Only in recent years, attentions have been drawn to the significance of expressing killer cell inhibitory receptors (KIR) in T cells KIRs specifically bind to the corresponding region of the MHC class I molecules and transmit negative signals to prevent cytotoxity of T cells. When the ligands of KIRs are missing, the lysis of the target cells can’t be avoided. Perhaps the existence of KIRs is the main mechanism for preventing T cells from attacking autologous tissues. The recognition mechanism of the interaction between the KIR + donor T cells and the recipient’s MHC class I molecule expressing tissue cells might shed light on the establishment of the immunotolerance for the prevention of allo-graft rejection and graft-versus-host disease.
