Effect of infectious bovine rhinotracheitis virus infection on bovine alveolar macrophage function

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Abstract
Bovine alveolar macrophages isolated in culture were assessed for immunological activity in assays for Fc and complement receptors, for phagocytosis, and for effector cell function in antibody-dependent cell cytotoxicity. In the case of uninfected alveolar macrophages, Fc receptors were detected on approximately 94% of macrophages and complement receptors were detected on 39%. Phagocytosis of immunoglobulin G-coated sheep erythrocytes occurred in 58% of macrophages, and phagocytosis of opsonized Candida parapsilosis, mediated by the complement receptor, was observed in 68% of cells. Alveolar macrophages were efficient effector cells in antibody-dependent cell cytotoxicity. Infection of macrophages with infectious bovine rhinotracheitis (IBR) virus resulted in reductions in Fc-mediated receptor activity and phagocytosis after approximately 12 and 6 h, respectively. Complement receptor activity was initially elevated and then markedly reduced. Macrophages retrieved from IBR-immune and -susceptible donors were affected to a similar extent. The ability of macrophages to participate in antibody-dependent cell cytotoxicity was reduced dramatically from 2 h after IBR virus infection, suggesting that IBR virus-infected alveolar macrophages undergo alterations in immunological activity long before morphological changes in the cells become apparent.