A phagocytic challenge with IgG-coated erythrocytes depresses macrophage respiratory burst and phagocytic function by different mechanisms

A phagocytic challenge with IgG-coated erythrocytes (EIgG) previously has b een shown to cause impaired macrophage respiratory burst capacity and Fc ga mma R-mediated phagocytic function. Because both the respiratory burst and Fc gamma R-mediated phagocytosis are dependent on the release of arachidona te (AA), we evaluated the effects of impaired AA release on the depression of macrophage function caused by a phagocytic challenge. Challenge with EIg G caused a depression of A23187-stimulated AA release that was associated w ith impaired phorbol myristate acetate (PMA)stimulated H2O2 production and Fc gamma R-mediated phagocytic function. In contrast, challenge with IgG-co ated glass beads (BIgG) had no effect on either AA release or H2O2 producti on but did depress phagocytic function. Exogenous AA prevented the depressi on of H2O2 production but had no effect on phagocytic function. Phospholipa se A(2) (PLA(2)) activity was depressed under conditions where AA release w as impaired. The depression of phagocytic function was correlated with a de pression of both EIgG binding and Fc gamma R expression. Thus, a phagocytic challenge with EIgG results in macrophage dysfunction by depressing PLA(2) activity and depleting Fc gamma R.