Inhibitory effects of macrophages against Marek's disease virus plaque formation in chicken kidney cell cultures.

Inhibition of plaque formation by Marek's disease virus (MDV) in chicken kidney cell cultures was investigated with the use of peritoneal exudate cells (PEC) from chickens. PEC from MDV-infected White Leghorn chickens inhibited the formation of MDV plaques, whereas the inhibitory effect of PEC from chickens vaccinated with herpesvirus of turkey (HVT) or PEC from normal chickens was very weak. However, PEC from either normal chickens or HVT-vaccinated chickens inhibited the MDV plaque formation in the presence of serum from MDV-infected chickens but not from normal or HVT-vaccinated chickens. The capacity of PEC to inhibit plaque formation was significantly reduced when PEC was treated with carrageenan but not with antithymus or antibursa cell serum. These results indicate that macrophages may have a role in protection against Marek's disease by reducing the number of MDV-infected cells and thereby decreasing the spread of the virus in vivo.