This is consistent with the fact that IL-10 plays a dual role in infectious diseases [37] and is in agreement with the observation made recently by Abdul-Careem [22] who recorded that the expression of the IL-10 gene followed the pattern of expression of the IFN-γ gene to a certain extent in both pre- and post-hatched herpesvirus of turkey (HVT)-immunized chickens. Here, IFNG is linked to infectious disease.