Albumin density gradient purification of canine hemopoietic blood stem cells (HBSC): long-term allogeneic engraftment without GVH-reaction.

Long-term repopulation of the blood-forming organs of dogs, conditioned by wholebody X-irradiation (1200 R midplane dose), was achieved by transfusion of cryopreserved allogeneic blood mononuclear cells (MNC) without causing graft-versus-host-reaction (GVH-R). Donor and recipient dogs were DL-A identical, MLC-negative, no siblings, non-related. The blood stem cells (CFUc) were procured by a 3- to 4-hour continuous-flow leukapheresis. To increase the CFUc concentration in the peripheral blood, dextran sulfate (DS) was administered intravenously beforehand. About 1 x 10(10) MNC, among them about 1 x 10(7) CFUc, were collected and further segregated using a discontinuous albumin density gradient. Less dense cells were to be found in the upper part of the gradient (fraction 2). These cells included most of the CFUc, enriched by a factor of between 275 and 1730 compared to their concentration in the peripheral blood beforehand. After cryopreservation, these cells, when transfused into lethally irradiated dogs, completely repopulated the marrow and lymph nodes, caused no GVH-R and allowed long-term survival. These dogs received no immunosuppressive therapy, either before or after transfusion. More dense MNC were to be found in fraction 3; their transfusion caused a severe GVH-R, followed quickly by death. Fraction 4 was rich in lymphocytes and poor in CFUc. The transfusion of these cells produced a selective plasma-cell hyperplasia of the lymph nodes but failed to repopulate permanently the marrow. The reappearance of the different cell lineages in the marrow and in the peripheral blood after conditioning and transfusion of these cells produced a selective plasma-cell hyperplasia of the lymph nodes but failed to repopulate permanently the marrow. The reappearance of the different cell lineages in the marrow and in the peripheral blood after conditioning and transfusion of the segregated MNC is described in detail.