Genetic control of resistance to Marek's disease.

Various MD-resistant and MD-susceptibel lines of chickens were challenged with the RPL-1 cell line, an MD tumor cell line which is capable of growth both in vivo and invitro. Birds which possessed the B21 allele, an allele shown to be associated with MD resistance, were also resistant to the growth of the RPL-1 tumor. Lines of chickens which possessed B alleles associated with susceptibility to MD were also very susceptible to the growth of the RPL-1 tumour. The growth of RPL-1 cells can therefore be used as a marker of B21-associated resistance to MD. In contrast, lines of chickens which differ in susceptibility to MD, due to allelic differences at a non-B genetic locus (or loci), did not differ with respect to their capacity to reject RPL-1 cells. We suggest that this might indicate that different mechanisms might be operative in B-associated versus non-B-associated resistance to MD. In addition, females were more susceptible than males to RPL-1 challenge and the RPL-1 tumour demonstrated a predilection for growth in the ovary.