The Role of Suppressor Cells in Avian Allogeneic Tolerance: Implications for the Pathogenesis of Marek's Disease

Abstract

Chicken embryos injected with pooled spleen cells from outbred embryos are tolerant to histocompatability antigens of the donor population. Tolerance can be shown by the failure of peripheral blood cells (PBC) from tolerant birds to produce graft versus host lesions on the chorioallantoic membrane of outbred chicken embryos. It is shown that PBC from tolerant chickens can reduce by up to 85% the GVH reactivity of PBC from normal chickens. These results are interpreted to indicate that the PBC of birds tolerant to allogeneic cells contain active suppressor cells that can reduce the activity of normal cells in their response to allogeneic stimulation. The implications of these results are discussed in relation to the pathogenesis of Marek's disease—a common herpes virus-induced lymphoid neoplasm of chickens. It is suggested that resistance to neoplasia in this disease occurs because of the establishment of a population of active suppressor cells that prevents a neoplastic lymphoid proliferation.