A typing system for the major histocompatibility complex class I chain related genes A and B using polymerase chain reaction with sequence-specific primers

MICA and MICB allele assortment in Finland

Genetic variation in the MICA and MICB genes located within the major histocompatibility complex region has been reported to be associated with transplantation outcome and susceptibility to autoimmune diseases and infections. Only limited data of polymorphism in these genes in different populations are available. We here report allelic variation at 2-field resolution and the haplotypes of the MICA and MICB genes in Finland (n = 1032 individuals), a north European population with historical bottleneck and founder effects. Altogether 24 MICA and 18 MICB alleles were found, forming 70 estimated MICA-MICB haplotypes. As compared to other populations frequency differences were found, for example, MICA*010:01 was found to be at an allele frequency of 0.133 in Finland which is higher than in other European populations (0.021-0.077), but close to Asian populations (0.151-0.220). Three novel alleles with amino acid change are described. The results demonstrate a relatively high level of polymorphism and population differences in MICA and MICB allele distribution.

Positive association between MIC gene polymorphism and tuberculosis in Chinese population

The disease progression and morbidity of tuberculosis (TB) infections are determined by virulence of the micro-organism, host genetic factors and environmental factors. The highly polymorphic MHC class I chain-related gene (MIC) could serve as a potential host genetic candidate. To investigate the association of MIC polymorphism with TB infection, 124 patients and 191 ethnically matched controls from Hunan province, Southern China, were genotyped for the MIC polymorphism using polymerase chain reaction-sequence specific priming and sequencing-based typing. The results showed that allele frequencies of MIC-sequence and MICA-STR were different in TB patients in comparison to normal controls (both P < 0.05). MICA-A4 and MICA*012:01 alleles were positive associated (OR = 2.42, 95% CI: 1.69-3.87; OR = 3.41, 95% CI: 2.19-5.33, respectively, both P_c < 0.05) while MICA -A5 were inversely associated (OR = 0.59, 95%CI: 0.41-0.94, P_c < 0.05) with TB. Homozygote MICA*012:01/012:01 was observed to have significant risk effects on TB (OR = 4.76, 95% CI: 1.94-11.69, P_c0000-0001-5151-1853 < 0.05). Additionally, MICB*008 allele conduct a significant risk effect for TB (OR = 3.17, 95%CI: 1.80-5.61, P_c < 0.05). All the data showed that MIC polymorphism was associated with the variable susceptibility to TB in Chinese population.

Genetic polymorphism analysis of MICB gene in Jing ethnic minority of Southern China

In the present study, the polymorphism in the 5'-upstream regulation region (5'-URR), coding region (exons 2-4), and the 3'-untranslated region (3'-UTR) of MICB gene were investigated for 150 healthy unrelated Jing individuals in Guangxi Zhuang Autonomous Region, by using PCR-SBT method. A total of 14 variation sites in the 5'-URR, 9 in coding region, and 6 in the 3'-UTR were detected in the Jing population. The MICB gene seems to present two different lineages showing functional variations mainly in nucleotides of the promoter region. Nineteen different MICB extended haplotypes (EHs) encompassing the 5'-URR, exons 2-4, and 3'-UTR were found in this population, and the most frequent was EH2 (20.33%). The findings here are of importance for future studies on the potential role of regulation region of MICB gene in disease association, transplantation, viral infection, and tumor progression among Jing population.

MICB*002 and MICB*014 protect against rheumatoid arthritis, whereas MICA*009 and MICA*A6 are associated with rheumatoid arthritis in a Hainan Han Chinese population

AIM

Rheumatoid arthritis (RA) as an inflammatory autoimmune disease affects the synovial joints as well as other organs and tissues. Since aberrant expression of MIC molecules has been observed in RA patient, MIC genotypes might play certain roles in the development of RA.

METHOD

To explore the association of MICA and MICB polymorphisms with RA in a Han Chinese population in Hainan Island, samples from 172 RA and 137 healthy controls were genotyped for MICA and MICB.

RESULTS

Our results indicated that MICB*002 and MICB*014 were less frequent in RA patients than in controls (P = 0.000, 0.005) while there were higher percentages of RA patients carrying MICA*009 and MICA*A6 (P = 0.005).

CONCLUSION

Different MIC variants might modulate the autoimmune reaction differently in RA disease and therefore serve as protective or risk factors.

The association between MICA/MICB polymorphism and respiratory syncytial virus infection in children

MICA/MICB gene polymorphisms are related to several cancers and infectious diseases, but there are no reports on the association between MICA/MICB gene polymorphisms and respiratory syncytial virus (RSV) infection. To clarify the association between MICA/MICB gene polymorphisms and infection of RSV in children, we collected fresh blood samples from paediatric patients with and without pneumonia after RSV infection. The MICA/MICB alleles were characterized by PCR sequence-specific primers (PCR-SSP) and PCR sequence-based genotyping (PCR-SBT), and then, the frequency of the MICA/MICB alleles and haplotypes was calculated. The results showed that the frequencies of MICA*002:01 and MICA-A9 in RSV-infected patients were significantly lower than in controls (9% vs. 20%, pc = 0.04). The allele frequency of MICA*002:01 in pneumonia patients (8%) and nonpneumonia patients (9%) was significantly lower than in controls (20%, pc = 0.02). MICA*002:01-MICB*008(Δrel = 0.616), MICA*009-MICB*016 (Δrel = 0.506), and MICA*045-MICB*014 (Δrel = 0.700) showed linkage disequilibrium in patients infected with RSV. The haplotype frequency of MICA*002:01-MICB*005:02 in RSV-infected patients was significantly lower than in controls (10% vs. 16%, pc = 0.033). In conclusion, allele MICA*002:01/A9 and haplotype MICA*002:01-MICB*005:02 were negatively associated with RSV respiratory tract infections.

Immune Responses to Tissue-Restricted Nonmajor Histocompatibility Complex Antigens in Allograft Rejection

Chronic diseases that result in end-stage organ damage cause inflammation, which can reveal sequestered self-antigens (SAgs) in that organ and trigger autoimmunity. The thymus gland deletes self-reactive T-cells against ubiquitously expressed SAgs, while regulatory mechanisms in the periphery control immune responses to tissue-restricted SAgs. It is now established that T-cells reactive to SAgs present in certain organs (e.g., lungs, pancreas, and intestine) are incompletely eliminated, and the dysregulation of peripheral immuneregulation can generate immune responses to SAgs. Therefore, chronic diseases can activate self-reactive lymphocytes, inducing tissue-restricted autoimmunity. During organ transplantation, donor lymphocytes are tested against recipient serum (i.e., cross-matching) to detect antibodies (Abs) against donor human leukocyte antigens, which has been shown to reduce Ab-mediated hyperacute rejection. However, primary allograft dysfunction and rejection still occur frequently. Because donor lymphocytes do not express tissue-restricted SAgs, preexisting Abs against SAgs are undetectable during conventional cross-matching. Preexisting and de novo immune responses to tissue-restricted SAgs (i.e., autoimmunity) play a major role in rejection. In this review, we discuss the evidence that supports autoimmunity as a contributor to rejection. Testing for preexisting and de novo immune responses to tissue-restricted SAgs and treatment based on immune responses after organ transplantation may improve short- and long-term outcomes after transplantation.

Genetics, genomics, and evolutionary biology of NKG2D ligands

Human and mouse NKG2D ligands (NKG2DLs) are absent or only poorly expressed by most normal cells but are upregulated by cell stress, hence, alerting the immune system in case of malignancy or infection. Although these ligands are numerous and highly variable (at genetic, genomic, structural, and biochemical levels), they all belong to the major histocompatibility complex class I gene superfamily and bind to a single, invariant, receptor: NKG2D. NKG2D (CD314) is an activating receptor expressed on NK cells and subsets of T cells that have a key role in the recognition and lysis of infected and tumor cells. Here, we review the molecular diversity of NKG2DLs, discuss the increasing appreciation of their roles in a variety of medical conditions, and propose several explanations for the evolutionary force(s) that seem to drive the multiplicity and diversity of NKG2DLs while maintaining their interaction with a single invariant receptor.

MICA/B genotyping of Tujias from Zhangjiajie, Hunan Province, China

One hundred eighty-seven Tujia individuals from Zhangjiajie, Hunan Province, China were genotyped at the MICA and MICB loci using polymerase chain reaction-sequence specific priming and sequencing-based typing methods. MICA and MCB genotypes are consistent with expected HW proportions. These genotype data are available in the Allele Frequencies Net Database.

MICB Allele Genotyping on Microarrays by Improving the Specificity of Extension Primers

Major histocompatibility complex (MHC) class I chain-related gene B (MICB) encodes a ligand for activating NKG2D that expressed in natural killer cells, γδ T cells, and αβ CD8⁺ T cells, which is associated with autoimmune diseases, cancer, and infectious diseases. Here, we have established a system for genotyping MICB alleles using allele-specific primer extension (ASPE) on microarrays. Thirty-six high quality, allele-specific extension primers were evaluated using strict and reliable cut-off values using mean fluorescence intensity (MFI), whereby an MFI >30,000 represented a positive signal and an MFI <10,000 represented a negative signal. Eight allele-specific extension primers were found to be false positives, five of which were improved by adjusting their length, and three of which were optimized by refractory modification. The MICB alleles (*002:01, *003, *005:02/*010, *005:03, *008, *009N, *018, and *024) present in the quality control panel could be exactly defined by 22 allele-specific extension primers. MICB genotypes that were identified by ASPE on microarrays were in full concordance with those identified by PCR-sequence-based typing. In conclusion, we have developed a method for genotyping MICB alleles using ASPE on microarrays; which can be applicable for large-scale single nucleotide polymorphism typing studies of population and disease associations.

MIC gene polymorphism and haplotype diversity in Zhuang nationality of Southern China

Zhuang ethnic minority is the largest minority group in China. Here, we report for the first time the polymorphisms of MICA and MICB in a healthy Zhuang population of 209 unrelated individuals. Using polymerase chain reaction-sequence specific priming (PCR-SSP) and sequencing-based typing (PCR-SBT), 13 MICA-sequence alleles and 5 MICA-STR alleles, as well as 11 MICB alleles were detected, among which MICA(∗)010, MICA(∗)A5 and MICB(∗)005:02 were the most frequent alleles. Linkage disequilibria was investigated and the most common two-locus haplotypes were MICB(∗)005:02-MICA(∗)010 and MICB(∗)014-MICA(∗)045. These results suggest informative genetic markers for investigating origins and evolution of MHC class I region haplotypes in Zhuang population.

Role of antibodies to self-antigens in chronic allograft rejection: potential mechanism and therapeutic implications

Significant progress has been made in preventing acute allograft rejection following solid organ transplantation resulting in improved allograft survival. However, long term function still remains disappointing primarily due to chronic allograft rejection. Alloimmune responses primarily defined by the development of antibodies (Abs) to donor mismatched major histocompatibility antigens during the post-transplantation period have been strongly correlated to the development of chronic rejection. In addition, recent studies have demonstrated an important role for autoimmunity including the development of Abs to organ specific self-antigens in the pathogenesis of chronic allograft rejection. Based on this, a new paradigm has evolved indicating a possible cross-talk between the alloimmune responses and autoimmunity leading to chronic rejection. In this review, we will discuss the emerging concept for the role of cellular and humoral immune responses to self-antigens in the immunopathogenesis of chronic allograft rejection which has the potential to develop new strategies for the prevention and/or treatment of chronic rejection.

Association of MICA gene polymorphisms with liver fibrosis in schistosomiasis patients in the Dongting Lake region

Major histocompatibility complex class I chain-related A (MICA) is a highly polymorphic gene located within the MHC class I region of the human genome. Expressed as a cell surface glycoprotein, MICA modulates immune surveillance by binding to its cognate receptor on natural killer cells, NKG2D, and its genetic polymorphisms have been recently associated with susceptibility to some infectious diseases. We determined whether MICA polymorphisms were associated with the high rate of Schistosoma parasitic worm infection or severity of disease outcome in the Dongting Lake region of Hunan Province, China. Polymerase chain reaction-sequence specific priming (PCR-SSP) and sequencing-based typing (SBT) were applied for high-resolution allele typing of schistosomiasis cases (N = 103, age range = 36.2-80.5 years, 64 males and 39 females) and healthy controls (N = 141, age range = 28.6-73.3 years, 73 males and 68 females). Fourteen MICA alleles and five short-tandem repeat (STR) alleles were identified among the two populations. Three (MICA*012:01/02, MICA*017 and MICA*027) showed a higher frequency in healthy controls than in schistosomiasis patients, but the difference was not significantly correlated with susceptibility to S. japonicum infection (Pc > 0.05). In contrast, higher MICA*A5 allele frequency was significantly correlated with advanced liver fibrosis (Pc < 0.05). Furthermore, the distribution profile of MICA alleles in this Hunan Han population was significantly different from those published for Korean, Thai, American-Caucasian, and Afro-American populations (P < 0.01), but similar to other Han populations within China (P > 0.05). This study provides the initial evidence that MICA genetic polymorphisms may underlie the severity of liver fibrosis occurring in schistosomiasis patients from the Dongting Lake region.

Association of MICA Alleles with Autoimmune Thyroid Disease in Korean Children

Background. Major histocompatibility complex class I chain-related gene A (MICA) is a ligand for the activating NKG2D receptor expressed on natural killer (NK) cells. We aimed to assess the association of MICA polymorphism with autoimmune thyroid disease (AITD) in Korean children. Methods. Eighty-one patients with AITD were recruited. We analyzed MICA polymorphisms by PCR-SSP and compared the results with those of 70 healthy controls. Results. In AITD, the allele frequencies of MICA∗010 (OR = 2.21; 95% CI, 1.30-3.76, P < 0.003, P(c) < 0.042) were higher than those of controls. Patients who did not have thyroid-associated ophthalmopathy showed higher frequencies of MICA∗010 (OR = 2.99; 95% CI, 1.47-6.08, P < 0.003, P(c) < 0.042) and lower frequencies of MICA∗008 (OR = 0.08; 95% CI, 0.01-0.62, P < 0.001, P(c) < 0.014) compared to those of controls. HLA-B∗46, which shows the strongest association with AITD compared with other HLA alleles, showed the strongest linkage disequilibrium with MICA∗010. Analyses of the associations between MICA∗010 and HLA-B∗46 with AITD suggest an association of the MICA allele with AITD. Conclusions. Our results suggest that innate immunity might contribute to the pathogenesis of AITD.

Development of antibodies to human leukocyte antigen precedes development of antibodies to major histocompatibility class I-related chain A and are significantly associated with development of chronic rejection after human lung transplantation

The development of antibodies (Abs) to major histocompatibility (MHC) class I-related chain A (MICA) and human leukocyte antigen (HLA) and their role in the immunopathogenesis of chronic rejection (bronchiolitis obliterans syndrome [BOS]) after human lung transplantation (LTx) was analyzed. Sera from 80 LTx recipients were analyzed for anti-MICA and anti-HLA Abs using Luminex and flow PRA (panel reactive assay). Development of Abs either to MICA alone or MICA and HLA together significantly correlated (p < 0.01) with development of BOS. Kinetic analysis in the post-LTx period revealed that development of anti-HLA Abs (7.6 +/- 4.7 months) preceded the development of anti-MICA Abs (10.0 +/- 3.5 months). Abs to MICA alleles (*001 and *009) developed approximately 6 months after LTx and peak titers were present at the time of clinical diagnosis of BOS (16.3 +/- 2.7 months). The development of Abs to both MICA and HLA was strongly associated with the development of BOS thereby suggesting a synergistic effect. Furthermore, immune response to mismatched HLA can lead to development of Abs to other MHC related antigens expressed on the airway epithelial cells. Cumulatively, these immune responses contribute to the pathogenesis of chronic rejection following human LTx.

The relationship of anti-MICA antibodies and MICA expression with heart allograft rejection

The role of MICA antibodies in acute heart allograft rejection was examined utilizing 190 pre- and post-transplant serum samples from 44 patients collected during the first year after transplantation. MICA antibodies were detected by CDC test on recombinant cell lines and by the newly developed Luminex MICA antibody detection assay. Additionally, MICA expression was analyzed by 'real time' RT-PCR and by immunohistochemistry in 10 endomyocardial biopsies. Only two subjects had HLA antibodies post-transplant. Nevertheless, MICA antibodies were found in a significant number of subjects. The prevalence of MICA antibodies was significantly higher among those with severe acute rejection (AR) than in those without rejection (60.7% vs. 14.3%, p = 0.0038 by CDC; 55.5% vs. 5.7%, p = 0.0020 by Luminex). In most cases, the appearance of MICA antibodies post-transplant precedes AR. Following transplantation, MICA up-regulation correlated with histological evidence of severe rejection. Monitoring for MICA antibodies post-transplant may be useful to establish new risk factors for acute rejection.

Conserved extended haplotypes of the major histocompatibility complex: further characterization

Since the complete sequencing of a human major histocompatibility complex (MHC) haplotype, interest in non-human leucocyte antigen (HLA) genes encoded in the MHC has been growing. Non-HLA genes, which outnumber the HLA genes, may contribute to or account for HLA and disease associations. Most information on non-HLA genes has been obtained in separate studies of individual loci. To comprehensively address polymorphisms of relevant non-HLA genes in 'conserved extended haplotypes' (CEH), we investigated 101 International Histocompatibility Workshop reference cell lines and nine additional anonymous samples representing all 37 unambiguously characterized CEHs at MICA, NFKBIL1, LTA, NCR3, AIF1, HSPA1A, HSPA1B, BF, NOTCH4 and a single nucleotide polymorphism (SNP) at HLA-DQA1 as well as MICA, NOTCH4, HSPA1B and all five tumour necrosis factor short tandem repeat (STR) polymorphisms. This work (1) provides an extensive catalogue of MHC polymorphisms in all CEHs, (2) unravels interrelationships between HLA and non-HLA haplotypical lineages, (3) resolves reported typing ambiguities and (4) describes haplospecific markers for a number of CEHs. Analysis also identified a DQA1 SNP and segments containing MHC class III polymorphisms that corresponded with class II (DRB3 and DRB4) lineages. These results portray the MHC where lineages containing non-HLA and HLA variants in linkage disequilibrium may operate in concert and can guide more thorough design and interpretation of HLA-disease relationships.