MAREK'S disease virus (MDV) of chickens induces lymphomas and other lymphoproliferative changes, which, depending on the virulence of the strain used, may terminate in paralysis and death. Chickens genetically selected for resistance, however, are refractory to clinical MD and most chickens that are fully susceptible when young develop resistance as they become older. Resistance acquired with age is expressed through lesion regression1,2. Our studies with genetic and age resistance established that humoral immunity did not play a major role in either type of resistance3,4 and now we present evidence that the thymus-dependent immune system is of principal importance in the natural resistance of old chickens.
ASJC Scopus subject areas