KIR ligand incompatibility is not associated with relapse reduction after double umbilical cord blood transplantation

摘要

Natural killer (NK) cell alloreactivity has been implicated in graft-versus-host (GVH) and GVL immunity. Though the basic mechanisms of NK cell alloreactivity are well described, comparatively little is known about its clinical effects. NK cells contribute to immunity against malignant and virally infected cells through their ability to recognize and directly kill host cells that have downregulated MHC-I. There is no Ag specificity or requirement for prior sensitization. Instead, cytotoxicity towards a particular target cell is regulated by a balance of activating and inhibitory cell-cell contacts.1 An important and proximal factor in this regulation is the inhibitory signal created when inhibitory killer Ig-like receptors (KIR) on NK cells engage MHC-I molecules on target cells.2 Conversely, the absence of HLA class I on a target cell allows other activating signals to dominate, and leaves the target vulnerable to lysis.