Depletion of alloreactive donor T cells using immunomagnetic cell selection

Abstract

Donor T cells support both engraftment and immune reconstitution after allogeneic BMT. Moreover, they may exert potent anti-tumor effects (graft-versus-leukemia, GVL), which are used for adoptive immunotherapy. On the other hand, infusion of allogeneic T cells is frequently associated with the manifestation of immune reactions against healthy tissue, which may lead to life-threatening graft-versus-host disease (GVHD). To overcome this problem, we developed a new strategy for the exclusive depletion of alloreactive cells from donor leukocytes. We activated donor T cells by co-cultivation with a stroma layer of recipient cells and analyzed activation kinetics of CD3⁺, CD4⁺ and CD8⁺ T cells. Based on these data, activated cells were then depleted based on expression of activation-induced antigens using magnetic cell sorting (MACS). Alloreactivity of donor T cells was remarkably decreased after depletion of cells expressing either CD25 or CD69, as was shown in suitable in vitroassays. The lowest level of alloreactivity was found when both CD25- and CD69-positive cells were depleted. Importantly, depleted cell fractions preserved reactivity against third-party cells. In summary, we found that MACS-based ex vivo depletion of alloreactive cells may be a suitable way to prevent GVHD and therefore improve allogeneic BMT and adoptive immunotherapy. Bone Marrow Transplantation (2000) 25 , Suppl. 2, S39–S42.