Abstract
Macrophages from Sand Kβstrain 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 JMβ1 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 JMβ1 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, nonβsuppressed or nonβinfected control groups. Results from this study indicate that genetic susceptibility or resistance to MD, as exhibited by Sand Kβstrain chickens, respectively, is not controlled at the macrophage level. The role of the macrophage in MD infection appears to be specifically surveillance.