since the superoxide production of monocytes and neutrophils stimulated with phorbol myristate acetate was found normal in atopic dermatitis. It therefore seems that although binding of target cells to effector cells was normal, the signals created by the binding process were defective in activating monocytes and neutrophils in atopic dermatitis.