Killer cell immunoglobulin-like receptors in HLA-B27-associated acute anterior uveitis, with and without axial spondyloarthropathy

Influence of killer immunoglobulin-like receptors genes on the recurrence rate of ocular toxoplasmosis in Brazil

BACKGROUND

Recurrence is a hallmark of ocular toxoplasmosis (OT), and conditions that influence its occurrence remain a challenge. Natural killer cells (NK) are effectors cells whose primary is cytotoxic function against many parasites, including Toxoplasma gondii. Among the NK cell receptors, immunoglobulin-like receptors (KIR) deserve attention due to their high polymorphism.

OBJECTIVES

This study aimed to analyse the influence of KIR gene polymorphism in the course of OT infection and its association with recurrences after an active episode.

METHODS

Ninety-six patients from the Ophthalmologic Clinic of the National Institute of Infectology Evandro Chagas were followed for up to five years. After DNA extraction, genotyping of the patients was performed by polymerase chain reaction sequence-specific oligonucleotide (PCR-SSO) utilising Luminex equipment for reading. During follow-up, 60.4% had a recurrence.

FINDINGS

We identified 25 KIR genotypes and found a higher frequency of genotype 1 (31.7%) with worldwide distribution. We note that the KIR2DL2 inhibitor gene and the gene activator KIR2DS2 were more frequent in patients without recurrence. Additionally, we observed that individuals who carry these genes progressed recurrence episodes slowly compared to individuals who do not carry these genes.

MAIN CONCLUSIONS

The KIR2DL2 and KIR2DS2 are associated as possible protection markers against ocular toxoplasmosis recurrence (OTR).

Association of Killer Cell Immunoglobulin-like Receptor and Human Leukocyte antigen-C Genotype with HLA-B27 Associated Acute Anterior Uveitis and Idiopathic Acute Anterior Uveitis in a Chinese Han Population

Purpose whether killer cell immunoglobulin-like receptors (KIRs) and human leukocyte antigens C (HLA-C) are associated with HLA-B27 associated acute anterior uveitis (B27AAU) and idiopathic AAU (IAAU) remains unclear.Methods PCR with sequence-specific primers was used to analyze KIR genes and HLA-C alleles in a Chinese Han population of 196AAU patients and 210 control subjects.Results The higher frequencies of HLA-C2 and KIR2DL1/HLA-C2 (p = .009 and p = .044, respectively) and the lower frequencies of HLA-C1C1 and HLA-C1 (p = .034 and p = .009, respectively) were observed in B27AAU than control group. The higher frequencies of KIR2DL2 and KIR2DL2/HLA-C1 (p = .009 and p = .044, respectively) and the lower frequencies of KIR2DL3 and KIR2DL3/HLA-C1 (p = .000 and p = .001, respectively) were observed in IAAU than control group.Conclusions HLA-C2 and KIR2DL1/HLA-C2, KIR2DL2, and KIR2DL2/HLA-C1 might be susceptible for B27AAU and IAAU, respectively. HLA-C1C1 and HLA-C1, KIR2DL3 and KIR2DL3/HLA-C1 might protect from B27AAU and IAAU, respectively.

Uveitis in spondyloarthritis

Uveitis is the most frequent extra-articular manifestation of axial spondyloarthritis (SpA), occurring in up to one-third of the patients. In the majority of patients, uveitis is acute, anterior and unilateral and presents with photosensitivity, sudden onset of pain and blurred vision. Topical steroids are an effective treatment; however, recurrent or refractory cases may need conventional disease-modifying antirheumatic drugs or biological treatment with monoclonal tumor necrosis factor (TNF) inhibitors, thus also influencing treatment strategy of the underlying SpA. Though the exact pathogenesis of SpA and uveitis remains unknown, both seem to result from the interaction of a specific, mostly shared genetical background (among other HLA-B27 positivity), external influences such as microbiome, bacterial infection or mechanical stress and activation of the immune system resulting in inflammation. Up to 40% of patients presenting with acute anterior uveitis (AAU) have an undiagnosed SpA. Therefore, an effective referral strategy for AAU patients is needed to shorten the diagnostic delay of SpA and enable an early effective treatment. Further, the risk for ophthalmological manifestations increases with the disease duration in SpA; and patients presenting with ocular symptoms should be referred to an ophthalmologist. Thus, a close collaboration between patient, rheumatologist and ophthalmologist is needed to optimally manage ocular inflammation in SpA.

Ocular toxoplasmosis: susceptibility in respect to the genes encoding the KIR receptors and their HLA class I ligands

The objective of this study was to investigate the influence of the genes encoding the KIR receptors and their HLA ligands in the susceptibility of ocular toxoplasmosis. A total of 297 patients serologically-diagnosed with toxoplasmosis were selected and stratified according to the presence (n = 148) or absence (n = 149) of ocular scars/lesions due to toxoplasmosis. The group of patients with scars/lesions was further subdivided into two groups according to the type of ocular manifestation observed: primary (n = 120) or recurrent (n = 28). Genotyping was performed by PCR-SSOP. Statistical analyses were conducted using the Chi-square test, and odds ratio with a 95% confidence interval was also calculated to evaluate the risk association. The activating KIR3DS1 gene was associated with increased susceptibility for ocular toxoplasmosis. The activating KIR together with their HLA ligands (KIR3DS1-Bw4-80Ile and KIR2DS1⁺/C2⁺⁺ KIR3DS1⁺/Bw4-80Ile⁺) were associated with increased susceptibility for ocular toxoplasmosis and its clinical manifestations. KIR-HLA inhibitory pairs -KIR2DL3/2DL3-C1/C1 and KIR2DL3/2DL3-C1- were associated with decreased susceptibility for ocular toxoplasmosis and its clinical forms, while the KIR3DS1⁻/KIR3DL1⁺/Bw4-80Ile⁺ combination was associated as a protective factor against the development of ocular toxoplasmosis and, in particular, against recurrent manifestations. Our data demonstrate that activating and inhibitory KIR genes may influence the development of ocular toxoplasmosis.

HLA-B27 Anterior Uveitis: Immunology and Immunopathology

Acute anterior uveitis (AAU) is the commonest type of uveitis and HLA-B27 AAU is the most frequently recognized type of acute anterior uveitis and anterior uveitis overall. Recent evidence indicates that acute anterior uveitis is a heterogenous disease, is polygenic and is frequently associated with the spondyloarthropathies (SpA). Studies of patients with AAU and animal models of disease indicate a role for innate immunity, the IL-23 cytokine pathway and exogenous factors, in the pathogenesis of both SpA and acute anterior uveitis. Recently described genetic associations cluster around immunologic pathways, including the IL-17 and IL-23 pathways, antigen processing and presentation, and lymphocyte development and activation. Patients with ankylosing spondylitis (AS) and AAU share other genetic markers, such as ERAP-1, which show strong evidence of gene-gene interaction and point to new mechanisms of disease pathogenesis. These observations have major implications for understanding the pathogenesis of HLA-B27 diseases, such as AAU, and may lead to the development of more specific therapy for AAU. Received 6 January 2016; revised 6 February 2016; accepted 18 February 2016; published online 31 May 2016.

Genetic dissection of acute anterior uveitis reveals similarities and differences in associations observed with ankylosing spondylitis

OBJECTIVE

To use high-density genotyping to investigate the genetic associations of acute anterior uveitis (AAU) in patients with and those without ankylosing spondylitis (AS).

METHODS

We genotyped samples from 1,711 patients with AAU (either primary or combined with AS), 2,339 AS patients without AAU, and 10,000 control subjects on an Illumina Immunochip Infinium microarray. We also used data for AS patients from previous genome-wide association studies to investigate the AS risk locus ANTXR2 for its putative effect in AAU. ANTXR2 expression in mouse eyes was investigated by real-time quantitative reverse transcription-polymerase chain reaction.

RESULTS

A comparison between all patients with AAU and healthy control subjects showed strong association over HLA-B, corresponding to the HLA-B27 tag single-nucleotide polymorphism rs116488202. The association of 3 non-major histocompatibility complex loci, IL23R, the intergenic region 2p15, and ERAP1, reached genome-wide significance (P < 5 × 10(-8)). Five loci harboring the immune-related genes IL10-IL19, IL18R1-IL1R1, IL6R, the chromosome 1q32 locus harboring KIF21B, as well as the eye-related gene EYS, were also associated, reaching a suggestive level of significance (P < 5 × 10(-6)). Several previously confirmed AS associations demonstrated significant differences in effect size between AS patients with AAU and AS patients without AAU. ANTXR2 expression varied across eye compartments.

CONCLUSION

These findings of both novel AAU-specific associations and associations shared with AS demonstrate overlapping but also distinct genetic susceptibility loci for AAU and AS. The associations in IL10 and IL18R1 are shared with inflammatory bowel disease, suggesting common etiologic pathways.

Diversity of killer cell immunoglobulin-like receptor genes in uveitis associated with autoimmune diseases: ankylosing spondylitis and Behçet disease

PURPOSE

To determine whether the frequencies of specific killer cell immunoglobulin-like receptors (KIR) genotypes are associated with the incidence of uveitis in ankylosing spondylitis (AS) and Behçet disease (BD).

METHODS

The authors analyzed the frequency of 16 KIR genes in Koreans with either AS (110 patients, all HLA-B27-positive) or BD (86 patients), using polymerase chain reaction sequence-specific oligonucleotide probing.

RESULTS

The frequency of the inhibitory receptor KIR3DL1 was lower in AS patients affected by uveitis than that in the general population (p < 0.05). The frequency of the KIR3DL1(-)/2DS3(-) was significantly higher in AS patients with uveitis (odds ratio = 9.306, p = 0.007).

CONCLUSIONS

The study suggests that KIR3DL1 might associate with the resistance to AS-associated uveitis by influencing natural killer cell activity.

Genetics of ankylosing spondylitis

Ankylosing spondylitis (AS) is a chronic inflammatory arthritis that affects the spine and sacroiliac joints. It causes significant disability and is associated with a number of other features including peripheral arthritis, anterior uveitis, psoriasis and inflammatory bowel disease (IBD). Significant progress has been made in the genetics of AS have in the last five years, leading to new treatments in trial, and major leaps in understanding of the aetiopathogenesis of the disease.

Human diversity of killer cell immunoglobulin-like receptors and disease

Natural Killer (NK) cells are the third population of lymphocyte in the mononuclear cell compartment that triggers first-line of defense against viral infection and tumor transformation. Historically, NK cells were thought of as components of innate immunity based on their intrinsic ability to spontaneously kill target cells independent of HLA antigen restriction. However, it is now clear that NK cells are quite sophisticated and use a highly specific and complex target cell recognition receptor system arbitrated via a multitude of inhibitory and activating receptors. Killer cell immunoglobulin-like receptors (KIR) are the key receptors of human NK cells development and function. To date, fourteen distinct KIRs have been identified: eight are inhibitory types, and six are activating types. The number and type of KIR genes present varies substantially between individuals. Inhibitory KIRs recognize distinct motifs of polymorphic HLA class I molecules. Upon engagement of their specific HLA class I ligands, inhibitory KIR dampen NK cell reactivity. In contrast, activating KIRs are believed to stimulate NK cell reactivity when they sense their ligands (unknown). KIR and HLA gene families map to different human chromosomes (19 and 6, respectively), and their independent segregation produces a wide diversity in the number and type of inherited KIR-HLA combinations, likely contributing to overall immune competency. Consistent with this hypothesis, certain combinations of KIR-HLA variants have been correlated with susceptibility to diseases as diverse as autoimmunity, viral infections, and cancer. This review summarizes our emerging understanding of KIR-HLA diversity in human health and disease.

An update on the genetics of HLA B27-associated acute anterior uveitis

The discovery of the association of HLA B27 with spondyloarthropathy led to more questions than answers about the role of this gene in disease susceptibility. The realization that HLA B27 was not responsible for all of the genetic effects helped to lay a foundation for further investigation into the genetics of uveitis. Over several decades, genetic findings have provided clues to advance the understanding of mechanisms of uveitis and to catalyze new research on diagnostics, animal models, and therapies. From the early candidate gene studies on immune mediators to the recent genome-wide investigations, much has been discovered. However, these discoveries have come with the caveat that a genetic finding does not automatically reveal the disease-relevant functional effect of the associated variant.

The Genetic Basis of Spondyloarthritis: SPARTAN/IGAS 2009

A joint meeting was held in July 2009 in Houston, Texas, of members of the Spondyloarthritis Research and Therapy Network (SPARTAN), founded in 2003 to promote research, education, and treatment of ankylosing spondylitis (AS) and related forms of spondyloarthritis (SpA), and members of International Genetics of AS (IGAS), founded in 2003 to encourage and coordinate studies internationally in the genetics of AS. The general topic was the genetic basis of SpA, with presentations on the future of human genetic studies; microbes, SpA, and innate immunity; susceptibility of AS to the major histocompatibility complex (MHC) and non-MHC; and individual discussions of the genetics of psoriasis and psoriatic arthritis, uveitis, inflammatory bowel disease, and enteropathic arthritis. Summaries of those discussions are presented.