The MIC gene family

Antibody targeting tumor-derived soluble NKG2D ligand sMIC provides dual co-stimulation of CD8 T cells and enables sMIC+ tumors respond to PD1/PD-L1 blockade therapy

Background

Insufficient co-stimulation accounts for a great deal of the suboptimal activation of cytotoxic CD8 T cells (CTLs) and presumably unsatisfactory clinical expectation of PD1/PD-L1 therapy. Tumor-derived soluble NKG2D ligands are associated with poor clinical response to PD1/PD-L1 blockade therapy in cancer patients. One of the mostly occurring tumor-derived soluble NKG2D ligands, the soluble MHC I chain related molecule (sMIC) can impair co-stimulation to CD8 T cells. We investigated whether co-targeting sMIC can provide optimal co-stimulation to CTLs and enhance the therapeutic effect of PD1/PD-L1 blockades.

Methods

Single agent therapy of a PD1/PD-L1 blockade antibody or a sMIC-targeting non-blocking antibody or a combination therapy of the two antibodies were implied to well-characterized pre-clinical MIC/sMIC⁺ tumor models that closely resemble the NKG2D-mediated oncoimmune dynamics of MIC⁺ cancer patients. Therapeutic efficacy and associated effector mechanisms were evaluated.

Results

We show that antibody co-targeting sMIC enables or enhances the response of sMIC⁺ tumors to PD1/PD-L1 blockade therapy. The therapy response of the combination therapy was associated with enhanced antigen-specific CD8 T cell enrichment and function in tumors. We show that co-targeting sMIC with a nonblocking antibody provides antigen-specific CD8 T cells with NKG2D and CD28 dual co-stimulation, in addition to elimination of inhibitory signals, and thus amplifies antigen-specific CD8 T cell anti-tumor responses.

Conclusion

Our findings provide the proof-of-concept rationale and previously undiscovered mechanisms for co-targeting sMIC to enable and enhance the response to PD1/PD-L1 blockade therapy in sMIC⁺ cancer patients.

Electronic supplementary material

The online version of this article (10.1186/s40425-019-0693-y) contains supplementary material, which is available to authorized users.

Diversity and characterisation of polymorphic 3' untranslated region haplotypes of MICA and MICB genes

MICA and MICB genes encode ligands that interact with the natural killer (NK) cell activating receptor, NKG2D. These ligands display a highly polymorphic allelic repertoire, although the true functional significance of this polymorphism remains elusive. We previously reported additional polymorphism in the 5' untranslated region (UTR) proximal promoter region of these genes by sequencing international histocompatibility workshop (IHW) cell line DNA promoter and coding regions. The present study extends this analysis by further characterising the 3'UTR region of the same IHW reference panel to achieve a more complete understanding of MICA and MICB haplotype diversity and possible functional relevance. We found 17 extended MICA haplotypes encompassing the coding region and 3'UTR, including four novel haplotypes identified in IHW cell line DNA. This increased to 21 when also considering the 5'UTR proximal promoter region. Analysis of the MICB 3'UTR revealed two novel sequences in cell lines KLO and WIN designated MICB-UTR8 and UTR9, respectively. A total of 11 MICB haplotypes were identified in this study and five were unique. The present study, characterising MICA/B 3'UTR polymorphism utilising IHW reference cell lines, could be useful for future studies investigating the role of microRNA in post-transcriptional repression of gene expression and for immunotherapy strategies to combat cancer progression.

Single nucleotide polymorphisms within HLA region are associated with disease relapse for patients with unrelated cord blood transplantation

Disease relapse occurs in unrelated cord blood transplantation (CBT) even when the alleles of human leukocyte antigen (HLA) are fully matched between donor and recipient. This is similar to that observed in other types of hematopoietic stem cell transplantation. Fourteen single nucleotide polymorphisms (SNPs) within the HLA region have been reported previously by Petersdorf et al. and Piras et al. as transplantation determinants in unrelated hematopoietic cell transplantation. In this study, the genomic sequences within 500 base pairs upstream and downstream of the fourteen transplantation-related SNPs from 53 patients and their HLA-matched unrelated donors were analyzed for determining whether or not genetic variants, conferred by either recipient or donor SNP genotype or by recipient-donor SNP mismatching, were associated with the risk of relapse. Seven SNPs were associated with the risk of relapse in unrelated CBT. These included the donor genotype with the SNPs of rs2523675 and rs2518028 at the telomeric end of HCP5 gene, rs2071479 in the intron of the HLA-DOB gene, and rs2523958 in the MICD gene; and the recipient genotype with SNPs of rs9276982 in the HLA-DOA gene, and rs435766 and rs380924 in the MICD gene. As measured by pair-wise linkage disequilibrium (LD) with D′ as the parameter for normalized standard measurement of LD which compares the observed and expected frequencies of one haplotype comprised by alleles at different loci, rs2523675 had high LD with rs4713466 (D′ = 0.86) and rs2523676 (D′ = 0.91) in the HCP5 gene. The rs2518028 had no LD with all other SNPs except rs2523675 (D′ = 0.76). This study provides the basis for developing a method or algorithm for selecting better unrelated CBT candidate donors.

Fusion Proteins of NKG2D/NKG2DL in Cancer Immunotherapy

NKG2D (natural killer group 2, member D) is an important activating receptor in natural killer (NK) cells and some T cells. NKG2D ligands (NKG2DLs) are specifically expressed on most tumor cells. The engagement of these ligands on tumor cells to NKG2D on NK cells will induce cell-mediated cytotoxicity and have target cells destroyed. This gives NKG2D/NKG2DLs great potential in cancer therapeutic application. The creation of NKG2D/NKG2DL-based multi-functional fusion proteins is becoming one of the most promising strategies in immunotherapy for cancer. Antibodies, cytokines, and death receptors have been fused with NKG2D or its ligands to produce many powerful fusion proteins, including NKG2D-based chimeric antigen receptors (CARs). In this article, we review the recent developments of the fusion proteins with NKG2D/NKG2DL ligands in cancer immunotherapy.

Prognostic value of soluble major histocompatibility complex class I polypeptide-related sequence A in non-small-cell lung cancer - significance and development

Soluble major histocompatibility complex class I polypeptide-related sequence A (sMICA) is a useful marker in surveillance of lung cancer. High serum sMICA level in patients with non-small-cell lung cancer (NSCLC) seems to be a poor prognostic factor being correlated with poor differentiation and advanced stage. However, the low specificity limits its role as a single prognostic marker of NSCLC, but its evaluation, in addition to standard serum markers, could improve the staging of NSCLC. Despite promising, all current studies are insufficient to assess the real efficiency of sMICA as a prognostic marker of NSCLC, and hence, future studies are required to validate it.

MICA diversity and linkage disequilibrium with HLA-B alleles in renal-transplant candidates in southern Brazil

The major histocompatibility complex (MHC) class I chain-related gene A (MICA) is located centromerically to the human leukocyte antigen (HLA)-B. The short distance between these loci in the MHC indicates the presence of linkage disequilibrium (LD). Similarly to the HLA, the MICA is highly polymorphic, and this polymorphism has not been well documented in different populations. In this study, we estimated the allelic frequencies of MICA and the linkage disequilibrium with HLA-B alleles in 346 renal-transplant candidates in southern Brazil. MICA and HLA were typed using the polymerase chain reaction-sequence-specific primer method (PCR-SSO), combined with the Luminex technology. A total of 19 MICA allele groups were identified. The most frequent allele groups were MICA*008 (21.6%), MICA*002 (17.0%) and MICA*004 (14.8%). The most common haplotypes were MICA*009-B*51 (7.8%), MICA*004-B*44 (6.06%) and MICA*002-B*35 (5.63%). As expected from the proximity of the MICA and HLA-B loci, most haplotypes showed strong LD. Renal patients and healthy subjects in the same region of Brazil showed statistically significant differences in their MICA polymorphisms. The MICA*027 allele group was more frequent in renal patients (Pc = 0.018, OR: 3.421, 95% CI: 1.516–7.722), while the MICA*019 allele group was more frequent in healthy subjects (Pc = 0.001, OR: 0.027, 95% CI: 0.002–0.469). This study provided information on the distribution of MICA polymorphisms and linkage disequilibrium with HLA-B alleles in Brazilian renal-transplant candidates. This information should help to determine the mechanisms of susceptibility to different diseases in patients with chronic kidney disease, and to elucidate the mechanisms involved in allograft rejection associated with MICA polymorphisms in a Brazilian population.

Behçet’s Disease: A Review

Behçet’s disease (BD) is a multi-system inflammatory disorder dominated clinically by recurrent oral and genital ulceration, uveitis, and erythema nodosum. Behçet’s disease runs a chronic course, with unpredictable exacerbations and remissions whose frequency and severity may diminish with time. Behçet’s disease typically arises in young adults, although childhood-onset BD has also been reported. The disease can affect both genders and has a worldwide distribution, although it is more prevalent in countries of the ancient Silk Route. The cause of BD remains unknown, although an autoimmune reaction triggered by an infectious agent in a genetically predisposed individual has been suggested. The treatment of BD is symptomatic and empirical, but generally specific to the clinical features of each patient. The majority of affected individuals do not have life-threatening disease, although mortality can be associated with vascular-thrombotic and neurological disease.

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.

Diversity and characterization of polymorphic 5' promoter haplotypes of MICA and MICB genes

The major histocompatibility complex (MHC) class I-related chain A (MICA) and B (MICB) are ligands for the natural killer group 2, member D (NKG2D) activating receptor expressed on natural killer (NK) cells, natural killer T (NKT) cells, CD8+ T cells and γδ T cells. Natural killer group 2, member D (NKG2D) ligand expression is stress-related and upregulated by infected or oncogenic cells leading to cytolysis. MICA and MICB genes display considerable polymorphism among individuals and studies have investigated allelic association with disease and relevance of MICA in transplantation, with variable success. It is now known that promoters of MICA and MICB are polymorphic with some polymorphisms associating with reduced expression. We sequenced International Histocompatibility Workshop (IHW) cell line DNA to determine promoter types and alleles encoded by exons 2-6. We found 8 of 12 known MICA promoter polymorphisms and although promoter P7 dominated, other promoters associated with the same allele. For example, MICA*002:01 had promoters P3, P4 or P7 and the common MICA*008:01/04 type had P1, P6 or P7. Similarly, we sequenced 8 of 12 known MICB promoter haplotypes. Some coding region defined MICB alleles had a single promoter, for example, MICB*002:01 and promoter P9, whereas the promiscuous MICB*005 allele had promoters P1, P2, P5, P6, P10 or P12. The results indicate potential for variation in expression of MICA and MICB ligands between individuals with the same allelic types. If differential expression by polymorphic MICA and MICB promoters is confirmed by functional studies, involvement of these genes in disease susceptibility or adverse transplantation outcomes may require knowledge of both promoter and allelic types to make meaningful conclusions.

Identification of three MICA alleles in the genotype of a patient with chronic lymphocytic leukemia

Major histocompatibility complex (MHC) class I-related chain A gene (MICA) sequence-based genotyping (SBT) was attempted on a peripheral blood sample collected from a patient evaluated for hematopoietic stem cell retransplant. The electropherogram pattern of MICA SBT indicated the possibility of carrying more than two MICA alleles. Subsequent cloning and sequencing of the polymerase chain reaction products revealed the presence of three distinct MICA alleles: MICA*008:01/:04 (A5.1), MICA*007:01(A4), and MICA*002:01 (A9) in the genotype of this patient. The origin of the third extra MICA allele could not be determined and would require MICA genotyping information from other family members, which is unavailable.

Structural diversity of class I MHC-like molecules and its implications in binding specificities

The binding groove of class I major histocompatibility complex (MHC) class is essentially important for antigen binding and presentation on T cells. There are several molecules that have analogous conformations to class I MHC. However, they bind specifically to varying types of ligands and cell-surface receptors in order to elicit an immune response. To elucidate how such recognition is achieved in classical MHC-I like molecules, we have extensively analyzed the structure of human leukocyte antigen (HLA-1), neonatal Fc receptor (FcRn), hereditary hemochromatosis protein (HFE), cluster of differentiation 1 (CD1), gamma delta T cell receptor ligand (Τ22), zinc-α2-glycoprotein (ZAG), and MHC class I chain-related (MIC-A) proteins. All these molecules have analogous structural anatomy, divided into three distinct domains, where α1-α2 superdomains form a groove-like structure that potentially bind to certain ligand, while the α3 domain adopts a fold resembling immunoglobulin constant domains, and holds this α1-α2 platform and the light chain. We have observed many remarkable features of α1-α2 platform, which provide specificities to these proteins toward a particular class of ligands. The relative orientation of α1, α2, and α3 domains is primarily responsible for the specificity to the light chain. Interestingly, light chain of all these proteins is β₂-microglobulin (β₂M), except ZAG which has prolactin-induced protein (PIP). However, MIC-A is devoid of any light chain. Residues on β₂M recognize a sequence motif on the α3 domain that is essentially restricted to specific heavy chain of MHC class I molecules. Our analysis suggests that the structural features of class I molecules determine the recognition of different ligands and light chains, which are responsible for their corresponding functions through an inherent mechanism.

MICB0106 gene polymorphism is associated with ulcerative colitis in central China

BACKGROUND

The highly polymorphic nonclassical MHC class I chain-related genes A and B (MICA and MICB) encode stress-inducible glycoproteins expressed on various epithelial cells including intestinal epithelial cells. MICA and MICB gene polymorphisms and expressions are associated with autoimmune diseases but not known in ulcerative colitis (UC).

AIMS

To investigate the association of MICB exon 2-4 polymorphisms and soluble MICA (sMICA) expression with the susceptibility of UC in central China.

MATERIALS AND METHODS

Genomic DNA was isolated from peripheral blood. The allele frequencies of MICB exon 2-4 were genotyped in 105 UC patients and 213 healthy controls by PCR single-stranded conformation polymorphism method. Thirty-two patients and 32 controls were selected for determining serum sMICA expression by ELISA.

RESULTS

Allele frequency of MICB0106 was significantly higher in UC patients than in healthy controls (19.0% vs. 8.9%, corrected P (Pc) = 0.0006), especially in patients with extensive colitis (24.4% vs. 8.9%, Pc = 0.0006), moderate and severe disease (24.1% vs. 8.9%, Pc = 0.0006), extraintestinal manifestations (20.5% vs. 8.9%, Pc = 0.012), male patients (22.1% vs. 8.0%, Pc = 0.006), and patients over the age of 40 years (28.8% vs. 8.3%, Pc = 0.0006). The sMICA level was significantly higher in UC than in healthy controls (604.41 +/- 480.43 pg/ml vs. 175.37 +/- 28.31 pg/ml, P = 0.0001) but not associated with the MICB0106 genotypes.

CONCLUSIONS

Overall, MICB0106 allele was positively associated with UC in the Han Chinese in central China. sMICA was highly expressed in UC but not associated with the MICB0106 genotype.

Porcine cells express more than one functional ligand for the human lymphocyte activating receptor NKG2D

BACKGROUND

Xenotransplantation could ameliorate the severe shortage of donor organs. The initial results of transplantation from genetically-modified pig donors to primate recipients suggest that hyperacute rejection can be overcome, but thrombotic microangiopathy and the human anti-pig cellular immune response remain as significant impediments to successful clinical xenotransplantation. NKG2D is an activating immunoreceptor found on human natural killer (HuNK) cells, CD8(+) and gammadelta T cells. Signaling through NKG2D mediates cytotoxicity and cytokine secretion by NK cells and co-stimulation of T cells.

METHODS

Chinese hamster ovary P (CHOP) cells were transfected with human NKG2D and used in cell-cell binding studies with porcine epithelial, and endothelial cell lines. Soluble recombinant NKG2D-Fc was used to stain various porcine cells and tissues to indicate ligand expression. Porcine cells were used as targets in cytotoxicity assays with the HuNK cell lines NKL and YT, with and without enzymatic removal of pULBP1 and antibody blockade of NKG2D signaling.

RESULTS AND CONCLUSIONS

In this study, we demonstrate the expression of ligands for human NKG2D on porcine cell lines of endothelial and epithelial origin, islet cell clusters and rejecting kidney. HuNK cells were activated to kill pig cells expressing NKG2D ligands, and cytotoxicity was inhibited by antibody blockade of NKG2D. A previous study identified pULBP1 as the principal ligand for human NKG2D on pig aortic endothelial cells. In the current study, renal epithelial and intestinal endothelial cells each expressed high surface levels of pULBP1, but binding of soluble recombinant NKG2D and NKG2D-dependent cytotoxicity against these cells persisted after the enzymatic removal of pULBP1, strongly suggesting the presence of at least one additional functional ligand for human NKG2D in these cell types.

Role of major histocompatibility complex class I-related molecules A*A5.1 allele in ulcerative colitis in Chinese patients

The major histocompatibility complex (MHC) class I-related molecules A (MICA) is a stress-inducible cell surface antigen that is recognized by intestinal epithelial Vdelta1 gammadelta T cells, natural killer (NK) cells and CD8(+) T cells with NKG2D receptor participating in the immunological reaction in the intestinal mucosa. The present study aimed to investigate the functions of the MICA*A5.1 allele in the development of ulcerative colitis (UC) in the Chinese population. The microsatellite polymorphisms of MICA were genotyped in 124 unrelated Chinese patients with UC and 172 ethnically matched healthy controls using a semiautomatic fluorescently labelled polymerase chain reaction. MICA*A5.1-expressing Raji cells were generated by gene transfection. Cytotoxicity of NK cells to Raji cells expressing different MICA molecules was detected using the lactate dehydrogenase method. Soluble MICA in the culture supernatant was detected by enzyme-linked immunosorbent assay. The frequency of MICA*A5.1 was significantly higher in UC patients compared with the healthy controls (29.0% versus 17.4%, P = 0.001, corrected P = 0.005, OR = 1.936, 95% CI 1.310-2.863) and the frequency of a MICA*A5.1/A5.1 homozygous genotype was increased in UC patients (18.5% versus 7% in healthy controls, P = 0.0032, corrected P = 0.048, OR = 3.036, 95% CI 1.447-6.372). Raji cells with MICA*A5.1 expression produced more soluble MICA (t = 5.75, P < 0.01) than Raji cells with full-length MICA expression in culture supernatant. Raji cells with MICA*A5.1 expression were more resistant to killing by NK cells than Raji cells with full-length MICA expression. The MICA*A5.1 allele and MICA*A5.1/A5.1 genotype are significantly associated with Chinese UC patients in central China. MICA*A5.1 may play a role in the development of UC by producing more soluble MICA and resistance to NK cells.

Structurally based epitope analysis of major histocompatibility complex class I-related chain A (MICA) antibody specificity patterns

Recent studies have suggested a clinical significance to the detection of anti-major histocompatibility complex class I-related chain A (MICA) antibodies in transplantation. We have developed an eplet-based version of the HLAMatchmaker algorithm to assess the epitope specificity of these antibodies. Molecular viewing of the MICA structure and the determination of amino acid sequence differences between MICA alleles has yielded a repertoire of 38 potentially immunogenic MICA eplets. These eplets are based on the functional epitope structure that considers a configuration of amino acids within a 3-Angstrom radius of an antibody-accessible polymorphic residue on the molecular surface. In this study MICA-reactive sera were screened in Luminex assays with single MICA allele panels and analyzed with HLAMatchmaker. We identified reactivity patterns that correspond to eplet-specific antibodies to identify of unacceptable MICA mismatches including those alleles that have not been tested with the serum. In conclusion, HLAMatchmaker is a useful algorithm to analyze the reactivity patterns of anti-MICA antibodies and the determination of MICA mismatch acceptability at the structural level.

Anti-major histocompatibility complex class I-related chain A antibodies in organ transplantation

Candidate trigger antigens for alloreactive responses have been appearing continuously in the organ transplant scenario. Major histocompatibility complex class I-related chain A (MICA) is a polymorphic gene family, located near the HLA-B locus on chromosome 6, that encode a 62-kd cell surface glycoprotein. Endothelial cells, in addition to many cell lines, express MICA, whereas resting lymphocytes do not, making this polymorphic molecule a target for both cellular and humoral immune responses. Major histocompatibility complex class I-related chain A antigens are able to elicit the synthesis of alloantibodies in transplant recipients. These antibodies have been found in association with irreversible allograft rejection, an increased frequency of acute rejection episodes, and a significantly lower deceased donor graft survival, as well as in the eluates from rejected grafts. This review summarizes currently available information on MICA in the transplant setting. Undoubtedly, the questions that have surfaced surpass in excess the currently available answers.

MICA gene polymorphism in the pathogenesis of type 1 diabetes

Type 1 diabetes mellitus (T1DM) is a typical autoimmune disease and results from the destruction of insulin-producing beta cells of the pancreas. It develops in the presence of genetic susceptibility, even though more than 85% of patients with T1DM do not have a close relative with the disorder. The etiology of T1DM is complex, and both genetic and environmental factors play important roles. A permissive genetic background is required for the development of the islet autoimmune process. The strongest genetic association idengified is that with HLA class II genes located on the short arm of chromosome 6. It is well known that both HLA DRB1*04-DQA1*0301-DQB1*0302 (DR4-DQ8) and DRB1*03-DQA1*0501-DQB1*0201 (DR3-DQ2) are positively, and DRB1*15-DQA1*0102-DQB1*0602 is negatively, associated with T1DM. However, only a minority of the subjects carrying the high-risk haplotypes/genotypes develops the disease, which suggests that additional genes play a crucial role in conferring either protection or susceptibility to T1DM. Major histocompatibility complex (MHC) class I chain-related A (MICA) is located in a candidate susceptibility region and activates natural killer (NK) cells, T cells and gammadelta CD8 T cells by its receptor NKG2D. The polymorphism of the MICA gene is associated with T1DM in different populations as demonstrated in several papers published in the last 7 years.

Association of polymorphic extracellular domains of MICA with cervical cancer in northeastern Thai population

Cancer of the cervix is one of the common cancers among women worldwide. The primary risk factor of cervical cancer is the high-risk group human papillomavirus infection. Host genetic factors should also be involved. Major histocompatibility complex class I chain related A (MICA), a ligand to the natural killer cell receptor group (NKG)2D receptor relevant to immune surveillance, was investigated as a potential candidate. MICA is highly polymorphic. Although the data were limited regarding functional polymorphism, it is conceivable that polymorphism of MICA may contribute to different degree of immune activation caused by different NKG2D-binding affinity, acting as a susceptible factor for development of cervical cancer. In this study, we have developed a polymerase chain reaction-sequence-specific primer technique defining most of MICA alleles with a total of 41 primer mixes. This set of primers could especially discriminate MICA*045 (formerly 052), a common allele in northeastern Thai population, from MICA*00701, a common allele in Caucasian population. Based on the distribution of MICA in northeastern Thai population, only 27 primer mixes were required to screen the MICA polymorphisms in this population. This set of primers was used for MICA typing of 100 samples of cervical cancer compared with 94 samples of healthy northeastern Thai females (NETF). Thirteen alleles or groups of alleles were identified in these samples. Common alleles in our population were MICA*00801(027,048)/0803, MICA*010 and MICA*00201(020, 023, 050)/30/41. Statistically significant differences were not observed in the distributions of MICA alleles between different stages of patients and the control group. However, there were particular residues that were negatively associated with cervical cancer, suggesting active MICA motifs in immune activation.

MICA and MICB overexpression in oral squamous cell carcinoma

BACKGROUND

The concentration of MICA in serum seems be a good candidate marker in cancer. Previous studies from our laboratory have shown that the polymorphic MIC gene may confer a risk for oral squamous cell carcinoma (OSCC). The study investigated the expression levels of MICA and MICB of OSCC patients and cancer cell lines.

MATERIAL AND METHODS

We used RT-PCR to analyze the mRNA expression of MICA and MICB in four oral cancer cell lines compared with three normal human oral keratinocyte (NHOK) cell lines and in tissues from 36 patients with OSCC comparing tumor tissue with non-cancerous matched tissue (NCMT).

RESULTS

Endogenous MICB mRNA expression in OSCC cell lines was significantly higher than that in NHOK (1.40 +/- 0.27 vs. 0.40 +/- 0.16; P = 0.04). In 20 of 36 sets of tissue from patients with OSCC, MICB mRNA expression was higher in the cancerous tissue than in the NCMT. The mean MICB mRNA expression in OSCC tissues was significantly higher than in NCMT (0.39 +/- 0.08 vs. 0.14 +/- 0.03, P = 0.009, paired t-test). A significantly lower MICA mRNA was found in patients who chewed areca nut compared with those who did not use areca (P = 0.001) and in patients with well-differentiated tumors compared with those with less well-differentiated tumors (P = 0.02).

CONCLUSION

MICA and MICB mRNA expression may be increased in OSCC but there appears to be individual variation.

Heat Shock Up-Regulates lmp2 and lmp7 and Enhances Presentation of Immunoproteasome-Dependent Epitopes

The heat shock response is a canonical regulatory pathway by which cellular stressors such as heat and oxidative stress alter the expression of stress-responsive genes. Some of these stress-responsive genes (heat shock proteins and MHC class I (MHC I)-related chains) play a significant role in the immune system. In this study, we have investigated the impact of stimulating the heat shock response on genes involved in the MHC I presentation pathway. We report that two inducible subunits of the proteasome, lmp2 and lmp7, are transcriptionally up-regulated by heat shock in cells of mouse and human origin. Furthermore, heat-shocked cells show enhanced presentation of the immunoproteasome-dependent MHC I antigenic epitopes NP(118-126) of lymphocytic choriomeningitis virus and E1B(192-200) of adenovirus, but not immunoproteasome-independent epitopes such as tumor Ag AH1 and SV40 large T Ag epitope II(223-231). These findings show a novel immunological sequel to the cellular response to stress that may play a key role during fever or other homeostatic perturbations.

AluyMICB dimorphism within the class I region of the major histocompatibility complex is associated with asthma and airflow obstruction in the Busselton population

AIM

To examine the association between the Alu dimorphism within the first intron of the MICB gene and asthma and airflow obstruction. Background The highly polymorphic non-classical MHC class I polypeptide-related (MIC) genes, MICA and MICB, encode stress inducible glycoproteins, which are expressed on a variety of epithelial cells, including those of the lungs.

METHODS

AluyMICB genotyping was performed on 1109 subjects from the Busselton Health Study. From a standard questionnaire, 359 individuals indicated that they had been diagnosed by a doctor with asthma. Lung function was assessed by the forced expired volume in 1 second (FEV1) and expressed as a percent of the predicted value. Airflow obstruction was defined as FEV1<80% predicted.

RESULTS

In men, a dominant relationship was found between the AluyMICB DD genotype and asthma (P=0.006; chi2(2)=7.65). Furthermore, multivariate analysis adjusted for age, height, weight and body mass index (BMI) showed a relationship between DD genotype and asthma in men in a dominant model (odds ratio (OR)=1.97; 95% confidence interval (CI)=1.11-3.51; P=0.021). In women, an association was found between the AluyMICB II genotype and FEV1 percent predicted as a continuous variable (P=0.001). When adjusted for age and BMI, it showed a significant relationship between AluyMICB and airflow obstruction in a dominant model (OR=14.11%, 95% CI 3.29-60.57, P<0.001). However, no association was found between the AluyMICB II genotypes and airflow obstruction in men.

CONCLUSION

These findings suggest the possible involvement of a MHC class I gene in abnormal airway structure in women and airway function in men.

MICB microsatellite polymorphism is associated with ulcerative colitis in Chinese population

The MHC class I-related molecules A and B (MICA and MICB) are stress-inducible cell surface antigens that are recognized by immunocytes bearing the receptor NKG2D, including intestinal epithelial Vdelta1 gammadelta T cells, which may play a role in immunological reaction in intestinal mucosa. The present study was aimed to investigate the association of the microsatellite polymorphisms in the intron 1 of MICB and the MICA-MICB haplotype with the susceptibility to ulcerative colitis (UC) in Chinese population. The microsatellite polymorphisms of MICB were genotyped in unrelated 127 Chinese patients with UC and 193 ethnically matched healthy controls by a semiautomatic fluorescently labeled PCR method. All the subjects were the Chinese with Han nationality. The frequency of MICB-CA18 was significantly higher in UC patients compared with the healthy controls (14.0% vs. 5.8%, P = 0.0016, Pc = 0.024, OR = 2.637, 95%CI: 1.443-4.820) and was increased in the female patients compared with the female healthy controls (18.3% vs. 4.1%, P = 0.0006, Pc = 0.0080, OR = 5.224, 95%CI: 1.940-14.069). Thus, MICB-CA18 is positively associated with UC and female UC patients in Chinese population.

THE TORTUOUS JOURNEY OF A BIOCHEMIST TO IMMUNOLAND AND WHAT HE FOUND THERE

After starting out to become a physician, by a series of accidents I found myself at NIH in 1951 during its most productive growth phase. At age 26, I had a fully funded, independent laboratory and did not know what to work on. With advice from colleagues, I initiated a study of how penicillin kills bacteria. Twenty years later, my lab had outlined the structure and biosynthesis of the peptidoglycan of bacterial cell walls and had discovered that penicillin inhibited the terminal step in its biosynthesis catalyzed by transpeptidases. I then switched fields, moving to Harvard in 1968 and beginning the study of human HLA proteins. Twenty-five years later, the last half of which was spent in a stimulating collaboration with the late Don Wiley, our labs had isolated, crystallized, and elucidated the three-dimensional structures of these molecules and shown that their principal function was to present peptides to the immune system in initiating an immune response. More recently, the laboratory has focused on natural killer cells and their roles in peripheral blood and in the pregnant uterine decidua. It has been a wonderful scientific journey.

Prevalent expression of the immunostimulatory MHC class I chain-related molecule is counteracted by shedding in prostate cancer

The MHC class I chain-related molecules (MICs) have previously been shown to be induced on most epithelial tumor cells. Engagement of MIC by the activating immune receptor NKG2D triggers NK cells and augments antigen-specific CTL anti-tumor immunity. The MIC-NKG2D system was proposed to participate in epithelial tumor immune surveillance. Paradoxically, studies suggest that tumors may evade MIC-NKG2D-mediated immunity by MIC shedding-induced impairment of effector cell function. Here we demonstrate the first evidence to our knowledge of a significant correlation of MIC shedding and deficiency in NK cell function with the grade of disease in prostate cancer. MIC is widely expressed in prostate carcinoma. The presence of surface target MIC, however, is counteracted by shedding. A significant increase in serum levels of soluble MIC (sMIC) and deficiency in NK cell function was shown in patients with advanced cancer. Finally, the deficiency in NK cell function can be overcome by treatment with IL-2 or IL-15 in vitro. Our results suggest that (a) deficiency in MIC-NKG2D immune surveillance may contribute to prostate cancer progression, (b) sMIC may be a novel biomarker for prostate cancer, and (c) using cytokines to restore MIC-NKG2D-mediated immunity may have clinical significance for prostate cancer in cell-based adaptive immunotherapy.

The increase of MICA gene A9 allele associated with gastric cancer and less schirrous change

Since surgical resection is the principal treatment of gastric cancer, early detection is the only effective strategy against this disease at present. Recently, a new polymorphic gene family, the major histocompatibility complex class I chain-related (MIC) genes located about 40 kb centromeric to HLA-B gene has been proposed. This family consists of five genes (A, B, C, D and E). Among them, MICA has five various alleles (A4, A5, A5.1, A6 and A9), which can be used as a polymorphic marker for genetic mapping and for disease susceptibility. The MICA polymorphism was studied in our gastric cancer patients to see if there is any possible correlation with genetic predisposition and clinicopathological factors. Genomic DNA was extracted from fresh or frozen peripheral blood leukocytes in 107 patients with gastric adenocarcinoma who underwent gastrectomy in our hospital and 351 noncancer controls. MICA polymorphism was analysed by using PCR-based technique. The results showed both phenotypic and allele frequencies of allele A9 in patients with gastric cancer were significantly higher than controls (33 vs 17.6%, P=0.005; 17 vs 9.9%, P=0.02). Gastric adenocarcinoma with allele A9 was associated with less schirrous change than those without (P=0.014). MICA gene A9 allele might confer the risk of gastric cancer and associate with less schirrous change. The mechanisms among them deserve further investigation.

Association between the transmembrane region polymorphism of MHC class I chain related gene-A and type 1 diabetes mellitus in Sweden

Major histocompatibility complex (MHC) class I chain related gene-A (MIC-A) is associated with type 1 diabetes mellitus (T1DM) in other populations. We tested the association of MIC-A gene polymorphism with T1DM in Swedish Caucasians; if it has an age-dependent association; and if the association has an effect on gender. We studied 635 T1DM patients and 503 matched controls in the age group of 0-35 years old. MIC-A5 was significantly increased in T1DM compared with controls (odds ratio [OR] =1.81, p(c) < 0.0005). Logistic regression analysis revealed MIC-A5 association was independent of HLA. MIC-A5 with DR4-DQ8 or MIC-A5 with DR3-DQ2 gave higher OR than the OR obtained with either of them alone (OR = 1.81, 7.1, and 3.6, respectively). MIC-A5 was positively (OR = 2.48, p(c) < 0.0005) and MIC-A6 negatively associated (OR = 0.61, p(c) = 0.035) with the disease in < or = 20 years of age. The negative association of MIC-A6 in young onset was confirmed by logistic regression analysis. MIC-A5 was associated with the disease in males (OR = 2.05, p(c) = 0.0005). MIC-A6 conferred protection (OR = 0.098, p(c) = 0.032) in females heterozygous for DR3/DR4. In conclusion, MIC-A5 is associated with T1DM; the association was higher in individuals < or = 20 years old; and negative association of MIC-A6 was stronger in younger onset patients than in older onset patients.

Hyperkeratosis and leukocytosis in transgenic mice carrying MHC class I chain-related gene B (MICB)

Major histocompatibility complex (MHC) class I chain-related gene A and B (MICA and MICB) are located very close to HLA-B. MICA is reported to be strongly associated with Behçet's disease (BD), a multisysytemic inflammation disorder characterized by oral apthous ulcers, skin lesions and genital ulcers. These two molecules are highly conserved at the amino acid levels. To determine the function of MICB in vivo and the relationship between the expression of MICB and BD experimentally, we produced several transgenic mouse lines (termed CAG-MICB) expressing human MICB cDNA under a ubiquitous promoter. They exhibited a 50% increase in the number of white blood cells compared with their non-transgenic littermates, and also exhibited a 10-20% reduction in body weight compared with non-transgenic littermates. Exfoliation of the skin first appeared around 7 days after birth and disappeared after 2 weeks of age. This was repeatedly observed in the transgenic offspring of two independent CAG-MICB lines examined. Histopathological analysis of skin of young mice exhibiting skin abnormalities revealed hyperkeratosis of the epidermis and thickening of the granular layer with slight infiltration of inflammatory cells in the dermis without any vasculitis. Other remarkable abnormalities associated with BD have not been observed in the CAG-MICB lines. Furthermore, fluorescein angiography of eyes of the CAG-MICB lines was performed, but there were no marked changes of BD-related uveitis in the ocular fundus. These findings suggest that (i) MICB expression is related to temporary skin inflammation, and (ii) expression of MICB is not directly associated with BD.

Distribution of MICA alleles and haplotypes associated with HLA in the Korean population

The MICA (MHC class I chain-related gene A) is a polymorphic gene located 46 kb centromeric of the HLA-B gene, and is preferentially expressed in epithelial cells and intestinal mucosa. The MICA gene, similar to human leukocyte antigen (HLA) class I, displays a high degree of genetic polymorphism in exons 2, 3, 4, and 5, amounting to 54 alleles. In this study, we investigated the polymorphisms at exons coding for extracellular domains (exons 2, 3, and 4), and the GCT repeat polymorphism at the transmembrane (exon 5) of MICA in 199 unrelated healthy Koreans. Eight alleles were observed in the Korean population, with allele frequencies for MICA*010, MICA*00201, MICA*027, MICA*004, MICA*012, MICA*00801, MICA*00901, and MICA*00701 being 18.3%, 17.8%, 13.6%, 12.3%, 11.1%, 10.8%, 10.6%, and 3.3%, respectively. Strong linkage disequilibria were also observed between the MICA and HLA-B gene-MICA*00201-B58, MICA*004-B44, MICA*00701-B27, MICA*00801-B60, MICA*00901-B51, MICA*010-B62, MICA*012-B54, and MICA*027-B61. In the analysis of the haplotypes of HLA class I genes (HLA-A, B, and C) and the MICA, the most common haplotype was MICA*004-A33-B44-Cw*07, followed by MICA*00201-A2-B58-Cw*0302 and MICA*012-A2-B54-Cw*0102. The MICA null haplotype might be identified in the HLA-B48 homozygous individual. These results will provide an understanding of the role of MICA in transplantation, disease association, and population analyses in Koreans.

High resolution MIC genotyping: design and application to the investigation of inflammatory bowel disease susceptibility

The highly polymorphic nonclassical MHC class I chain-related (MIC) genes MICA and MICB encode stress inducible glycoproteins expressed on a variety of epithelial cells including intestinal cells. Interaction with the receptor NKG2D is likely to provide an important costimulatory signal for activation and proliferation of NK cells, activated macrophages and CD8 alphabeta and gammadelta T cells. Fifty-four MICA and 17 MICB alleles have been described to date. Although the functional significance of this polymorphism is not known, the high degree of nonconservative substitution, concentration to the putative ligand-binding site and recent observation that different MICA alleles bind to NKG2D with varying affinity has generated much interest. The MIC genes are attractive functional and positional candidate genes for inflammatory bowel disease susceptibility as a consequence of their position in the HLA region and expression on the gastrointestinal epithelium. We developed a robust, high-resolution PCR-SSP genotyping method that can be incorporated into the standard 'Phototyping' system and which effectively identifies 46 of 54 MICA alleles, and all 17 MICB alleles. We applied this system in combination with microsatellite genotyping of the exon 5 variable number of tandem repeats (VNTR) to the investigation of genetic susceptibility to the inflammatory bowel diseases, ulcerative colitis and Crohn's disease. We studied 248 patients with Crohn's disease, 329 with ulcerative colitis and 354 ethnically matched controls. Linkage disequilibrium patterns between HLA-B, MICA and MICB are presented. Analysis by individual allele or by multilocus haplotype failed to identify any significant disease associations.

The increase in the frequency of MICA gene A6 allele in oral squamous cell carcinoma

BACKGROUND

Oral squamous cell carcinoma (OSCC) was reported to be associated with immune function. The MICA (MHC class I chain-related gene A) is expressed by keratinocytes and other epithelial cells, and its encoded protein interacts with gamma/delta T cells localized in submucosa. The MICA also influences the heat shock protein function. We speculated that the alterations of MICA might influence the pathogenesis of OSCC through the aberration in presenting tumor antigens or heat shock protein. MICA gene has a triplet repeat (GCT) polymorphism in the transmembrane domain, resulting in five distinctive allelic patterns.

METHODS

We analysed this MICA polymorphism in 67 OSCC patients and 351 randomly selected unrelated controls. By using the ABI Prism 377-18 DNA sequencer (Applied Biosystems, Foster City, CA, USA) to analyse the sample DNA PCR products. The number of micro-satellite repeats was estimated with Genescan 672 software (Applied Biosystems) with a standard size marker of GS-350 TAMRA (N,N,N,N-tetramethyl-6-carbohydroxyl rhodamine; Applied Biosystems).

RESULTS

The phenotype frequency of allele A6 of MICA in subjects with OSCC was significantly higher than that in controls (RR = 3.46, 95% CI = 1.73-6.94, P = 0.0002), as was the frequency of allele (RR = 2.64, 95% CI = 1.39-5.02, P = 0.002).

CONCLUSION

The results suggest that allele A6 in MICA might confer the risk of OSCC.

Genetics of latent autoimmune diabetes in adults

Slowly progressive insulin-dependent diabetes mellitus (IDDM), like classical IDDM, is also associated with genetic markers. HLA-DR3 but not DR4 is associated with latent autoimmune diabetes in adults (LADA). In GAD65 antibody-positive Finnish LADA patients, DQB1*0302 is positively associated with the disease. Alleles of the MHC class I chain-related A (MICA) gene located centromeric to the HLA-B gene is associated with LADA. Allele 5.1 of MICA was associated with both LADA and adult-onset Italian IDDM patients when compared to controls. This finding was also observed in Indian and Latvian patients with LADA. These findings suggest that certain genetic markers distinguish LADA better.

MICA gene polymorphism is not associated with an increased risk for skin cancer

The MICA gene encodes for major histocompatibility complex class I chain-related proteins (MIC), which belong to a recently identified new family of nonclassical major histocompatibility complex molecules. The general structure of the MICA molecule resembles that of major histocompatibility complex class I molecules. MIC molecules are considered to be stress-induced antigens that are recognized by cytotoxic T cells and natural killer cells, which play an important role in the surveillance of transformed infected and damaged cells. Associations of major histocompatibility complex class I molecules with skin cancer have been described before. To evaluate the possible association of MICA gene polymorphism with the risk for nonmelanoma skin cancer we evaluated 153 cases with squamous cell carcinoma, 261 cases with basal cell carcinoma, 111 controls with malignant melanoma, and 247 controls without a history of skin cancer. Five distinct MICA alleles A4, A5, A6, A9, and A5.1 were studied. As the MICA 5.1 variant gene contains a four-nucleotide insertion that causes a stop codon in the trans membrane region, the resulting truncated MICA molecule does not reside on the cellular membrane. In the case of individuals who are homozygous for MICA 5.1 this results in cells that are naked for the MICA molecule. We therefore specifically addressed the possible association between MICA 5.1 homozygosity and skin cancer, as these individuals are expected to be at the highest risk for skin cancer if the MICA gene plays a role in skin carcinogenesis. Viral proteins may serve as antigens for recognition of skin cancer by the immune system. Human papillomavirus is the most likely candidate virus to be involved in the carcinogenesis of cutaneous squamous cell carcinoma. Hence, we also assessed the association between MICA polymorphism and squamous cell carcinoma in human-papillomavirus-positive and human-papillomavirus-negative individuals as identified by the presence of human papillomavirus DNA in hairs plucked from their eyebrows. Our analyses did not reveal any significant differences regarding the MICA allele frequencies between cases and controls. Also homozygotes and heterozygotes for the MICA 5.1 variant gene were not at an increased risk for skin cancer compared to individuals without this variant gene and infection with human papillomavirus did not materially influence these findings. The same group of cases and controls was large enough to show an association between melanocortin 1 receptor gene polymorphism and skin cancer and to reasonably exclude an association between p53 codon 72 polymorphism and skin cancer. Therefore, we conclude that an association between MICA gene polymorphism and nonmelanoma skin cancer is not likely.

Expression of stress-induced MHC class I related chain molecules on human melanoma

Cellular immune responses to melanoma are tightly regulated and include specific T cell responses to self antigens such as Mart-1 and gp100. Thus, additional signals apart from those mediated by the T cell receptor are needed to ensure T cell activation. Recently, the stress inducible major histocompatibility complex molecules, MHC class I related chain, were identified as an activator of both natural killer and T cells via interaction with their receptor NKG2D. Herein, we report the expression of MIC in 31 of 40 primary cutaneous melanomas and in 13 of 20 metastatic lesions. Moreover, lymphocytes infiltrating the tumor were found to express NKG2D. Detailed analysis identified both CD3+ T cells as well as CD56+ natural killer cells contributing to this NKG2D+ tumor infiltrating lymphocyte population present.

MICA is a target for complement-dependent cytotoxicity with mouse monoclonal antibodies and human alloantibodies

The highly polymorphic major histocompatibility class I related chain A (MICA) gene encodes glycoproteins that have been shown to be expressed in epithelial cells, endothelial cells, keratinocytes, monocytes, and tumor cells. In previous experiments, we have studied MICA antigens using rabbit sera obtained by immunization with MICA peptides. We also found that several transplant recipients had specific antibodies against MICA in an ELISA assay with recombinant of MICA (r-MICA). In the present work we produced monoclonal antibodies by immunization of mice with recombinant MICA*008. Based on the different patterns of reactivity observed in ELISA, Western blot, and flow cytometry, mAbs 1.9C2, 2.4F5, 1.7AD, and 2.3D4 only reacted with denatured MICA and mAb 1.7A8 and 3.2H3 reacted also with native MICA as illustrated by flow cytometry with live cells. These monoclonal antibodies were postulated to bind to different sites of the MICA molecule. In order to investigate whether MICA expressed on the cell surface is able to mediate cell killing, antibody absorption, flow cytometry and complement-dependent cytotoxicity (CDC) were performed. We found that mouse monoclonal antibody 3.2H3 was able to kill 70% of HeLa cells. Absorption of a patient serum with pooled human platelets to remove antibodies against class I HLA resulted in a small shift of fluorescence and reduced killing from 100% to 70-75%. Absorption with the platelets and r-MICA produced a remarkable reduction in fluorescence staining and virtually reduced complement-dependent killing to the level of the negative controls. The results suggested that MICA alloantigens may be more immunogenic than could have been previously suspected.

MICA and MICB microsatellite alleles in HLA extended haplotypes

The present study is a contribution to the definition of the linkage disequilibrium relationship of MICA and MICB with adjacent loci and to the characterization of extended HLA haplotypes. These issues are of importance for the identification of disease associations and for a better definition of donor-recipient compatibility in bone-marrow grafts through the typing of haplospecific markers. The distribution of the five alleles of MICA and the 13 alleles of MICB microsatellites, located, respectively, in MICA transmembrane exon 5 and in MICB intron 1, was examined in 133 healthy Italian individuals previously typed for HLA class I, class II and complement loci and for the TNFa microsatellite. The MICB microsatellite was also analysed in 49 HTCLs for which MICA typing was already available. Very strong linkage disequilibria with HLA-B and TNFa were detected in the Italian population for both MICA and MICB microsatellite alleles, in spite of the high mutability rate of the larger MICB alleles. Some strong associations were also detected between MICB and DRB1. The strongest associations (P < 0.001, D' > 0.7) were those of MICA-A4 with HLA-B18, B27 and TNFa1, MICA-A5 with HLA-B35, B61 and B62, MICA-A5.1 with HLA-B7, B8, B13, B63 and MICB-CA24, MICA-A6 with HLA-B51, MICA-A9 with HLA-B39, B57 and TNFa2, MICB-CA14 with HLA-B14, B27 and TNFa1, MICB-CA15 with HLA-B52, TNFa4 and TNFa13, MICB-CA17 with HLA-B7 and TNFa11, MICB-CA18 with HLA-B13 and TNFa7, MICB-CA22 with HLA-B57, and MICB-CA24 with HLA-B8 and TNFa2. From pairwise associations in the random panel and results for the homozygous cell lines it was possible to deduce the MICA and MICB microsatellite alleles present in many of the well-known Caucasoid extended haplotypes.

Typing for all known MICA alleles by group-specific PCR and SSOP

Major histocompatibility complex class I chain-related gene (MICA) is a recently discovered polymorphic gene in the HLA region expressed mainly by certain epithelial cells, keratinocytes, endothelial cells, fibroblasts, and monocytes. MICA is structurally quite different from the HLA class I genes and is potentially associated with some diseases and with immune response to transplants. Some DNA-based typing techniques have previously been described for MICA including sequence-based typing (SBT) and analysis of single strand conformational polymorphisms (SSCP). In the present experiments we have developed a strategy that allows identification of all 54 MICA alleles described so far, using group-specific polymerase chain reactions (PCR) and sequence-specific oligonucleotide probes (SSOP). To analyze for the polymorphisms in exons 2, 3, and 4 an initial screening with group-specific primers, based on polymorphism at position 69 of exon 2, and at position 615-616 of exon 4, was used to determine four major groups of alleles. Then group-specific PCR amplifications were performed and the amplified DNA was hybridized with the corresponding panels of SSOP. An additional amplification was performed with locus-specific primers and hybridized with a set of SSOP to identify and/or confirm the presence of some of the alleles. Unequivocal MICA typing was achieved for 97 of 103 individuals. Of 54 previously described alleles, only 14 were observed in this population. One unexpected hybridization pattern was observed, and molecular cloning and sequencing confirmed it to be a novel sequence, which was given the local designation MICA-055D. The gene frequencies among 103 unrelated North American Caucasian donors were determined and the linkage disequilibrium between MICA and HLA-B was analyzed.

MICA 5.1 allele is a susceptibility marker for psoriasis in the Korean population

In order to investigate the possibility that the MICA gene is involved in the pathogenesis of psoriasis, microsatellite polymorphism in the transmembrane region of MICA was studied in 138 Korean patients with psoriasis and compared with 126 healthy controls. The MICA 5.1 microsatellite allele, consisting of 5.1 repetitions of GCT/AGC, showed significantly higher frequencies in all patients and in patients with type I psoriasis than in the controls. HLA-A30-B13-Cw*0602-MICA 5.1 and A1-B37-Cw*0602-MICA 5.1 were found to be an extended haplotype associated with psoriasis. Our results suggest that the MICA 5.1 allele might be a genetic marker related to the early onset of psoriasis and play a secondary role to the HLA-Cw*0602 gene or an unknown causative gene closely linked to HLA-Cw*0602 in the genetic susceptibility to psoriasis.

On the MICA deleted-MICB null, HLA-B*4801 haplotype

A 100-kb deletion including the MICA gene was recently reported in the HLA-B48 (B*4801)-associated haplotype in Japanese. Interestingly, this MICA deletion is accompanied by a MICB null allele, MICB0107N. In order to further investigate the universality of the apparent tight linkage between these two events, we present data on high-resolution deletion mapping of eight HLA-B48-homozygous individuals. Among these, five carried the MICA deletion linked to MICB0107N, as originally reported. Conversely, the remaining three possessed an intact MICA gene of MICA008 or MICA010 allelic variant associated this time with a putative expressed MICB allele, MICB0102. These results may imply that the expression of both MICA and MICB molecules is indispensable to viability through a yet-to-be understood mutual interaction in immune surveillance.

Retinoic acid early inducible genes define a ligand family for the activating NKG2D receptor in mice

Here we describe a family of GPI-anchored cell surface proteins that function as ligands for the mouse activating NKG2D receptor. These molecules are encoded by the retinoic acid early inducible (RAE-1) and H60 minor histocompatibility antigen genes on mouse chromosome 10 and show weak homology with MHC class I. Expression of the NKG2D ligands is low or absent on normal, adult tissues; however, they are constitutively expressed on some tumors and upregulated by retinoic acid. Ectopic expression of RAE-1 and H60 confers target susceptibility to NK cell attack. These studies identify a family of ligands for the activating NKG2D receptor on NK and T cells, which may play an important role in innate and adaptive immunity.

A 356-Kb sequence of the subtelomeric part of the MHC Class I region

The subtelomeric part of the MHC Class I region contains 11 of the 21 genes described on chromosome 6 at position 6p21.3. The general organization of those and other genes resident in the region was revealed by determining a 356,376 bp sequence. Potential exons for new genes were identified by computer analysis and a large number of ESTs were selected by testing the sequence by the BLAST algorithm against the GenBank nonredundant and EST databases. Most of the ESTs are clustered in two regions. In contrast, the whole HLA-gene region is crammed with LINE and SINE repeats, fragments of genes and microsatellites, which tends to hinder the identification of new genes.

Human inhibitory and activating Ig-like receptors which modulate the function of myeloid cells

There is increasing evidence that myeloid cells express several receptor families, which include both inhibitory and stimulatory isoforms. The expression of receptor isoforms with similar specificities but opposite functions on the same cell is intriguing. What might be the interplay between these receptors? Some clues to the answer to this question may come from recent studies on two myeloid receptor families: the ILT/LIR/MIR (immunoglobulin-like transcript/leukocyte Ig-like receptor/monocyte/macrophage Ig-like receptor) and the SIRP (signal-regulatory protein).

MICA gene polymorphism and the risk to develop cervical intraepithelial neoplasia

Cervical intraepithelial neoplasia (CIN) is associated with human papillomaviruses (HPV) and the HLA genes. The MICA (MHC class I chain-related gene A) is expressed by keratinocytes and epithelial cells and interacts with gamma delta T cells. It is therefore possible that MICA might influence the pathogenesis of CIN and cervical cancer through presentation of viral or tumor antigens. To investigate this, we determined the MICA transmembrane allele frequencies in a prospective population-based cohort study from the Västerbotten County in northern Sweden. 74 women developed CIN. 153 control women who remained healthy during follow up were matched for age. Five polymorphic microsatellite alleles of MICA were identified by a polymerase chain reaction-based (PCR) technique using fluorescent-labeled primers. MICA A5 and A5.1 were the most common alleles in this population. None of the alleles of MICA were associated with disease. The frequency of MICA allele A5 was higher among HPV 18 seropositive than HPV 18 seronegative patients but this difference was not significant after the correction of p value. In conclusion, microsatellite allele polymorphism of MICA transmembrane part is not associated with cervical intraepithelial neoplasia.

Triplet repeat polymorphism in the MICA gene in HLA-B27 positive and negative caucasian patients with ankylosing spondylitis

Previously, we reported a triplet repeat polymorphism in the transmembrane region within the MICA gene closely linked to HLA-B in a limited number of B27-positive Caucasian patients with ankylosing spondylitis (AS) (N = 48). In this study, we enrolled much more patients including some negative for B27, 162 AS subjects consisting of 140 B27-positive, and 22 B27-negative patients. The microsatellite allele consisting of 4 repetitions of (GCT/AGC) (A4 allele) was present at a significantly higher phenotype frequency in the patient group than in the ethnically matched control group (Pc < 0.000001). However, the frequency of the A4 allele was not significantly higher in the B27-positive and B27-negative patient groups, as compared to the B27-positive and B27-negative control groups, respectively. The higher phenotype frequency of the A4 allele in the patient group was supposed to be due to a strong linkage disequilibrium between the MICA and HLA-B genes. Thus, the possibility that the MICA gene is involved in the pathogenesis of AS can be excluded, supporting the hypothesis of a primary association of AS with HLA-B27.

Genomics, Isoforms, Expression, and Phylogeny of the MHC Class I-Related MR1 Gene

A growing number of non-MHC-encoded class I-related molecules have been shown to perform diverse, yet essential, functions. These include T cell presentation of bacterially derived glycolipidic Ags by CD1, transcytosis of maternal IgG by the neonatal Fc receptor, enriched presence and plausible function within exocrine fluids of the Zn-α2-glycoprotein, subversion of NK cytolytic activity by the CMV UL18 gene product, and, finally, crucial involvement in iron homeostasis of the HFE gene. A recently described member of this family is the MHC class-I related (MR1) gene. The most notable feature of MR1 is undoubtedly its relatively high degree of sequence similarity to the MHC-encoded classical class I genes. The human chromosome 1q25.3 MR1 locus gives rise not only to the originally reported 1,263-bp cDNA clone encoding a putative 341-amino acid polypeptide chain, but to many additional transcripts in various tissues as well. Here we define the molecular identity of all human and murine MR1 isoforms generated through a complex scenario of alternative splicing, some encoding secretory variants lacking the Ig-like α3 domain. Moreover, we show ubiquitous transcription of these MR1 variants in several major cell lineages. We additionally report the complete 18,769-bp genomic structure of the MR1 locus, localize the murine orthologue to a syntenic segment of chromosome 1, and provide evidence for conservation of a single-copy MR1 gene throughout mammalian evolution. The 90% sequence identity between the human and mouse MR1 putative ligand binding domains together with the ubiquitous expression of this gene favor broad immunobiologic relevance.