Figure 5.
Schematic model for MSC-mediated coengraftment of 2 allogeneic cord blood cells. UCB units contained primitive HSCs and differentiated cells, including lymphocytes. During the early phase of engraftment, the allogeneic immune responses by innate lymphocytes (lymphocytes contained in the graft) may be suppressed by cotransplanted MSCs because of the MSC's inhibitory effects on lymphocytes. Primitive HSCs are, therefore, protected from the alloimmune responses; thus, surviving HSCs induce tolerance to cells matched to their own genotypes. Therefore, though coinfused MSCs do not home to bone marrow and do not exist throughout the period of marrow reconstitution, mixed chimerism established during the early phase of engraftment with MSCs may be maintained for longer periods of engraftments.