Association of MICA-129 polymorphism and circulating soluble MICA level with rheumatoid arthritis in a south Indian Tamil population

Functional MICA Variants Are Differentially Associated with Immune-Mediated Inflammatory Diseases

As the principal ligand for NKG2D, MICA elicits the recruitment of subsets of T cells and NK cells in innate immunity. MICA gene variants greatly impact the functionality and expression of MICA in humans. The current study evaluated whether MICA polymorphisms distinctively influence the pathogenesis of psoriasis (PSO), rheumatoid arthritis (RA), and systemic lupus erythematosus (SLE) in Taiwanese subjects. The distributions of MICA alleles and levels of serum soluble NKG2D were compared between healthy controls and patients with PSO, RA, and SLE, respectively. The binding capacities and cell surface densities of MICA alleles were assessed by utilizing stable cell lines expressing four prominent Taiwanese MICA alleles. Our data revealed that MICA*010 was significantly associated with risks for PSO and RA (PFDR = 1.93 × 10-15 and 0.00112, respectively), while MICA*045 was significantly associated with predisposition to SLE (PFDR = 0.0002). On the other hand, MICA*002 was associated with protection against RA development (PFDR = 4.16 × 10-6), while MICA*009 was associated with a low risk for PSO (PFDR = 0.0058). MICA*002 exhibited the highest binding affinity for NKG2D compared to the other MICA alleles. Serum concentrations of soluble MICA were significantly elevated in SLE patients compared to healthy controls (p = 0.01). The lack of cell surface expression of the MICA*010 was caused by its entrapment in the endoplasmic reticulum. As a prevalent risk factor for PSO and RA, MICA*010 is deficient in cell surface expression and is unable to interact with NKG2D. Our study suggests that MICA alleles distinctively contribute to the pathogenesis of PSO, RA, and SLE in Taiwanese people.

The Role of NKG2D and Its Ligands in Autoimmune Diseases: New Targets for Immunotherapy

Natural killer (NK) cells and CD8+ T cells can clear infected and transformed cells and generate tolerance to themselves, which also prevents autoimmune diseases. Natural killer group 2 member D (NKG2D) is an important activating immune receptor that is expressed on NK cells, CD8+ T cells, γδ T cells, and a very small percentage of CD4+ T cells. In contrast, the NKG2D ligand (NKG2D-L) is generally not expressed on normal cells but is overexpressed under stress. Thus, the inappropriate expression of NKG2D-L leads to the activation of self-reactive effector cells, which can trigger or exacerbate autoimmunity. In this review, we discuss the role of NKG2D and NKG2D-L in systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), multiple sclerosis (MS), type I diabetes (T1DM), inflammatory bowel disease (IBD), and celiac disease (CeD). The data suggest that NKG2D and NKG2D-L play a pathogenic role in some autoimmune diseases. Therefore, the development of strategies to block the interaction of NKG2D and NKG2D-L may have therapeutic effects in some autoimmune diseases.

NKG2D receptor regulates CD4+T cell differentiation via interaction with dendritic cells in patients with juvenile idiopathic arthritis

NKG2D provides a costimulatory signal for activation of CD4+ T cells. We explored its role in interactions of CD4+ T cells and dendritic cells (DCs) in juvenile idiopathic arthritis (JIA) patients by using NKG2D genetically modified CD4+ T cells. We found active JIA patients had significantly higher content of CD4 + NKG2D+ T cells than healthy controls. Expression of NKG2D on CD4+ T cells, and MICA and MICB on DCs were significantly greater in articular JIA than systemic JIA. NKG2D induced IL- 12 and suppressed IL-10 and TGF-β from CD4+ T cells, increased IFN-γ + CD4+ T and IL-17+ CD4+ T cells, RORc and T-bet, but reduced CD25+ Foxp3+ CD4+ T cells, IL-4+ CD4+ T cells, Foxp3, and GATA3 in JIA patients. NKG2D decreased IL-10 and increased CD83, MICA, and MICB of DCs in JIA and controls. So NKG2D regulates differentiation of CD4+ T cells directly and the maturation of DCs indirectly.

Association of MICA gene Exon-5 polymorphism in oral submucous fibrosis

OBJECTIVE

The present study was conducted to explore the allele frequencies of MICA gene Exon-5 transmembrane and to measure the circulatory MICA levels in various histologic grades of patients with oral submucous fibrosis (OSF) compared to healthy individuals.

STUDY DESIGN

We enrolled a total of 595 patients for this cross-sectional study and divided them into 2 groups: healthy controls (n = 320) and patients with OSF (n = 275). Further, patients with OSF were subdivided based on their histologic gradings. The genomic DNA was extracted followed by a polymerase chain reaction and genotyping using the ABI Prism DNA Sequencer (ThermoFisher Scientific, Inc., Waltham, MA, USA).

RESULTS

Our study showed that the A5 allele of the MICA gene in the Exon-5 region conferred significant risk for patients with OSF. With reference to the histologic gradings of OSF, we found that the MICA gene conferred statistically significant risk among patients with grade III OSF. On the other hand, the A8 allele of MICA gene in the Exon-5 region conferred significant protection among the overall OSF cohort and in the grade III of histologic grade. Finally, the circulatory human MICA levels were found to have a stepwise increase from grade I toward grade III in patients with OSF.

CONCLUSION

Our results suggested that the A5 allele in MICA might confer risk for the progression of OSF among the South Indian ethnic population.

Diseases association with the polymorphic major histocompatibility complex class I related chain a: MICA gene

The Major Histocompatibility Complex class I chain-related molecule A (MICA) genes encode a highly polymorphic glycoprotein among the cell surface antigens that trigger an immune response after allograft transplantation. It is encoded by the MICA gene, a member of the glycosylated MIC genes. Discovered in 1994, the MICA gene is located within the MHC class I region. Moreover, its biological function is achieved through the interaction with the NKG2D receptor. Unlike the classical HLA molecules, MICA protein is not associated with β2- microglobulin nor binds peptides. MICA gene expression may result in a cytotoxic response and IFN-γ secretion through the up-regulation by heat shock proteins in response to infection (Human Cytomegalovirus HCMV), mediated by NKG2D-expressing cells. Anti-MICA antibodies were identified as significant risk factors for antibody mediated rejection after being detected in sera of patients with graft rejection. In addition, soluble MICA proteins (sMICA) has been detected in the serum of transplant recipients with cancers. Furthermore, the association of MICA polymorphisms with infectious diseases, various autoimmune diseases, cancer, and allograft rejection or graft-versus-host disease (GVHD) has been studied. Moreover, numerous advanced disease studies centered on MICA polymorphism are independent of HLA association. In this review, we discussed the up-to-date data about MICA and the association of MICA polymorphism with infections, autoimmune diseases, graft-versus-host disease, and cancer.

MICA*019 Allele and Soluble MICA as Biomarkers for Ankylosing Spondylitis in Taiwanese

MICA (major histocompatibility complex class I chain-related gene A) interacts with NKG2D on immune cells to regulate host immune responses. We aimed to determine whether MICA alleles are associated with AS susceptibility in Taiwanese. MICA alleles were determined through haplotype analyses of major MICA coding SNP (cSNP) data from 895 AS patients and 896 normal healthy controls in Taiwan. The distributions of MICA alleles were compared between AS patients and normal healthy controls and among AS patients, stratified by clinical characteristics. ELISA was used to determine soluble MICA (sMICA) levels in serum of AS patients and healthy controls. Stable cell lines expressing four major MICA alleles (MICA*002, MICA*008, MICA*010 and MICA*019) in Taiwanese were used for biological analyses. We found that MICA*019 is the only major MICA allele significantly associated with AS susceptibility (P_FDR = 2.25 × 10⁻¹¹⁵; OR, 14.90; 95% CI, 11.83–18.77) in Taiwanese. In addition, the MICA*019 allele is associated with syndesmophyte formation (P_FDR = 0.0017; OR, 1.69; 95% CI, 1.29–2.22) and HLA-B27 positivity (P_FDR = 1.45 × 10⁻³³; OR, 28.79; 95% CI, 16.83–49.26) in AS patients. Serum sMICA levels were significantly increased in AS patients as compared to healthy controls. Additionally, MICA*019 homozygous subjects produced the highest levels of sMICA, compared to donors with other genotypes. Furthermore, in vitro experiments revealed that cells expressing MICA*019 produced the highest level of sMICA, as compared to other major MICA alleles. In summary, the MICA*019 allele, producing the highest levels of sMICA, is a significant risk factor for AS and syndesmophyte formation in Taiwanese. Our data indicate that a high level of sMICA is a biomarker for AS.

Soluble MICA and anti-MICA Antibodies as Biomarkers of Nasopharyngeal Carcinoma Disease

The MHC class I chain-related molecule A (MICA) is a ligand for the activating natural killer (NK) cell receptor NKG2D. A part from its genetic diversity, MICA is characterized by the presence of membrane-bound and soluble isoform (sMICA) and by the propensity to elicit antibody-mediated allogeneicity (MICA Abs). Altogether such properties are important in the cancer setting. Here, we investigated whether MICA polymorphism, serum level of sMICA and MICA antibodies (Abs) may influence nasopharyngeal carcinoma (NPC) risk. 274 NPC naïve of treatment patients and 275 healthy individuals, all originating from Tunisia were included and genotyped. Among them, 160 sera from patients and 51 from controls were analyzed for the sMICA level by ELISA and were tested for the presence of MICA Abs by Luminex assay. The statistical analysis showed that: (1) we extend and confer our previous finding concerning Val/Val association with risk of NPC (p = .02, OR = 1.56; 95%CI [1.12-2.11]). (2) The higher level of sMICA characterized patients advanced stage of the disease. (3) The 18 (78%) of patients having MICA Abs exhibit all a non-advanced stage of the tumor extension at presentation. MICA129 Met /Val, sMICA and MICA Abs could be potential biomarkers of prediction, the diverse staging of NPC and hence prognostic and treatment.