Ontogeny and line differences in the mitogenic response of chicken lymphocytes

Ontogeny of mitogen response was studied using Regional Poultry Research Laboratory lines 6 and 7 and Cornell lines JM-N and -P chickens over a 30-week experimental period. Purified lymphocyte assay and sequential monitoring with whole-blood assay show lines 6 and N to be low responders compared to lines 7 and P, respectively. The difference in phytohemagglutinin (PHA) response between lines 6 and 7 increased with age, whereas that between lines N and P remained consistent for all ages. An association seems to exist between the low PHA responsiveness of lines 6 and N and resistance to Marek's disease (MD), a lymphoproliferative disease caused by MD virus in susceptible chickens. The fact that lines 6 and 7 have the same B2-haplotype but differ in PHA response seems to substantiate the evidence by others that the genetic control of PHA response is not linked to the Ea-B locus of the MHC complex. This does not preclude, however, the possibility that the response of lines N and P is MHC-linked.