Hemopoiesis and immune functions in dogs following fetal liver transplantation

Ten beagles were exposed to total body X-irradiation (3 X 6 Gy) and rescued with cryopreserved fetal liver cells from DLA-identical siblings obtained around the 52nd day of gestation. Grafts contained 0.2-1.6 X 10(8) mononuclear cells/kg and 0.9-19.8 X 10(4) granulocyte-macrophage progenitor cells/kg. Hemopoiesis and immune functions were followed for up to one year after fetal liver transplantation (FLT). There was a prompt engraftment in all recipients. Bone marrow metaphases were always of donor origin, whereas some host lymphocytes circulated for 2-3 months. Blood granulocytes and monocytes rose to pre-treatment levels within 2-3 weeks of FLT and platelets and erythrocytes were normal within 3-4 and 5-6 weeks, respectively. The relative incidence of bone marrow CFU-GM was normal by day 14 and the absolute numbers of circulating CFU-GM remained elevated for one year after day 14. Blood lymphocytes reached control numbers between days 35 and 101 with a faster B cell than T cell recovery. Their response to mitogen stimulation was normal by day 75, while the mixed lymphocyte reaction tended to be reduced for one year. Serum levels of IgM (day 35) and IgG (day 49) recovered earlier than IgA levels (day 270). Thus, cryopreserved canine fetal liver cells can restore hemopoiesis and immunocompetence with considerable rapidity in histocompatible, adult siblings pre-treated with total body irradiation, and, since they lack mature T cells, may be used to analyze effector mechanisms that mediate rejection of T cell-depleted allografts under less favourable conditions.