Expression of viral antigens after infection of human lymphocytes, monocytes, and macrophages with influenza virus.

Previous studies demonstrated that in vitro infection with influenza A viruses altered several functions of human monocytes and macrophages, but did not detectably alter functions of human lymphocytes. For a determination of whether both types of leukocytes can be infected by the influenza viruses, human mononuclear leukocytes were infected in vitro and assayed for newly produced and cell surface-expressed viral antigens, with use of indirect immunofluorescence techniques and flow cytometry. Infected cells, including both monocytes and lymphocytes, expressed viral hemagglutinin, neuraminidase, and matrix protein on their surfaces. The expression of influenza virus antigens by such immunocompetent cells may be important in human antiviral defense.