HLA class I glycoproteins contain the functional sites that bind peptide antigens and engage lymphocyte receptors. Recently, clinical application of sequence-based HLA typing has uncovered an ...unprecedented number of novel HLA class I alleles. Here we define the nature and extent of the variation in 3,489 HLA-A, 4,356 HLA-B and 3,111 HLA-C alleles. This analysis required development of suites of methods, having general applicability, for comparing and analyzing large numbers of homologous sequences. At least three amino-acid substitutions are present at every position in the polymorphic α1 and α2 domains of HLA-A, -B and -C. A minority of positions have an incidence >1% for the 'second' most frequent nucleotide, comprising 70 positions in HLA-A, 85 in HLA-B and 54 in HLA-C. The majority of these positions have three or four alternative nucleotides. These positions were subject to positive selection and correspond to binding sites for peptides and receptors. Most alleles of HLA class I (>80%) are very rare, often identified in one person or family, and they differ by point mutation from older, more common alleles. These alleles with single nucleotide polymorphisms reflect the germ-line mutation rate. Their frequency predicts the human population harbors 8-9 million HLA class I variants. The common alleles of human populations comprise 42 core alleles, which represent all selected polymorphism, and recombinants that have assorted this polymorphism.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Natural killer (NK) cells have vital functions in human immunity and reproduction. In the innate and adaptive immune responses to infection, particularly by viruses, NK cells respond by secreting ...inflammatory cytokines and killing infected cells. In reproduction, NK cells are critical for genesis of the placenta, the organ that controls the supply of oxygen and nutrients to the growing fetus. Controlling NK cell functions are interactions of HLA class I with inhibitory NK cell receptors. First evolved was the conserved interaction of HLA-E with CD94:NKG2A; later established were diverse interactions of HLA-A, -B, and -C with killer cell immunoglobulin-like receptors. Characterizing the latter interactions is rapid evolution, which distinguishes human populations and all species of higher primate. Driving this evolution are the different and competing selections imposed by pathogens on NK cell-mediated immunity and by the constraints of human reproduction on NK cell-mediated placentation. Promoting rapid evolution is independent segregation of polymorphic receptors and ligands throughout human populations.
The fast evolving human KIR gene family encodes variable lymphocyte receptors specific for polymorphic HLA class I determinants. Nucleotide sequences for 24 representative human KIR haplotypes were ...determined. With three previously defined haplotypes, this gave a set of 12 group A and 15 group B haplotypes for assessment of KIR variation. The seven gene-content haplotypes are all combinations of four centromeric and two telomeric motifs. 2DL5, 2DS5 and 2DS3 can be present in centromeric and telomeric locations. With one exception, haplotypes having identical gene content differed in their combinations of KIR alleles. Sequence diversity varied between haplotype groups and between centromeric and telomeric halves of the KIR locus. The most variable A haplotype genes are in the telomeric half, whereas the most variable genes characterizing B haplotypes are in the centromeric half. Of the highly polymorphic genes, only the 3DL3 framework gene exhibits a similar diversity when carried by A and B haplotypes. Phylogenetic analysis and divergence time estimates, point to the centromeric gene-content motifs that distinguish A and B haplotypes having emerged ~6 million years ago, contemporaneously with the separation of human and chimpanzee ancestors. In contrast, the telomeric motifs that distinguish A and B haplotypes emerged more recently, ~1.7 million years ago, before the emergence of Homo sapiens. Thus the centromeric and telomeric motifs that typify A and B haplotypes have likely been present throughout human evolution. The results suggest the common ancestor of A and B haplotypes combined a B-like centromeric region with an A-like telomeric region.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Natural killer (NK) cells play critical roles in immune defense and reproduction, yet remain the most poorly understood major lymphocyte population. Because their activation is controlled by a ...variety of combinatorially expressed activating and inhibitory receptors, NK cell diversity and function are closely linked. To provide an unprecedented understanding of NK cell repertoire diversity, we used mass cytometry to simultaneously analyze 37 parameters, including 28 NK cell receptors, on peripheral blood NK cells from 5 sets of monozygotic twins and 12 unrelated donors of defined human leukocyte antigen (HLA) and killer cell immunoglobulin-like receptor (KIR) genotype. This analysis revealed a remarkable degree of NK cell diversity, with an estimated 6000 to 30,000 phenotypic populations within an individual and >100,000 phenotypes in the donor panel. Genetics largely determined inhibitory receptor expression, whereas activation receptor expression was heavily environmentally influenced. Therefore, NK cells may maintain self-tolerance through strictly regulated expression of inhibitory receptors while using adaptable expression patterns of activating and costimulatory receptors to respond to pathogens and tumors. These findings further suggest the possibility that discrete NK cell subpopulations could be harnessed for immunotherapeutic strategies in the settings of infection, reproduction, and transplantation.
Human NK cells are usually defined as CD3
-
CD56
+
lymphocytes. However, a CD56
-
CD16
+
(CD56neg) lymphocyte population that displays NK-associated markers expands during chronic viral infections ...such as HIV-1 and HCV, and, to lesser extent, in herpesvirus infections. This CD56neg NK cell subset has been understudied because it requires the exclusion of other lymphocytes to accurately identify its presence. Many questions remain regarding the origin, development, phenotype, and function of the CD56neg NK cell population. Our objective was to determine the frequency of this NK subset in healthy controls and its alteration in viral infections by performing a meta-analysis. In addition to this, we analyzed deposited CyTOF and scRNAseq datasets to define the phenotype and subsets of the CD56neg NK cell population, as well as their functional variation. We found in 757 individuals, from a combined 28 studies and 6 datasets, that the CD56neg subset constitutes 5.67% of NK cells in healthy peripheral blood, while HIV-1 infection increases this population by a mean difference of 10.69%. Meta-analysis of surface marker expression between NK subsets showed no evidence of increased exhaustion or decreased proliferation within the CD56neg subset. CD56neg NK cells have a distinctive pattern of KIR expression, implying they have a unique potential for KIR-mediated education. A perforin
-
CD94
-
NKG2C
-
NKp30
-
CD56neg population exhibited different gene expression and degranulation responses against K562 cells compared to other CD56neg cells. This analysis distinguishes two functionally distinct subsets of CD56neg NK cells. They are phenotypically diverse and have differing capacity for education by HLA class-I interactions with KIRs.
Summary
Shaping natural killer (NK) cell functions in human immunity and reproduction are diverse killer cell immunoglobulin‐like receptors (KIRs) that recognize polymorphic MHC class I determinants. ...A survey of placental mammals suggests that KIRs serve as variable NK cell receptors only in certain primates and artiodactyls. Divergence of the functional and variable KIRs in primates and artiodactyls predates placental reproduction. Among artiodactyls, cattle but not pigs have diverse KIRs. Catarrhine (humans, apes, and Old World monkeys) and platyrrhine (New World monkeys) primates, but not prosimians, have diverse KIRs. Platyrrhine and catarrhine systems of KIR and MHC class I are highly diverged, but within the catarrhines, a stepwise co‐evolution of MHC class I and KIR is discerned. In Old World monkeys, diversification focuses on MHC‐A and MHC‐B and their cognate lineage II KIR. With evolution of C1‐bearing MHC‐C from MHC‐B, as informed by orangutan, the focus changes to MHC‐C and its cognate lineage III KIR. Evolution of C2 from C1 and fixation of MHC‐C drove further elaboration of MHC‐C‐specific KIR, as exemplified by chimpanzee. In humans, the evolutionary trajectory changes again. Emerging from reorganization of the KIR locus and selective attenuation of KIR avidity for MHC class I are the functionally distinctive KIR A and KIR B haplotypes.
The human killer cell Ig-like receptor (KIR) locus comprises two groups of KIR haplotypes, termed A and B. These are present in all human populations but with different relative frequencies, ...suggesting they have different functional properties that underlie their balancing selection. We studied the genomic organization and functional properties of the alleles of the inhibitory and activating HLA-C receptors encoded by KIR haplotypes. Because every HLA-C allotype functions as a ligand for KIR, the interactions between KIR and HLA-C dominate the HLA class I-mediated regulation of human NK cells. The C2 epitope is recognized by inhibitory KIR2DL1 and activating KIR2DS1, whereas the C1 epitope is recognized by inhibitory KIR2DL2 and KIR2DL3. This study shows that the KIR2DL1, KIR2DS1, and KIR2DL2/3 alleles form distinctive phylogenetic clades that associate with specific KIR haplotypes. KIR A haplotypes are characterized by KIR2DL1 alleles that encode strong inhibitory C2 receptors and KIR2DL3 alleles encoding weak inhibitory C1 receptors. In striking contrast, KIR B haplotypes are characterized by KIR2DL1 alleles that encode weak inhibitory C2 receptors and KIR2DL2 alleles encoding strong inhibitory C1 receptors. The wide-ranging properties of KIR allotypes arise from substitutions throughout the KIR molecule. Such substitutions can influence cell surface expression, as well as the avidity and specificity for HLA-C ligands. Consistent with the crucial role of inhibitory HLA-C receptors in self-recognition, as well as NK cell education and response, most KIR haplotypes have both a functional C1 and C2 receptor, despite the considerable variation that occurs in ligand recognition and surface expression.
Killer-cell immunoglobulin-like receptor (KIR) genes form a diverse, immunogenetic system. Group A and B KIR haplotypes have distinctive centromeric (Cen) and telomeric (Tel) gene-content motifs. ...Aiming to develop a donor selection strategy to improve transplant outcome, we compared the contribution of these motifs to the clinical benefit conferred by B haplotype donors. We KIR genotyped donors from 1409 unrelated transplants for acute myelogenous leukemia (AML; n = 1086) and acute lymphoblastic leukemia (ALL; n = 323). Donor KIR genotype influenced transplantation outcome for AML but not ALL. Compared with A haplotype motifs, centromeric and telomeric B motifs both contributed to relapse protection and improved survival, but Cen-B homozygosity had the strongest independent effect. With Cen-B/B homozygous donors the cumulative incidence of relapse was 15.4% compared with 36.5% for Cen-A/A donors (relative risk of relapse 0.34; 95% confidence interval 0.2-0.57; P < .001). Overall, significantly reduced relapse was achieved with donors having 2 or more B gene-content motifs (relative risk 0.64; 95% confidence interval 0.48-0.86; P = .003) for both HLA-matched and mismatched transplants. KIR genotyping of several best HLA-matched potential unrelated donors should substantially increase the frequency of transplants by using grafts with favorable KIR gene content. Adopting this practice could result in superior disease-free survival for patients with AML.
Natural killer (NK) cells have diverse roles in hominid immunity and reproduction. Modulating these functions are the interactions between major histocompatibility complex (MHC) class I molecules ...that are ligands for two NK cell surface receptor types. Diverse killer cell immunoglobulin-like receptors (KIR) bind specific motifs encoded within the polymorphic MHC class I cell surface glycoproteins, while, in more conserved interactions, CD94:NKG2A receptors recognize MHC-E with bound peptides derived from MHC class I leader sequences. The hominid lineage presents a choreographed co-evolution of KIR with their MHC class I ligands.
, and
are present in all great apes with species-specific haplotypic variation in gene content. The Bw4 epitope recognized by lineage II KIR is restricted to MHC-B but also present on some gorilla and human MHC-A. Common to great apes, but rare in humans, are MHC-B possessing a C1 epitope recognized by lineage III KIR.
arose from duplication of
and is fixed in all great apes except orangutan, where it exists on approximately 50% of haplotypes and all allotypes are C1-bearing. Recent study showed that gorillas possess yet another intermediate
organization compared to humans. Like orangutans, but unlike the
species, duplication of
occurred. However,
is fixed, and the MHC-C C2 epitope (absent in orangutans) emerges. The evolution of MHC-C drove expansion of its cognate lineage III KIR. Recently, position -21 of the MHC-B leader sequence has been shown to be critical in determining NK cell educational outcome. In humans, methionine (-21M) results in CD94:NKG2A-focused education whereas threonine (-21T) produces KIR-focused education. This is another dynamic position among hominids. Orangutans have exclusively -21M, consistent with their intermediate stage in lineage III KIR-focused evolution. Gorillas have both -21M and -21T, like humans, but they are unequally encoded by their duplicated
genes. Chimpanzees have near-fixed -21T, indicative of KIR-focused NK education. Harmonious with this observation, chimpanzee KIR exhibit strong binding and, compared to humans, smaller differences between binding levels of activating and inhibitory KIR. Consistent between these MHC-NK cell receptor systems over the course of hominid evolution is the evolution of polymorphism favoring the more novel and dynamic KIR system.
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The transient receptor potential melastatin-3 (TRPM3) channel belongs to the family of transient receptor potential (TRP) cation channels that are expressed in a variety of tissues ...and cell types, including dorsal root ganglia, cardiomyocytes and pancreatic beta-cells. Although its natural ligands are currently unknown, TRPM3 channels can be activated by the neurosteroid pregnenolone sulfate, the synthetic ligand CIM0216, and by noxious heat. TRPM3 channels are regulated by phosphoinositides, and perhaps by calmodulin. Stimulation of TRPM3 induces an intracellular signaling cascade involving a rise in intracellular Ca2+, activation of the protein kinases Raf, ERK and JNK, and the activation of the stimulus-responsive transcription factors AP-1, CREB, Egr-1, and Elk-1. Functionally, stimulation of TRPM3 channels is connected with heat sensation by somatosensory neurons, insulin secretion by pancreatic beta-cells, regulation of neurotransmitter release, iris constriction, and tumor promotion. With the development of highly specific activators and inhibitors of TRPM3 channels, we expect that additional tissue-specific functions of TRPM3 channels will be discovered, establishing TRPM3 channels as a new therapeutic target.
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