Lymphoid leukosis in chickens chemically bursectomized and subsequently inoculated with bursa cells

Lymphoid leukosis (LL), a neoplasm of the bursa-dependent lymphoid cells of the chicken, was induced by Rous-associated virus-1 in susceptible chickens. Cyclophosphamide (CY), which destroyed the lymphoid elements of the bursa of Fabricius and abrogated humoral immunity, prevented LL. Concomitantly, osteopetorosis and other neoplasms increased. Transfer of bursa cells from chickens into CY-treated hatchmates restored immune competence. Birds whose B-cell functions were reconstituted died of LL and were less likely to die of osteopetrosis and other neoplasms than were CY-treated chicks. These results suggested that the bursa cell transferred into the CY-treated chicks were the target cells for lymphoid leukosis transformation.