Nonspecific immunosuppression and expression of avian myeloblastosis virus (BAI strain A).

Chickens were treated with cyclophosphamide in order to induce nonspecific immunosuppression. Treated and untreated animals were injected with avian myeloblastosis virus (AMV) or myeloblasts at the age when a pronounced resistance to the disease is observed. Chickens treated with cyclophosphamide and then challenged with AMV developed acute myeloblastic leukemia in 70 percent. Similarly treated chickens transplanted with fresh AMV producing myeloblasts exhibited 30 percent incidence of myeloblastosis. In contrast, the control animals without treatment showed no myeloblastosis either after myeloblasts application or AMV injection. These results have shown that nonspecific immunosuppression by cyclophosphamide treatment strongly affects the expression of AMV in age-resistant chickens.