Trogocytosis in allogeneic transplants: donor cells take on the recipients identity.

Trogocytosis has been identified as a mechanism of cell communication between immune cells. Unlike the more common receptor-ligand signaling, trogocytosis results in the transfer of intact and functional surface proteins between cells. For example, antigen presenting cells in contact with T cells exchange proteins which results in the T-cell acquiring antigen presentation capabilities. This allows for the newly activated T cells to stimulate other T cells thus amplifying the immune response. We have recently demonstrated that during allogeneic hematopoietic stem cell transplantation the donor cells obtain recipient MHC class I proteins by trogocytosis. The effect is a donor cell that can masquerade as a recipient cells and evade detection by NK cells and macrophages.