Fig. 2.

Schematic representation of factors which influence the outcome of pluripotent stem cell transplantations. Besides graft-related factors, such as pluripotency and therapeutic efficacy, host-related factors in first line immune-mediated rejection mechanisms have to be taken into consideration to understand the outcome of transplantations of pluripotent stem cells or their differentiation products. Possible outcomes include rejection, engraftment, teratoma formation, or growth of lineage-restricted tumors. Host factors presumably explain some of the variations observed with different cell types in different experimental transplantation models