Killer-cell immunoglobulin-like receptors on the cusp of modern immunogenetics

Lack of association of the KIR and HLA class I ligands with ZIKV infection in south and southeast of Brazil

BACKGROUND

Zika virus (ZIKV) is an emerging arbovirus associated with foetal malformations and neurological complications. The infection is usually associated with mild symptoms. The comparison between the allelic frequency of polymorphic genes in symptomatic infected individuals in the population can clarify the pathogenic mechanisms of ZIKV. During ZIKV infection, cytokines are produced and natural killer (NK) cells are recruited, whose activation depends on signaling pathways activated by specific receptors, such as killer cell immunoglobulin-like receptors (KIR). These molecules interact with human leukocyte antigen (HLA) class I ligands and are encoded by polymorphic genes.

OBJECTIVES

This study aimed to evaluate the frequency of allelic variants of the genes encoding the KIR receptors and their HLA class I ligands in 139 symptomatic ZIKV-patients and 170 controls negative for the virus, and to evaluate the role of these variants for ZIKV susceptibility.

METHODS

KIR and HLA class I genes were genotyped using the polymerase chain reaction-sequence specific oligonucleotide (PCR-SSO) technique.

FINDINGS

No significant differences in the frequency distribution of KIRs and KIR-HLA in patients compared to controls were observed.

MAIN CONCLUSIONS

KIR and its HLA ligands might play a minor role in ZIKV infection in the south and southeast Brazilian individuals.

A Brief Analysis of Tissue-Resident NK Cells in Pregnancy and Endometrial Diseases: The Importance of Pharmacologic Modulation

NK cells are lymphocytes involved in the innate and adaptative immune response. These cells are located in peripheral blood and tissues with ample functions, from immune vigilant to tolerogenic reactions. In the endometrium, NK cell populations vary depending on age, hormones, and inflammation. When pregnancy occurs, tissue-resident NK cells and conventional NK cells are recruited to protect the fetus, a tolerogenic response. On the contrary, in the inflamed endometrium, various inflammatory cells down-regulate NK tolerance and impair embryo implantation. Therefore, NK cells’ pharmacological modulation is difficult to achieve. Several strategies have been used, from progesterone, lipid emulsions to steroids; the success has not been as expected. However, new therapeutic approaches have been proposed to decrease the endometrial inflammatory burden and increase pregnancy success based on understanding NK cell physiology.

Interaction between HLA-G and NK cell receptor KIR2DL4 orchestrates HER2-positive breast cancer resistance to trastuzumab

Despite the successful use of the humanized monoclonal antibody trastuzumab (Herceptin) in the clinical treatment of human epidermal growth factor receptor 2 (HER2)-overexpressing breast cancer, the frequently occurring drug resistance remains to be overcome. The regulatory mechanisms of trastuzumab-elicited immune response in the tumor microenvironment remain largely uncharacterized. Here, we found that the nonclassical histocompatibility antigen HLA-G desensitizes breast cancer cells to trastuzumab by binding to the natural killer (NK) cell receptor KIR2DL4. Unless engaged by HLA-G, KIR2DL4 promotes antibody-dependent cell-mediated cytotoxicity and forms a regulatory circuit with the interferon-γ (IFN-γ) production pathway, in which IFN-γ upregulates KIR2DL4 via JAK2/STAT1 signaling, and then KIR2DL4 synergizes with the Fcγ receptor to increase IFN-γ secretion by NK cells. Trastuzumab treatment of neoplastic and NK cells leads to aberrant cytokine production characterized by excessive tumor growth factor-β (TGF-β) and IFN-γ, which subsequently reinforce HLA-G/KIR2DL4 signaling. In addition, TGF-β and IFN-γ impair the cytotoxicity of NK cells by upregulating PD-L1 on tumor cells and PD-1 on NK cells. Blockade of HLA-G/KIR2DL4 signaling improved the vulnerability of HER2-positive breast cancer to trastuzumab treatment in vivo. These findings provide novel insights into the mechanisms underlying trastuzumab resistance and demonstrate the applicability of combined HLA-G and PD-L1/PD-1 targeting in the treatment of trastuzumab-resistant breast cancer.

Variations in killer-cell immunoglobulin-like receptor and human leukocyte antigen genes and immunity to malaria

Malaria is one of the deadliest infectious diseases in the world. Immune responses to Plasmodium falciparum malaria vary among individuals and between populations. Human genetic variation in immune system genes is likely to play a role in this heterogeneity. Natural killer (NK) cells produce inflammatory cytokines in response to malaria infection, kill intraerythrocytic Plasmodium falciparum parasites by cytolysis, and participate in the initiation and development of adaptive immune responses to plasmodial infection. These functions are modulated by interactions between killer-cell immunoglobulin-like receptors (KIRs) and human leukocyte antigens (HLAs). Therefore, variations in KIR and HLA genes can have a direct impact on NK cell functions. Understanding the role of KIRs and HLAs in immunity to malaria can help to better characterize antimalarial immune responses. In this review, we summarize the different KIRs and HLAs associated with immunity to malaria thus far.

Reduced Efficacy of Biological Drugs in Psoriatic Patients with HLA-A Bw4-80I KIR Ligands

BACKGROUND

Biological drugs (biologics) are a highly effective therapy for the moderate to severe form of psoriasis, an immune-mediated dermatosis with a strong immunogenetic component. The interaction between human leukocyte antigen (HLA) class I ligands and killer immunoglobulin-like receptors (KIR) has a functional significance in the education of natural killer (NK) cells, and can thus influence the response to biologics.

OBJECTIVE

In this study, we investigated the impact of HLA-A and -B KIR ligands in the response to biologics in a cohort of psoriatic patients.

METHODS

Eighty-five patients with moderate to severe psoriasis treated with biologics (adalimumab, etanercept, infliximab, ustekinumab and secukinumab) were enrolled in the study. Clinical response was evaluated as patients attaining 50%, 75% or 90% reduction in the Psoriasis Area and Severity Index (PASI) (PASI 50, 75 or 90, respectively) over 6 months' follow-up. Poor response was defined as PASI 50, and in this case patients shifted to treatment with a different biologic. Fifty-two patients (61.2%) showed excellent response (PASI 90) to the first biologic, while 33 patients (38.8%), needed two or more biologics before reaching an excellent response (PASI 90) and were considered difficult to treat.

RESULTS

Only HLA-A Bw4-80I ligands were associated with the response to biologics; in particular, they were linked with reduced response both at univariable analysis (odds ratio [OR] 3.11, 95% confidence interval [CI] 1.19-8.07; p = 0.019) and multivariable analysis (OR 5.02, 95% CI 1.40-17.97; p = 0.013).

CONCLUSION

We suggest that the HLA-A Bw4-80I epitope could be a marker of reduced responsiveness to biologics. The possible reason for this is an increase of tumour necrosis factor (TNF)-α and the silencing of NK cells through the predominant interaction with the KIR3DL/S pair. HLA-KIR affinities might lead to a more efficient way to prescribe biologics.

Natural killer cell transcriptional control, subsets, receptors and effector function

There have been considerable advances in characterization of the complexities of natural killer (NK) cell ligand recognition, activation, subsets and effector functions. The nature of the transcription factors that act to define distinctive functional programmes of NK cell subsets are now starting to be clarified as a consequence of studies in knockouts. Importantly, this is being extended to improved understanding of the nature of NK cell memory. As NK cell biology offers increasing resonance with analogous pathways in CD8 biology, some have made the case that immunology may sometimes benefit from a little less conceptual 'splitting' and a little more conceptual 'lumping.'

Decidual Vasculopathy in Preeclampsia and Spiral Artery Remodeling Revisited: Shallow Invasion versus Failure of Involution

Decidual vasculopathy is commonly associated with preeclampsia and develops in the late pregnancy in the uterine spiral arteries, which were previously remodeled by the extravillous trophoblasts. In normal early pregnancy, trophoblasts invade into the spiral artery, leading to vascular transformation, and this transformation is found to be associated with phenotypic switch of the endovascular trophoblasts to express CD56, a maternal protein likely from the natural killer (NK) cells. These endovascular trophoblasts are diminished at term. The decidual vessels are also returned to near normal at the delivery. Both the uterus and the uterine spiral arteries undergo involution after delivery. In preeclampsia, the endovascular trophoblasts are present within the vessel wall associated with the persistence of switched phenotype similar to those seen in the early implantation. The persistence of the endovascular trophoblasts in decidual vasculopathy indicates a failure to return to normal vessels in preeclampsia, thus suggesting a potential mechanism of pathogenesis. NK cells seem critical not only for early implantation and spiral artery remodeling but also for the development of decidual vasculopathy in preeclampsia. In this short review, some critical aspects of decidual vasculopathy in normal pregnancy and preeclampsia are reexamined and a new hypothesis is proposed.

Bioinformatics for immunologists

Immunology was once a specialty prone to cause dismay or even scepticism among outsiders for its struggles to visualize poorly understood, complex interactions through descriptive models integrating cell types, their factors and functions. This was the age of 'too many soft ideas propped up by too little hard data'. Twenty-first century immunologists have the advantage of being able to marry this rich conceptual legacy to a contemporary toolkit offering such depth of hard data across different 'omics' platforms, that they are faced by the opposite dilemma: 'too much hard data to comprehend or synthesize into a meaningful narrative'. Approaches including next-generation sequencing of host and pathogen genomes and transcriptomes, metagenomics of the microbiota, creative strategies for receptor repertoire sequencing, and then for proteomics and metabolomics, encompass all that is needed to tell the entire story, if only we are creative enough, not only to evaluate the message from any given omics platform, but to derive the tools that enable us to integrate the answers from diverse omics platforms in a meaningful way. To achieve this goal, there is an urgent need to ensure we train the next generation of bioinformatically literate researchers.