Specificity of two anti-class I HLA monoclonal antibodies that block class I recognition by the NKB1 killer cell inhibitory receptor

Killer-cell immunoglobulin-like receptors and cytomegalovirus reactivation during late pregnancy

Human cytomegalovirus (CMV) represents an important public health concern as it is associated with severe morbidity and mortality in transplant recipients, HIV-infected individuals and pregnant women given the risk of congenital infection. Congenital CMV is a leading cause of neurological sequelae, developmental delay and birth defects worldwide. Cytomegalovirus can be transmitted to the foetus following maternal infection or reactivation. NK cells expressing killer-cell immunoglobulin-like receptors (KIR) are part of the innate immune system and the first line of defence against viral incursions. Previous reports have shown that KIR genes are associated with CMV infections in the post-transplant setting. In this study, we set out to determine whether a protective effect of KIR genes over CMV infection is seen in Mexican pregnant women. Cytomegalovirus infection was assessed through nucleic acid testing in 200 pregnant women and 600 healthy blood donors comprising the Mexican mestizo reference population. Killer-cell immunoglobulin-like receptors and HLA-C genotypes were obtained from 200 pregnant women and 300 reference samples using a comprehensive PCR-SSP approach. We observed statistically lower carrier frequencies of cB03|tA01 gene-content haplotype, of cB03 haplotype motif, of the KIR2DL5 + 2DS3/2DS5 gene pair and of KIR2DL5 amongst CMV-positive pregnant women in comparison with those CMV negative. None of these were associated with CMV status in the reference population. Logistic regression analysis revealed that the most important factor determining CMV status during third-trimester pregnancies was the KIR2DL5 + 2DS3/2DS5 gene pair (OR 0.376 (95%CI 0.174, 0.811, P = 0.013). Our results indicate that CMV-protective KIR gene associations described in Caucasoid populations are also present in the genetically distinct Mexican mestizo population. Our results suggest that certain KIR gene combinations provide protection against CMV infections occurring during late-term pregnancies, a finding of utmost epidemiological importance given its implication with congenital CMV infections.

Killer-cell immunoglobulin-like receptors (KIR) in severe A (H1N1) 2009 influenza infections

Introduction of a novel influenza virus into the human population leads to the occurrence of pandemic events, such as the one caused by pandemic influenza A (H1N1) 2009 virus. The severity of infections caused by this virus in young adults was greater than that observed in patients with seasonal influenza. Fatal cases have been associated with an abnormal innate, proinflammatory immune response. A critical role for natural killer cells during the initial responses to influenza infections has been suggested. In this study, we assessed the association of killer-cell immunoglobulin-like receptors (KIRs) with disease severity by comparing KIR gene content in patients with mild and severe pandemic influenza virus infections to a control group. We found that activator (KIR3DS1 and KIR2DS5) and inhibitory (KIR2DL5) genes, encoded in group B haplotypes containing the cB01, cB03 and tB01 motifs, are associated with severe pandemic influenza A (H1N1) 2009 infections. Better understanding of how genetic variability contributes to influenza virus pathogenesis may help to the development of immune intervention strategies aiming at controlling the severity of disease.

The first Ig domain of KIR3DL1 contacts MHC class I at a secondary site

KIR3DL1 is a highly polymorphic inhibitory killer cell Ig-like receptor (KIR) implicated in resistance to viral diseases such as AIDS. KIR3DL1 contains three Ig domains and is specific for MHC class I (MHC-I) molecules belonging to the HLA-Bw4 serogroup. The receptor's second and third Ig domains confer the Bw4 specificity, but the role of the first Ig domain (D0) in ligand recognition has remained enigmatic. We found that KIR3DL1 expressed in YTS cells and as a soluble receptor can weakly recognize additional MHC-I molecules including HLA-B*0702 and HLA-G. This interaction is highly sensitive to blocking with Abs to the MHC-I α3-domain and the anti-KIR3DL1 Ab Z27, but not the canonical blocking Ab DX9. Using chimeric receptors between KIR3DL1 and KIR2DL1 expressed on YTS cells and as soluble Fc-fusion proteins, we show that the D0 domain confers the broad functional recognition and binding as well as the reactivity with Z27. These results suggest that the presence of a second and independent site of interaction between D0 and MHC-I and that MHC-I could bridge KIR3DL1 molecules together in a manner that facilitates signaling.

Immunotherapy for pediatric cancer

Improvements in adult cancer survivorship can be achieved from behavioral changes and adopting screening programs. Yet, these approaches cannot be readily applied to lower the morbidity and mortality from childhood cancers. Rather, pediatric oncologists must rely on procedures and therapies to treat, rather than prevent malignancies. The systematic application of chemotherapy, radiation therapy, and surgery has led to remarkable advances in survival but these improvements have come at a cost. Children routinely receive chemotherapy agents that were designed decades ago, and these drugs have predictable side effects that result in the loss of potential for long-term survivors. The advent of targeted applications of immune-based therapies offers children with cancer a new class of oncolytic therapies that may be used to treat disease refractory to conventional approaches and lessen the toxicity of current treatment regimens without compromising remission. This review explores how 3 components of the immune system--T cells, natural killer (NK) cells, and antibodies--can be used for therapy of pediatric malignancies.

Killer cell immunoglobulin-like receptors on NK cells: the how, where and why

Natural killer (NK) cells have killer cell immunoglobulin-like receptors (KIR) that recognize and interact with HLA class I antigen. The KIRs are a multigene family and its members are often highly polymorphic. Evidence is emerging from disease-association studies that KIR receptors can play beneficial roles in viral infections, such as HIV, HCV, but may also predispose to certain autoimmune diseases. Knowledge regarding expression and function of KIR on human NK cells is lagging behind the rapid expansion of sequencing and genetic data already generated. This review focuses on recent discoveries that have been made, which help bridge this gap. We now appreciate the importance of phenotypic diversity of KIR receptor expression in NK cells and are starting to unravel some of the mysteries surrounding control of their complex expression patterns. In particular, the role that HLA ligand contributes to KIR receptor expression will be discussed. It is also becoming increasingly clear that genetic factors, such as promoters and epi-genetic mechanisms such as methylation, are hugely important in controlling NK cell receptor expression and function. The relevance of phenotypic diversity of NK cell receptors will be discussed in light of these recent findings.

Killer Cell Inhibitory Receptors for MHC Class I Molecules Regulate Lysis of Melanoma Cells Mediated by NK cells, γδ T Cells, and Antigen-Specific CTL

NK cells and T cells express killer cell inhibitory receptors (KIR) recognizing polymorphic MHC class I molecules. Although prior studies have established that MHC class I can protect normal and transformed hematopoietic cells from NK cell lysis, the role of MHC class I on the recognition of solid tumors has been controversial. In this study, we investigated whether interactions of KIR with their ligands on melanoma tumor cells could inhibit tumor cell lysis by NK and γδ T cell clones. Ligation of the NK cell receptor KIR3DL1 by HLA-Bw4 allotypes resulted in inhibition of cytotoxicity against HLA-B*4403-transfected melanomas as well as against melanomas endogenously expressing HLA-Bw4 allotypes. Similarly, interactions of KIR2DL2 or KIR2DL3 (KIR2DL2/3) with HLA-Cw3-related allotypes on melanomas resulted in decreased tumor cell lysis. We also investigated whether signaling via KIR affected melanoma recognition by CTL. Introduction of KIR3DL1 molecules into HLA-A*0201-restricted gp100-specific CTL resulted in inhibition of lysis of gp100+ melanomas co-expressing HLA-A*0201 and HLA-Bw4 allotypes. These results suggest that disrupting interactions of KIR with their ligands on tumor cells in vivo may enhance antitumor responses mediated by both innate and adaptive immune effector cells.