Effect of neonatal thymectomy on pathogenesis of herpesvirus of turkeys in chickens.

Effect of immunosuppression on pathogenicity of herpesvirus of turkeys (HVT) in chickens was studied. In three experiments, newly hatched chickens of two genetic strains were surgically thymectmized and gamma-irradiated and then exposed to HVT. Lymphoid cells of thymectomized-irradiated chickens had reduced in vitro mitogenic response; this result indicated that the immunosuppressive regimen caused suppression of T cell function. The immunosuppressed chickens had more circulating HVT and had a slightly higher frequency of microsocpic lesions in peripheral nerves than the intact control chickens, although the intensity of lymphoproliferation remained very mild and no gross lesions or clinical disease was noted during the 5-week observation period. The absence of significant lesion development in an immunosuppressed host indicated that pathogenic potentials of HVT may be limited.