Killer immunoglobulin-like receptors (KIRs) play an essential role in the regulation of natural killer cell functions. KIR genes are highly polymorphic in nature, showing both haplotypic and allelic variations among people. We demonstrated in both in vitro and in vivo models a significant heterogeneity in function among different KIR2DL1 alleles, including their ability to inhibit YT-Indy cells from degranulation, interferon ␥ production, and cytotoxicity against target cells expressing the HLA-Cw6 ligand. Subsequent experiments showed that the molecular determinant was an arginine residue at position 245 (R245) in its transmembrane domain that mechanistically affects both the efficiency of inhibitory signaling and durability of surface expression. Specifically, in comparison with R245-negative alleles, KIR2DL1 that included R245 recruited more Src-homology-2 domaincontaining protein tyrosine phosphatase 2 and ␤-arrestin 2, showed higher inhibition of lipid raft polarization at immune synapse, and had less down-regulation of cell-surface expression upon interaction with its ligand. Thus, our findings provide novel insights into the molecular determinant of KIR2DL1 and conceivably a fundamental understanding of KIR2DL1 allelic polymorphism in human disease susceptibility, transplant outcome, and donor selection. (Blood. 2009;114:5182-5190) IntroductionNatural killer (NK) cells are a part of our immune system that eliminates virally infected cells and tumor cells through cytolytic killing and cytokine secretion. 1 An NK cell's responses to its targets are regulated by the balance of signals generated through various activating and inhibiting receptors. 2,3 NK-cell receptors may be categorized on the basis of their ligand specificity for major histocompatibility complex class I and related molecules. Expression of various combinations of receptors on the surface of NK cells creates a diverse repertoire. 4,5 In humans, one of the most important groups of receptors that regulate NK-cell function is killer immunoglobulin-like receptors (KIRs). 6,7 The KIRs make up a family of diverse glycoproteins encoded by a compact cluster of genes located on human chromosome 19q13.4. 8,9 KIRs expressed at the surface of NK cells regulate their response by interacting with human leukocyte antigen (HLA) class I molecules. The KIR family has both activating and inhibitory receptors. KIR inhibitory receptors suppress NK cells' function using the immunoreceptor tyrosine-based inhibitory motif in their long cytoplasmic tails. Activating KIR receptors have short cytoplasmic tails and do not contain the inhibitory motif.Each of the KIR genes exhibits allelic variation as well as haplotypic variability in terms of the number and types of genes on the haplotypes. 9,10 The allelic variations of KIR genes range from 2 to more than 30. 10 The polymorphisms between the alleles of a given KIR gene can occur in its extracellular, transmembrane, or cytoplasmic domains. Polymorphism at each of these 3 domains has been associated with significant bi...

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Killer-cell immunoglobulin-like receptors (KIRs) on natural killer (NK) cells have been linked to a wide spectrum of health conditions such as chronic infections, autoimmune diseases, pregnancy complications, cancers, and transplant failures. A small subset of effector memory T cells also expresses KIRs. Here, we use modern analytic tools including genome-wide and multiplex molecular, phenotypic, and functional assays to characterize the KIR+ T cells in human blood. We find that KIR+ T cells primarily reside in the CD56+ T population that is distinctively DNAM-1high with a genome-wide quiescent transcriptome, short telomere, and limited TCR excision circles. During cytomegalovirus (CMV) reactivation in bone marrow transplant recipients, KIR+CD56+ T cells rapidly expanded in real-time, but not KIR+CD56− T cells or KIR+ NK cells. In CMV+ asymptomatic donors, as much as 50% of CD56+ T cells are KIR+, and most are distinguishably KIR2DL2/3+NKG2C+CD57+. Functionally, the KIR+CD56+ T-cell subset lyses cancer cells and CMVpp65-pulsed target cells in a dual KIR-dependent and TCR-dependent manner. Analysis of metabolic transcriptome confirms the immunological memory status of KIR+CD56+ T cells, in contrast to KIR−CD56+ T cells that are more active in energy metabolism and effector differentiation. KIR−CD56+ T cells have >25-fold higher level of expression of RORC than the KIR+ counterpart and are a previously unknown producer of IL-13 rather than IL-17 in multiplex cytokine arrays. Our data provide fundamental insights intoKIR + T cells biologically and clinically.

Zona pellucida (ZP) is a glycoproteinaceous translucent matrix that surrounds the mammalian oocyte and plays a critical role in the accomplishment of fertilization. In humans, it is composed of 4 glycoproteins designated as ZP1, ZP2, ZP3 and ZP4, whereas mouse ZP is composed of ZP1, ZP2 and ZP3 (Zp4 being a pseudogene). In addition to a variable sequence identity of a given zona protein among various species, human ZP1 and ZP4 are paralogs and mature polypeptide chains share an identity of 47%. Employing either affinity purified native or recombinant human zona proteins, it has been demonstrated that ZP1, ZP3 and ZP4 bind to the capacitated human spermatozoa and induce an acrosome reaction, whereas in mice, ZP3 acts as the putative primary sperm receptor. Human ZP2 only binds to acrosome-reacted spermatozoa and thus may be acting as a secondary sperm receptor. In contrast to O-linked glycans of ZP3 in mice, N-linked glycans of human ZP3 and ZP4 are more relevant for induction of the acrosome reaction. Recent studies suggest that Sialyl-Lewis(x) sequence present on both N- and O-glycans of human ZP play an important role in human sperm-egg binding. There are subtle differences in the downstream signaling events associated with ZP3 versus ZP1/ZP4-mediated induction of the acrosome reaction. For example, ZP3 but not ZP1/ZP4-mediated induction of the acrosome reaction is dependent on the activation of the Gi protein-coupled receptor. Thus, various studies suggest that, in contrast to mice, in humans more than one zona protein binds to spermatozoa and induces an acrosome reaction.