NK-KIR Transcript Kinetics Correlate With Acute Graft-Versus-Host Disease Occurrence After Allogeneic Bone Marrow Transplantation

Dynamic mRNA expression of donor-derived activating KIR genes and their significant effects on clinical outcome after haematopoietic stem cell transplantation

Numerous reports suggest that activating killer immunoglobulin-like receptors (aKIRs) of natural killer (NK) cells, in addition to inhibitory KIRs (iKIRs), play a prognostic role after allogeneic haematopoietic stem cell transplantation (allo-HSCT). We aimed to investigate the association between the dynamic expression of KIRs on NK cells and the outcomes, particularly regarding graft-versus-host disease (GvHD). This study retrospectively enrolled 260 pairs of donors and recipients who had undergone allo-HSCT without in-vitro T cell depletion. The mRNA transcription level of KIRs was determined by quantitative real-time polymerase chain reaction (RT-qPCR). The levels of aKIR transcripts were decreased more than those of iKIRs during the occurrence of GvHD. The transcription levels of KIR2DS2 and KIR2DS4 in the patients developing GvHD, compared with those who were at a tolerance state, showed the most significant decrease in the month at their peak transcription levels (p = 0.03, p = 0.002). Significantly decreased expression of KIR2DS1 (p = 0.02), KIR2DS3 (p = 0.04) and KIR2DS5 (p = 0.04) in the GvHD group was observed when the transcription level reached a maximum. High expression of KIR3DS1 was associated with superior overall survival (OS) (p < 0.001). The expression of KIR2DS4 in the KIR genotype Bx group decreased more during GvHD, particularly at 3M (p = 0.02). These findings suggest that KIR genes are potential post-HSCT biomarkers and dynamic changes in the KIR transcription levels can be detected to better predict the occurrence and evaluate the treatment of GvHD after transplantation.

Study of KIR gene expression at the mRNA level in specific donor-derived NK cells after allogeneic HSCT

The function of natural killer (NK) cells after allogeneic hematopoietic stem cell transplantation (allo-HSCT) is regulated by the balance between inhibitory KIRs (iKIRs) and activating KIRs (aKIRs). However, few studies have examined the subsequent expression of KIR genes unique to the donor. We defined the set of KIR genes expressed only in the donor and designed a method for measuring the expression of these KIR genes by quantitative real-time polymerase chain reaction (RT-qPCR) based on genetic cloning techniques. In this study, we evaluated the recovery pattern of KIR genes in 252 donor-recipient pairs. The expression of each KIR unique to the donor was in line with that of KIR genes shared by the donor and recipient, such as KIR2DS1, KIR3DS1, KIR2DS4, or KIR2DS3. The timing of the peak mRNA expression of aKIRs unique to the donor was inconsistent but occurred within the first 3 months posttransplantation, whereas the peak mRNA expression of iKIRs was consistently observed in the third month after transplantation. The expression of KIR2DL2 in the third month posttransplantation was significantly higher in the transplant recipients than in the donors (p = 0.01). The KIR2DL1 and KIR3DL1 levels in the transplant recipients in the second and third months posttransplantation were also obviously higher than the donor levels (p < 0.0001). Thus, these observations should be considered when attempting to predict the correlation between mRNA expression and prognosis after allo-HSCT.

Natural killer cells and killer-cell immunoglobulin-like receptor polymorphisms: their role in hematopoietic stem cell transplantation

Natural killer (NK) cells are important effector cells in the early control of infected, malignant, and "nonself" cells. Various receptor families are involved in enabling NK cells to detect and efficiently eliminate these target cells. The killer-cell immunoglobulin-like receptor (KIR) family is a set of receptors that are very polymorphic with regard to gene content, expression level, and expression pattern. KIRs are responsible for the induction of a NK cell alloreactive response through their interaction with HLA class I molecules. The role of NK cells in hematopoietic stem cell transplantation (HSCT) has been studied for many years, and induction of antileukemic responses by donor NK cells has been reported. Conflicting data still exist on the exact circumstances in which the KIR repertoire affects and influences clinical outcome after HSCT. More large-scale studies are needed on well-defined cohorts to unravel the mechanism of action of the NK cell-mediated alloresponse in an HSCT setting.

KIR3DL1 genetic diversity and phenotypic variation in the Chinese Han population

Allelic polymorphism and expression variation of killer cell immunoglobulin-like receptor (KIR) 3DL1 on natural killer (NK) cells differ among populations. To determine whether the phenotypic variants are due to KIR polymorphism, transcription or copy number, the allelic polymorphism, mRNA levels and antigen expression of KIR3DL1 were assessed in 162 individuals. We characterized 13 KIR3DL1 alleles, five of which were novel. In addition, 21 genotypes were identified. The correlation between the binding patterns of NK cells to anti-KIR3DL1 and KIR3DL1 alleles was also examined. NK cells with different 3DL1 alleles showed distinct binding levels to anti-KIR3DL1. The binding frequencies of NK cells to anti-KIR3DL1 were not accordant with their binding levels, but both associated with the allele copy numbers. The mRNA expression amounts of individuals with two copy alleles were higher than those of individuals with one copy allele. Our data indicate that both the allele copy number and polymorphism of KIR3DL1 influence the antigen expression on the NK-cell surface, but only the copy number was associated with mRNA expression.

Determination of donor-derived killer immunoglobulin-like receptor (KIR) by sequential genotyping in hematopoietic stem cell-transplanted patients

Donor killer immunoglobulin-like receptor (KIR) and KIR-ligand mismatch is considered vital in clarifying the mechanism of natural killer (NK) cell alloreactivity in hematopoietic stem cell transplantation (HSCT). In practical terms, however, it may be difficult to analyze the KIR genotype of donor cells directly as all donor cells are used for the transplant rather than for research purposes. To accurately estimate donor KIR genotype, we determined recipient KIR genotyping sequentially, at a minimum of two time points, using 19 KIR-specific primers in 10 patients who underwent HSCT. Among 10 patients, four had a KIR-ligand mismatch in the graft versus host direction. Sequential KIR genotyping showed the genotype changes at the time of engraftment (donor-derived) as well as relapse (recipient-derived). Our results highlight the utility of sequential KIR genotyping to better understand ligand-ligand, KIR-KIR, or ligand-KIR mismatches. Further studies, including a functional assay of NK cells may clarify the underlying mechanism of KIR ligand-donor KIR mismatch in HSCT.

Differential RNA expression of KIR alleles

Allelic polymorphisms dramatically influence the phenotype of human killer immunoglobulin-like receptors (KIR) by modifying their expression in cell surfaces. It is unclear though to what extent this involves transcriptional or post-transcriptional mechanisms, as quantitative RNA expression of KIR alleles has not been systematically compared. We measured RNA transcript abundance of common KIR alleles by real-time quantitative reverse transcriptase PCR (RT-PCR) in 85 PBL samples that were allele-typed in parallel. Allele type showed little influence on transcript abundance for a given KIR gene, except for: (1) KIR2DL5B*002, which consistently showed undetectable transcripts levels; (2) truncated KIR2DS4 alleles, associated with lowered expression levels; and (3) alleles of KIR2DL4 with a single-base deletion, associated with higher expression than average. Lowered levels of truncated KIR2DS4 transcripts were confirmed by dot blot of RT-PCR products, indicating imbalanced allelic RNA expression in heterozygote genotypes containing these alleles. Imbalanced expression of truncated KIR2DS4 alleles was corroborated in family samples. Gene copy number of KIR2DL1, KIR2DL3 and KIR3DL1 influenced RNA expression, genotypes with a single copy expressing on average lower transcript amounts than those with two copies. The data show that for a given KIR gene, the common allele types found in our population express comparable RNA levels, except truncated or null alleles. Thus, variation of KIR expression on cell surfaces more likely involves post-transcriptional mechanisms.

A novel approach for quantification of KIR expression in healthy donors and pediatric recipients of hematopoietic SCTs

The killer cell Ig-like receptor (KIR) expression repertoire may offer valuable information for hematopoietic SCT (HSCT). We designed a quantitative KIR RNAtype assay and used it to determine KIR gene expression in healthy donors and patients before HSCT. The specificity of the assay was ensured by specific primers and by electrophoretic distinction of PCR products of unique length. In 87 healthy donors, the KIR repertoire was broadly distributed (32 categories of profiles). There was an overall trend toward inverse correlation of KIR expression level and donor age. Age affected mainly the activating KIR families. Leukemia patients showed lower KIR expression before transplantation than healthy donors. Stem cell mobilization caused a transient increase of KIR expression. We conclude that KIR expression differs quantitatively with age and primary disease and is transiently altered by stem cell recruitment and selection.

Influence of killer immunoglobulin-like receptor/HLA ligand matching on achievement of T-cell complete donor chimerism in related donor nonmyeloablative allogeneic hematopoietic stem cell transplantation

Achievement of complete donor chimerism (CDC) after allogeneic nonmyeloablative hematopoietic stem cell transplantation (NMHSCT) is important for preventing graft rejection and for generating a graft-vs-malignancy effect. The alloreactivity of NK cells and some T-cell subsets is mediated through the interaction of their killer immunoglobulin-like receptors (KIRs) with target cell HLA/KIR ligands. The influence of KIR matching on the achievement of T-cell CDC after NMHSCT has not been previously described. We analyzed 31 patients undergoing T-cell replete related donor NMHSCT following fludarabine and 200 cGy TBI. Recipient inhibitory KIR genotype and donor HLA/KIR ligand matches were used to generate an inhibitory KIR score from 1 to 4 based upon the potential number of recipient inhibitory KIRs that could be engaged with donor HLA/KIR ligands. Patients with a score of 1 were less likely to achieve T-cell CDC (P=0.016) and more likely to develop graft rejection (P=0.011) than those with scores greater than 1. Thus, patients with lower inhibitory KIR scores may have more active anti-donor immune effector cells that may reduce donor chimerism. Conversely, patients with greater inhibitory KIR scores may have less active NK cell and T-cell populations, which may make them more likely to achieve CDC.

Genetic diversity of KIR natural killer cell markers in populations from France, Guadeloupe, Finland, Senegal and Réunion

Killer cell immunoglobulin-like receptors (KIRs) belong to a diverse family of natural killer (NK) cell receptors recognizing human leukocyte antigen (HLA) class I molecules. Due to this functional link, KIR molecules are expected to display a high polymorphism, such as their HLA ligands. Moreover, many studies conducted in mouse and human models have shown that NK-KIR receptors play an important role in haematopoietic stem cell transplantation (HSCT). A beneficial impact of peculiar KIR ligand (HLA) mismatching has been reported suggesting a role to this combinatory HLA-KIR polymorphism. It is thus important to investigate KIR diversity in various human populations. To this end, we used polymerase chain reaction-sequence-specific primers to evaluate KIR gene in five selected populations (France, Guadeloupe, Senegal, Finland and Réunion). Genotypic and haplotypic frequencies were computed, as well as genetic distances and dendrogram (phylip package). These data illustrate the genetic relationship of these five populations through the KIR polymorphism. Results revealed a wide diversity in KIR gene frequencies in Guadeloupe and Réunion, and a high specificity in Senegal. The obtained dendrogram indicated small genetic distances between France, Guadeloupe and Réunion as well as between France and Finland. Senegal showed a distant genetic relationship with the other countries and, interestingly, an inverted ratio of coding/non-coding (KIR2DS4/1D) alleles compared with Caucasians. These data expose the broad diversity in KIR genes worldwide and show that KIR genes are pertinent tools in human population genetics. If the role of KIR donor-recipient incompatibilities is confirmed, KIR diversity according to ethnicity should be taken into account during the selection of HSCT donors.

KIR matching in hematopoietic stem cell transplantation

Although the key role of MHC-restricted T lymphocytes in hematopoietic stem cell transplantation (HSCT) has been known for a long time, recent data have focused on complementary or alternative effector cell populations, and in particular on NK cells. Spontaneously generated NK cell alloreactivity from stem cell grafts involves specific interactions between NK receptors, including killer immunoglobulin-like receptors (KIRs) and their MHC class I ligands. The combined effects of HLA and KIR polymorphic genes might explain discrepancies in the impact of donor-recipient matching observed in HSCT.