Graphic summary of data. During the interaction between NK cells and MHC-mismatched DCs, the mismatched MHC may not be recognized by NK cell inhibitory receptors, and the lytic action elicited by activating receptors is allowed to proceed.^4,5 The NK cell alloreaction triggers DCs to transcribe the B2M gene and to synthesize and release B2M. B2M signals thymic and BM stroma to produce cKIT-L and IL-7 that mediate accelerated post-BMT immune reconstitution.