Human cytomegalovirus induces an Fc gamma receptor (Fc gammaR) in endothelial cells and fibroblasts that is distinct from the human cellular Fc gammaRs.

The expression of a trypsin-sensitive receptor for the Fc portion of IgG (Fc gammaR) was demonstrated by flow cytometry on the surface of human umbilical vein endothelial cells and fibroblasts infected with human cytomegalovirus (CMV). Double-labeling experiments showed strong expression of the CMV Fc gammaR in a perinuclear region of infected cells but not in bystander uninfected cells. The CMV Fc gammaR did not react with a panel of murine monoclonal antibodies directed against the known human IgG Fc receptors, Fc gammaRI, Fc gammaRII, and Fc gammaRIII. The cytoplasmic form but not the cell surface form of CMV Fc gammaR bound murine IgG3 moderately and murine IgG1 more weakly, while both forms bound rabbit IgG almost as strongly as human IgG. The function of CMV Fc gammaR is unclear, but it may allow CMV to evade host antibody responses. However, the binding of immune complexes to infected endothelium might also contribute to immunopathology.