The role of the macrophage in Marek's disease: In vitro and in vivo studies

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Abstract
Macrophages from Sand K-strain Leghorn chickens, susceptible and resistant to Marek's disease (MD) respectively, were studied to determine the macrophage contribution to the dynamics of MD infection, tumorigenesis and genetic resistance to this disease. In vitro studies demonstrated that macrophages from both strains were similar in their responses toward JM strain of Marek's disease virus (MDV) and JM-1 tumor cells. Macrophages were observed to phagocytize JM virus, but the interiorized virus was not seen to replicate within the macrophage or induce antigenic changes of the cell membrane. Clearance of JM-1 tumor cells was by both cytolytic and phagocytic mechanisms. In vivo selective suppression of macrophage functions by antimacrophage serum or trypan blue inoculations resulted in significantly elevated viral titers and increased tumorigenesis, as compared to infected, non-suppressed or non-infected control groups. Results from this study indicate that genetic susceptibility or resistance to MD, as exhibited by Sand K-strain chickens, respectively, is not controlled at the macrophage level. The role of the macrophage in MD infection appears to be specifically surveillance.