MICA, MICB and C1_4_1 polymorphism in Crohn's disease and ulcerative colitis

Relationship between rs4349859 and rs116488202 polymorphisms close to MHC-I region and serum urate levels in patients with gout

BACKGROUND

Gout is the most common inflammatory rheumatic disease and elevated levels of serum urate (SU) are the main cause for its development. Major histocompatibility complex class 1 (MHC-1) plays an important role in the development of multiple inflammatory diseases; however, there is little evidence of its involvement in gout. The present study focused on evaluating the association of the rs4349859 and rs116488202 single nucleotide polymorphisms (SNPs) close to the MHC-1 region in patients with gout.

METHODS AND RESULTS

One hundred and seventy-six individuals of Mexican origin were included, of which 81 were patients with primary gout and 95 were healthy controls. The rs4349859 and rs116488202 SNPs were genotyped using TaqMan probes by allelic discrimination by real-time PCR. Serum concentrations of biochemical parameters were measured with enzymatic methods. Descriptive statistics were applied and P-values < 0.05 were considered significant. It was observed that the rs4349859 and rs116488202 SNPs showed significant association with the risk of gout (OR = 146, 95%CI = 44.8-480.2, P < 0.01; OR = 2885, 95%CI = 265-31398, P < 0.01, respectively). Our results also showed significantly higher serum SU levels in gout patients with respect to controls (P < 0.01) in the carriers of the GA genotype compared with the GG genotype of the rs4349859 variant, and in the carriers of the CT genotype compared with the CC genotype of the rs116488202 variant.

CONCLUSION

The study revealed that rs4349859 and rs116488202 SNPs close to MHC-I region confers strong susceptibility to gout in Mexican population, and the heterozygous genotypes of both were associated with higher levels of SU.

MICA ∗012:01 Allele Facilitates the Metastasis of KRAS-Mutant Colorectal Cancer

Major histocompatibility complex (HLA) class I chain-related protein A (MICA) regulates immune surveillance through activation of NKG2D (natural killer group 2D) receptor. However, the genetic association, potential function, and predictive ability of MICA alleles with colorectal cancer (CRC) prognosis remain undefined. In this study, we characterized MICA alleles in tissue samples from 104 patients with CRC and 536 healthy controls and carried out genetic association studies by molecular and clinical CRC phenotypes. Preliminary sequence analysis revealed that MICA ^∗009:01 or ^∗049 alleles were significantly decreased in patients with CRC (p = 0.0049), and further stratification analysis indicated that MICA ^∗012:01 allele was associated with patients with CRC and carrying KRAS codon 12 mutation (p = 0.027). The functional consequences of MICA alleles were examined via transfected CRC cell lines which showed that overexpression of MICA ^∗012:01 enhanced the proliferation, invasion, and metastatic phenotype of CRC. Preliminary analysis of disease-free survival time in patients with and without MICA ^∗012:01 suggest this allele may be predictive for poor prognosis of patients with KRAS codon 12 mutated CRC, as no somatic mutation of MICA gene was detected in CRC tumors compared to paracancerous tissues. Our study indicates that MICA ^∗012:01 allele is associated with KRAS-mutated CRC, facilitates CRC invasion and metastasis, and possibly reduces the survival of patients with KRAS-mutated CRC.

How Mucosal Epithelia Deal with Stress: Role of NKG2D/NKG2D Ligands during Inflammation

Mucosal epithelia encounter both physicochemical and biological stress during their life and have evolved several mechanisms to deal with them, including regulation of immune cell functions. Stressed and damaged cells need to be cleared to control local inflammation and trigger tissue healing. Engagement of the activating NKG2D receptor is one of the most direct mechanisms involved in the recognition of stressed cells by the immune system. Indeed, injured cells promptly express NKG2D ligands that in turn mediate the activation of lymphocytes of both innate and adaptive arms of the immune system. This review focuses on different conditions that are able to modulate NKG2D ligand expression on the epithelia. Special attention is given to the mechanisms of immunosurveillance mediated by natural killer cells, which are finely tuned by NKG2D. Different types of stress, including viral and bacterial infections, chronic inflammation, and cigarette smoke exposure, are discussed as paradigmatic conditions for NKG2D ligand modulation, and the implications for tissue homeostasis are discussed.

Anti-NKG2D mAb: A New Treatment for Crohn's Disease?

Crohn’s disease (CD) and ulcerative colitis (UC) are immunologically-mediated, debilitating conditions resulting from destructive inflammation of the gastrointestinal tract. The pathogenesis of IBD is incompletely understood, but is considered to be the result of an abnormal immune response with a wide range of cell types and proteins involved. Natural Killer Group 2D (NKG2D) is an activating receptor constitutively expressed on human Natural Killer (NK), γδ T, mucosal-associated invariant T (MAIT), CD56⁺ T, and CD8⁺ T cells. Activation of NKG2D triggers cellular proliferation, cytokine production, and target cell killing. Research into the NKG2D mechanism of action has primarily been focused on cancer and viral infections where cytotoxicity evasion is a concern. In human inflammatory bowel disease (IBD) this system is less characterized, but the ligands have been shown to be highly expressed during intestinal inflammation and the following receptor activation may contribute to tissue degeneration. A recent phase II clinical trial showed that an antibody against NKG2D induced clinical remission of CD in some patients, suggesting NKG2D and its ligands to be of importance in the pathogenesis of CD. This review will describe the receptor and its ligands in intestinal tissues and the clinical potential of blocking NKG2D in Crohn’s disease.

NKG2D ligand expression in Crohn's disease and NKG2D-dependent stimulation of CD8+ T cell migration

Interaction between the activating NKG2D receptor on lymphocytes and its ligands MICA, MICB, and ULBP1-6 modulate T and NK cell activity and may contribute to the pathogenesis of Crohn's disease (CD). NKG2D ligands are generally not expressed on the cell surface of normal, non-stressed cells, but expression of MICA and MICB in CD intestine has been reported. In this exploratory study, we further characterize the expression of NKG2D and its ligands, including the less well-described ULBP4-6, in CD, and test if NKG2D ligand interactions are involved in the migration of activated T cells into the affected mucosal compartments. Intestinal tissue from CD patients and healthy controls were analyzed by flow cytometry, mass cytometry, and immunohistochemistry for expression of NKG2D and ligands, and for cytokine release. Furthermore, NKG2D-dependent chemotaxis of activated CD8⁺ T cells across a monolayer of ligand-expressing human intestinal endothelial cells was examined. Activated lymphocytes down-regulated NKG2D expression upon accumulation in inflamed CD intestine. NKG2D expression on CD56⁺ T and γδ T cells from inflamed tissue seemed inversely correlated with CRP levels and cytokine release. B cells, monocytes, mucosal epithelium, and vascular endothelium expressed NKG2D ligands in inflamed CD intestine. The expression of NKG2D ligands was correlated with cytokine release, but was highly variable between patients. Stimulation of vascular intestinal endothelial cells in vitro induced expression of NKG2D ligands, including MICA/B and ULBP2/6. Blockade of NKG2D on CD8⁺ T cells inhibited the migration over ligand-expressing endothelial cells. Intestinal induction of NKG2D ligands and ligand-induced down-regulation of NKG2D in CD suggest that the NKG2D-ligand interaction may be involved in both the activation and recruitment of NKG2D⁺ lymphocytes into the inflamed CD intestine.

MICA*A4 protects against ulcerative colitis, whereas MICA*A5.1 is associated with abscess formation and age of onset

Ulcerative colitis (UC) is one of the two major forms of inflammatory bowel disease, the aetiology of which remains unknown. Several studies have demonstrated the genetic basis of disease, identifying more than 130 susceptibility loci. The major histocompatibility complex class I chain-related gene A (MICA) is a useful candidate to be involved in UC pathogenesis, because it could be important in recognizing the integrity of the epithelial cell and its response to stress. The aim of this study was to analyse the relationship between polymorphisms in the transmembrane domain of MICA and susceptibility to develop UC. A total of 340 patients with UC and 636 healthy controls were genotyped for MICA transmembrane polymorphism using a polymerase chain reaction (PCR) combined with fluorescent technology. Different MICA alleles were determined depending on the PCR product size. The allele MICA*A4 was less frequent in patients than in controls (P = 0·003; OR = 0·643), and this protective role is higher when it forms haplotype with B*27 (P = 0·002; OR = 0·294). The haplotype HLA-B*52/MICA*A6 was also associated with UC [P = 0·001; odds ratio (OR) = 2·914]. No other alleles, genotypes or haplotypes were related with UC risk. Moreover, MICA*A5.1 is associated independently with abscesses (P = 0·002; OR = 3·096) and its frequency is lower in patients diagnosed between ages 17 and 40 years (P = 0·007; OR = 0·633), meaning an extreme age on onset. No association with location, extra-intestinal manifestations or need for surgery was found.

Associations of MICA Polymorphisms with Inflammatory Rheumatic Diseases

Inflammatory rheumatic diseases are characterized by inflammation resulting from the immune dysregulation that usually attacks joints, skin and internal organs. Many of them are considered as complex disease that may be predisposed by multiple genes and/or genetic loci, and triggered by environmental factors such as microbiome and cellular stress. The major histocompatibility complex class I chain-related gene A (MICA) is a highly polymorphic gene that encodes protein variants expressed under cellular stress conditions, and these MICA variants play important roles in immune activation and surveillance. Recently, accumulating evidences from both genetic and functional studies have suggested that MICA polymorphisms may be associated with various rheumatic diseases, and the expression of MICA variants may attribute to the altered immune responses in the diseases. The objective of this review is to discuss potential genetic associations and pathological relevance of MICA in inflammatory rheumatic diseases that may help us to understand pathogenesis contributing to the development of these diseases.

Pathogenesis of human diffusely adhering Escherichia coli expressing Afa/Dr adhesins (Afa/Dr DAEC): current insights and future challenges

The pathogenicity and clinical pertinence of diffusely adhering Escherichia coli expressing the Afa/Dr adhesins (Afa/Dr DAEC) in urinary tract infections (UTIs) and pregnancy complications are well established. In contrast, the implication of intestinal Afa/Dr DAEC in diarrhea is still under debate. These strains are age dependently involved in diarrhea in children, are apparently not involved in diarrhea in adults, and can also be asymptomatic intestinal microbiota strains in children and adult. This comprehensive review analyzes the epidemiology and diagnosis and highlights recent progress which has improved the understanding of Afa/Dr DAEC pathogenesis. Here, I summarize the roles of Afa/Dr DAEC virulence factors, including Afa/Dr adhesins, flagella, Sat toxin, and pks island products, in the development of specific mechanisms of pathogenicity. In intestinal epithelial polarized cells, the Afa/Dr adhesins trigger cell membrane receptor clustering and activation of the linked cell signaling pathways, promote structural and functional cell lesions and injuries in intestinal barrier, induce proinflammatory responses, create angiogenesis, instigate epithelial-mesenchymal transition-like events, and lead to pks-dependent DNA damage. UTI-associated Afa/Dr DAEC strains, following adhesin-membrane receptor cell interactions and activation of associated lipid raft-dependent cell signaling pathways, internalize in a microtubule-dependent manner within urinary tract epithelial cells, develop a particular intracellular lifestyle, and trigger a toxin-dependent cell detachment. In response to Afa/Dr DAEC infection, the host epithelial cells generate antibacterial defense responses. Finally, I discuss a hypothetical role of intestinal Afa/Dr DAEC strains that can act as "silent pathogens" with the capacity to emerge as "pathobionts" for the development of inflammatory bowel disease and intestinal carcinogenesis.

Immunogenetic biomarkers in inflammatory bowel diseases: Role of the IBD3 region

Many studies have demonstrated the linkage between the IBD3 region (6p21.1-23), an area which encompasses the famous human leukocyte antigen (HLA) complex, and Crohn’s disease (CD) or ulcerative colitis (UC). IBD3 is the only region that meets genome-wide significance, and provides stronger evidence of the linkage than 16p13.1-16q12.2 (IBD1), the locus that contains the susceptibility gene CARD15. However, despite these findings, IBD3 susceptibility genes remain elusive and unclear due to the strong linkage disequilibrium, extensive polymorphism, and high gene density that characterize this area and also due to varying allele frequencies in populations around the world. This area presents an extremely high abundance of genes, including the classical and non-classical major histocompatibility complex (MHC) class I and II genes, and other genes, namely MHC class III genes tumor necrosis factor (TNF)-α and -β, and Hsp, whose proteins play key functions in immunological processes. To date, it is not clear which genes within the MHC family contribute to the IBD pathogenesis, although certain HLA alleles have been associated with IBD. Recent insights into the biological function of other genes encoded within the IBD3 region, such as the MHC class I chain-related (MIC) genes, have led investigators to a more comprehensive exploration of this region. MHC class I chain-related molecule A (MICA) is highly polymorphic and interacts with NKG2D, its receptor on the surface of NK, Tγδ and T CD8⁺ cells. Increased expression of MICA in intestinal epithelial cells and increased expression of NKG2D in CD4⁺ T cells (lamina propria) in patients with CD have also been reported. MICA alleles have also been associated with IBD, and a variation at amino acid position 129 of the α2-heavy chain domain seems to categorize MICA alleles into strong and weak binders of NKG2D receptor, thereby influencing the effector cells’ function. In this regard, a relevant role of MICA-129-Val/Met single nucleotide polymorphism has recently been implicated in the pathogenesis of IBD. TNF-α and -β also play an important role in inflammatory response. In fact, IBD is commonly treated with TNF-α inhibitors. Additionally, polymorphisms of TNF-α gene are known to affect the gene expression level and particular TNF-α genotypes may influence the response of IBD patients treated with TNF-α inhibitors.

Pathogenesis of human enterovirulent bacteria: lessons from cultured, fully differentiated human colon cancer cell lines

Hosts are protected from attack by potentially harmful enteric microorganisms, viruses, and parasites by the polarized fully differentiated epithelial cells that make up the epithelium, providing a physical and functional barrier. Enterovirulent bacteria interact with the epithelial polarized cells lining the intestinal barrier, and some invade the cells. A better understanding of the cross talk between enterovirulent bacteria and the polarized intestinal cells has resulted in the identification of essential enterovirulent bacterial structures and virulence gene products playing pivotal roles in pathogenesis. Cultured animal cell lines and cultured human nonintestinal, undifferentiated epithelial cells have been extensively used for understanding the mechanisms by which some human enterovirulent bacteria induce intestinal disorders. Human colon carcinoma cell lines which are able to express in culture the functional and structural characteristics of mature enterocytes and goblet cells have been established, mimicking structurally and functionally an intestinal epithelial barrier. Moreover, Caco-2-derived M-like cells have been established, mimicking the bacterial capture property of M cells of Peyer's patches. This review intends to analyze the cellular and molecular mechanisms of pathogenesis of human enterovirulent bacteria observed in infected cultured human colon carcinoma enterocyte-like HT-29 subpopulations, enterocyte-like Caco-2 and clone cells, the colonic T84 cell line, HT-29 mucus-secreting cell subpopulations, and Caco-2-derived M-like cells, including cell association, cell entry, intracellular lifestyle, structural lesions at the brush border, functional lesions in enterocytes and goblet cells, functional and structural lesions at the junctional domain, and host cellular defense responses.

Fine-mapping the genetic association of the major histocompatibility complex in multiple sclerosis: HLA and non-HLA effects

The major histocompatibility complex (MHC) region is strongly associated with multiple sclerosis (MS) susceptibility. HLA-DRB1*15:01 has the strongest effect, and several other alleles have been reported at different levels of validation. Using SNP data from genome-wide studies, we imputed and tested classical alleles and amino acid polymorphisms in 8 classical human leukocyte antigen (HLA) genes in 5,091 cases and 9,595 controls. We identified 11 statistically independent effects overall: 6 HLA-DRB1 and one DPB1 alleles in class II, one HLA-A and two B alleles in class I, and one signal in a region spanning from MICB to LST1. This genomic segment does not contain any HLA class I or II genes and provides robust evidence for the involvement of a non-HLA risk allele within the MHC. Interestingly, this region contains the TNF gene, the cognate ligand of the well-validated TNFRSF1A MS susceptibility gene. The classical HLA effects can be explained to some extent by polymorphic amino acid positions in the peptide-binding grooves. This study dissects the independent effects in the MHC, a critical region for MS susceptibility that harbors multiple risk alleles.

Association study of MICA-TM polymorphism with inflammatory bowel disease in the South Tunisian population

BACKGROUND

Crohn's disease (CD) and ulcerative colitis (UC) are chronic inflammatory disorders of the gastro-intestinal tract with unknown etiology. Both environmental and genetic factors are involved in the pathogenesis of these inflammatory bowel diseases (IBD).

AIM

The purpose of the present study was to determine the association between the polymorphism of the transmembrane region of MICA (MICA-TM), and the genetic susceptibility in Tunisian patients with IBD.

PATIENTS AND METHODS

A total of 102 Tunisian patients (66 with UC, 36 with CD) and 123 healthy controls were enrolled in our study. MICA-TM was genotyped by a semiautomatic fluorescent-labelled PCR method, amplicons were analysed on an ABI Prism 310 genotyper. Comparisons of allele frequencies between patients and controls, and between patients' subgroups were performed using SPSS 13.0.

RESULTS

No MICA allele was significantly increased in both groups of IBD compared to controls. The MICA-A5.1 allele was significantly decreased in CD patients (p=0.006, pc=0.03). In UC, MICA-A6 was associated with the presence of extraintestinal manifestations (p=0.04, pc=0.2), whereas MICA-A5 was associated with late age of onset (p=0.04). In CD, MICA-A6 was significantly increased in active disease patients when compared to moderately active or inactive disease (p=0.03, pc=0.15).

CONCLUSION

Some clinical features of CD and UC may be influenced by specific MICA-TM alleles. In our South Tunisian population, MICA plays a disease modifying role, rather than being an important gene in the susceptibility for developing IBD.

Elevation of soluble major histocompatibility complex class I related chain A protein in malignant and infectious diseases in Chinese patients

Background

Elevation of soluble major histocompatibility complex class I chain-related gene A (sMICA) products in serum has been linked to tissue/organ transplantation, autoimmune diseases and some malignant disorders. Cells infected by microbiological pathogens may release sMICA, whereas less is known whether and to what extent serum sMICA levels may change in infectious diseases.

Methods

The present study determined serum sMICA levels by enzyme-linked immunosorbent assay (ELISA) in a southern China population, including patients (n = 1041) suffering from several types of malignant and infectious diseases and healthy controls (n = 141).

Results

Relative to controls, serum sMICA elevation was significant in patients of hepatic cancer, and was approaching statistical significance in patients with lung, gastric and nasopharyngeal cancers. sMICA elevation was also associated with some bacterial (Enterobacteriaceae, Mycobacterium tuberculosis, non-fermenting Gram-negative bacteria and Gram-positive cocci), viral (hepatitis B and C) and the Microspironema pallidum infections.

Conclusion

Serum sMICA levels may be informative for the diagnosis of some malignant and infectious diseases. The results also indicate that microbiological infections should be considered as a potential confounding clinical condition causing serum sMICA elevation while using this test to evaluate the status of other disorders, such as cancers, host-graft response and autoimmune diseases.

Genetic polymorphisms of CYP2D6 oxidation in patients with inflammatory bowel disease

Inflammatory bowel disease (IBD) consists of ulcerative colitis and Crohn's disease, both of which are associated with increased colorectal cancer risk. The relationship between genetically determined polymorphic metabolism of exogenous substances by oxidation catalyzed by CYP2D6 isoenzyme and susceptibility to cancer has aroused great interest. We determined whether there was an association between susceptibility to inflammatory bowel disease and particularly to CYP2D6 genotypes. The study was carried out in 39 patients with IBD. The control group consisted of 129 healthy volunteers. The CYP2D6 genotypes were analyzed by polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) method with DNA extracted from peripheral blood. Among 39 patients with inflammatory bowel disease, extensive metabolizer (EM) genotype constituted 97.4%. One patient (2.6%) was poor metabolizer with CYP2D6*4/CYP2D6*4 genotype. Results obtained in the inflammatory bowel disease group did not differ significantly from those of the control group. Although the odds ratio for EM metabolizers was about 3.8-fold greater in the group of patients with inflammatory bowel disease, this association was not statistically significant. This data also showed no overall statistically significant association between alleles and incidence risk of inflammatory bowel disease [odds ratio (OR) of 1.36 for CYP2D6*1 allele, 0.83 for CYP2D6*3 allele, and 0.74 for CYP2D6*4 allele]. The present results suggest that EM genotype may be the risk factor of inflammatory bowel disease. Future studies are needed to confirm our assumptions on larger group of patients.

Association analysis of MICA gene polymorphism and MICA-129 dimorphism with inflammatory bowel disease susceptibility in a Spanish population

MICA is located at 46 kb centromeric of HLA-B, is highly polymorphic and interactions with NKG2D, its receptor on the surface of NK, Tgammadelta, and T CD8 lymphocytes. A variation at amino acid position 129 of the alpha2-heavy chain domain seems to categorize MICA alleles into strong and weak binder of NKG2D receptor, and thereby to influence effector cell function. Our aim was to study allele polymorphism of MICA and the functionally relevant dimorphism (129val/met) of MICA gene in inflammatory bowel disease (IBD) patients in our population. DNA was obtained from IBD patients (n = 88) and unrelated healthy Murcians (n = 154) and used to MICA genotyping using polymerase chain reaction-sequence-specific oligonucleotides. We did not find statistical differences in the distribution of MICA alleles between the IBD and control groups. However, we found a higher frequency of MICA-129met/met and a lower frequency of MICA-129val/met genotypes in IBD patients (mainly in ulcerative colitis) than in controls (pc = 0.02). These preliminary data could suggest a relevant role of MICA-129-val/met SNP (weak/strong binders of NKG2D receptor) in the pathogenesis of IBD.

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.

Research progress in susceptible genes of inflammatory bowel disease

The mechanism of inflammatory bowel disease (IBD) is partially understood, but it is certain that a genetic predisposition, through the inheritance of a number of contributory genetic polymorphisms, contributes to the pathogenesis of IBD. These variant forms of genes may be associated with an abnormal response to normal luminal bacteria. Those genes that have been consistently associated with IBD thus far primarily fall into one of three classes: those affecting bacterial recognition, those affecting immune response, and a third group affecting mucosal transport polarity or mucosal transporter function. This article reviews the IBD related genes mentioned above.

Association of MICA-TM and MICB C1_2_A microsatellite polymorphisms with tumor progression in patients with colorectal cancer

Purpose

The major histocompatibility complex class I related A (MICA) and MICB molecules are ligands of NKG2D receptors on natural killer cells, gamma/delta T cells, and CD8aß T cells that mediate host antitumor immune response. The role of MICA-TM and MICB C1_2_A alleles in patients with colorectal cancer has not yet been investigated.

Methods

We have analyzed the MICA-TM and MICB C1_2_A polymorphisms in colorectal cancer patients (n = 79) by polymerase chain reaction amplification, subsequent electrophoresis, and sequencing in comparison to a previously analyzed cohort of healthy controls (n = 306). Allele frequencies obtained for MICA-TM and MICB C1_2_A were compared to histopathological data regarding tumor invasion, disease progression, microsatellite instability, and the presence of KRAS mutations (codon 12) and analyzed for possible impact on tumor-related survival (n = 61).

Results

Allele frequencies of MICA-TM and MICB C1_2_A polymorphisms were not different in patients with colorectal cancer in comparison to normal controls. In colorectal cancer patients, MICA-TM A4 allele was directly and MICA-TM A5 allele was inversely associated with lymph node involvement and advanced UICC stages. Tumor-related survival in colorectal cancer patients was significantly reduced in the presence of the MICA-TM A4 allele (p = 0.015). In patients with microsatellite stable tumors, survival was reduced in association with the MICA-TM A4 allele (p = 0.006) and MICA-TM A9 allele (p = 0.034), but increased in patients showing the MICA-TM A5 allele (p = 0.042).

Conclusions

Specific MICA-TM alleles seem to influence tumor progression and midterm survival of patients with colorectal cancer, indicating an important role of host innate immune predisposition involving NKG2D mediated antitumor response.

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.

Inhibition of NKG2D receptor function by antibody therapy attenuates transfer-induced colitis in SCID mice

A role for the activating NK-receptor NKG2D has been indicated in several autoimmune diseases in humans and in animal models of type 1 diabetes and multiple sclerosis, and treatment with monoclonal antibodies to NKG2D attenuated disease severity in these models. In an adoptive transfer-induced model of colitis, we found a significantly higher frequency of CD4(+)NKG2D(+) cells in blood, mesenteric lymph nodes, colon, and spleen from colitic mice compared to BALB/c donor-mice. We, therefore, wanted to study the effect of anti-NKG2D antibody (CX5) treatment initiated either before onset of colitis, when the colitis was mild, or when severe colitis was established. CX5 treatment decreased the detectable levels of cell-surface NKG2D and prophylactic administration of CX5 attenuated the development of colitis significantly, whereas a more moderate reduction in the severity of disease was observed after CX5 administration to mildly colitic animals. CX5 did not attenuate severe colitis. We conclude that the frequency of CD4(+)NKG2D(+) cells increase during development of experimental colitis. NKG2D may play a role in the early stages of colitis in this model, since early administration of CX5 attenuated disease severity.

Genes, diet and inflammatory bowel disease

Inflammatory bowel disease (IBD) arises in part from a genetic predisposition, through the inheritance of a number of contributory genetic polymorphisms. These variant forms of genes may be associated with an abnormal response to normal luminal bacteria. A consistent observation across most populations is that any of three polymorphisms of the Caspase-activated recruitment domain (CARD15) gene are more prevalent in IBD patients as compared with unaffected controls. Similar aberrant responses to bacteria are associated with variants in Autophagy-related 16-like 1 (ATG16L1) and human defensin (HBD-2, -3 and -4) genes. The defective bacterial signal in turn leads to an excessive immune response, presenting as chronic gut inflammation in susceptible individuals. Inconsistent population reports implicate the major histocompatability complex (MHC), that encodes a number of human leukocyte antigens (HLA), MHC class I chain-related gene A (MICA) or cytokines, such as tumour necrosis factor-alpha (TNF-alpha). Toll-like receptors encoded by the TLR4 or TLR9 genes may also play a role. Recent whole genome scans suggest that a rare variant in the interleukin-23 receptor (IL23R) gene may actually protect against IBD. Other implicated genes may affect mucosal cell polarity (Drosophila discs large homologue 5, DLG5) or mucosal transporter function (sodium dependent organic cation transporters, SLC22A4 and SLC22A5). A variant in ABCB1 (ATP-binding cassette subfamily B member 1) may be especially associated with increased risk of UC. While pharmacogenetics is increasingly being used to predict and optimise clinical response to therapy, nutrigenetics may have even greater potential. In many cases, IBD can be controlled through prescribing an elemental diet, which appears to act through modulating cytokine response and changing the gut microbiota. More generally, no single group of dietary items is beneficial or detrimental to all patients, and elimination diets have been used to individualise dietary requirements. However, recognising the nature of the genes involved may suggest a more strategic approach. Pro- or prebiotics will directly influence the microbial flora, while immunonutrition, including omega-3 fatty acids and certain polyphenols, may reduce the symptoms of gut inflammation. The expression of gut transporters may be modulated through various herbal remedies including green tea polyphenols. Such approaches would require that the gene of interest is functioning normally, other than its expression being up or down-regulated. However, new approaches are being developed to overcome the effects of polymorphisms that affect the function of a gene. A combination of human correlation studies with experimental models could provide a rational strategy for optimising nutrigenetic approaches to IBD.

Crohn's disease and polymorphism of heat shock protein gene HSP70-2 in the Tunisian population

BACKGROUND AND AIMS

Crohn's disease is a multifactorial disorder with a pivotal role of the genetic component. HSP70-2 gene, located in IBD3 region, has a PstI polymorphic site associated recently with Crohn's disease especially with a perforating form. In this study, we sought to determine whether this polymorphism was associated with Crohn's disease in the Tunisian population and its correlation with clinical manifestation of the disease.

METHODS

In all, 148 patients with Crohn's disease and 81 healthy individuals were genotyped for the HSP70-2 PstI polymorphism by restriction fragment length polymorphism analysis.

RESULTS

The allele and genotype frequency of the PstI polymorphism did not differ between patients and controls. Furthermore, this polymorphism was not associated with specific disease behavior.

CONCLUSION

This study reported the absence of association between Crohn's disease and HSP70-2 gene in the Tunisian population. The allele A of PstI polymorphism was not associated with phenotype of the disease.

Killer Ig-like receptor (KIR) genotype and HLA ligand combinations in ulcerative colitis susceptibility

Killer immunoglobulin-like receptors (KIRs) are expressed on natural killer cells and some T-cell subsets and produce either activation or inhibitory signals upon binding with the appropriate human leucocyte antigen (HLA) ligand on target cells. Recent genetic association studies have implicated KIR genotype in the development of several inflammatory conditions. Ulcerative colitis (UC) is an inflammatory disorder of the colonic mucosa that results from an inappropriate activation of the immune system driven by host bacterial flora. We developed a polymerase chain reaction-sequence specific primer (SSP)-based assay to genotype 194 UC patients and 216 control individuals for 14 KIR genes, the HLA-Cw ligand epitopes of the KIR2D receptors and a polymorphism of the lectin-like-activating receptor NKG2D. Initial analysis found the phenotype frequency of KIR2DL2 and -2DS2 to be significantly increased in the UC cohort (P=0.030 and 0.038, respectively). Logistic regression analysis revealed a protective effect conferred by KIR2DL3 in the presence of its ligand HLA-Cw group 1 (P=0.019). These results suggest that KIR genotype and HLA ligand interaction may contribute to the genetic susceptibility of UC.

Genetic variants and the risk of Crohn's disease: what does it mean for future disease management?

Genetic research in inflammatory bowel disease, especially in Crohn's disease, has made significant progress during recent years. There have been > 10 total genome scans that have been performed, and susceptibility loci on several chromosomes have been identified. Together with candidate gene studies, these scans have led to the identification of several susceptibility genes, with CARD15 being the most important. These genetic data have already provided important insights into the pathophysiology of inflammatory bowel disease and are stimulating future research. On the other hand, genotype-phenotype associations have illustrated the heterogenic nature of the disease. Although the clinical application of this knowledge is so far limited, there is significant optimism that an individual management of patients based on genetic data will be possible in the near future.

Genetics of inflammatory bowel disease: The role of the HLA complex

The human leucocyte antigen (HLA) complex on chromosome 6p21.3 is the most extensively studied genetic region in Inflammatory bowel disease (IBD). Consistent evidence of linkage to IBD3 (6p21.1-23), an area which encompasses the HLA complex, has been demonstrated for both Crohn’s disease and ulcerative colitis, and a number of replicated associations with disease susceptibility and phenotype have recently emerged. However, despite these efforts the HLA susceptibility gene (s) for IBD remain elusive, a consequence of strong linkage disequilibrium, extensive polymorphism and high gene density across this region. This article reviews current knowledge of the role of HLA complex genes in IBD susceptibility and phenotype, and discusses the factors currently limiting the translation of this knowledge to clinical practice.

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.

Association of an Extended Haplotype of HLA Class I Alleles and Their Flanking Microsatellites with Spondyloarthropathies in South Indian Patients

Spondyloarthropathy (SpA) is a complex autoimmune disease known to have an association with the HLA system. The aims of the present study were to compare the suballelic association of HLA-B27 and other HLA class I genes with microsatellite markers spanning the HLA class I region in the South Indian population of Kerala. The five microsatellites were C1_2_A (D6S2793), C1_2_5 (D6S2811), C1_4_1 (D6S2927), MIB (D6S2810), and STR-MICA. HLA typing was performed in 67 SpA patients and 77 ethnically matched healthy controls by polymerase chain reaction using sequence-specific primers, whereas fluorescence-labeled microsatellites were analyzed using GeneScan analysis. There was a significant association of HLA-B27 and Cw*02 with SpA, whereas B*44 had a negative association with the disease. Only two HLA-B27 subtypes, B*2704 and B*2705, were observed in the South Indian population. We were able to successfully predict the major B27 subtype B*2705 based on the C1_2_5 microsatellite. A significant association of different alleles of all the microsatellite markers with SpA was observed. An extended six-locus haplotype, B*2705-Cw*02-STR-MICA(A4)-C1_4_1 (213 bp)-C1_2_5 (178 bp)-MIB (340 bp), was significantly associated with SpA.

MHC class I chain-related gene A-A5.1 allele is associated with ulcerative colitis in Chinese population

The human MHC class I chain-related gene A (MICA) plays a role in regulating protective responses by intestinal epithelial Vdelta1 gamma delta T cells and the polymorphism of MICA were reported to be related to several autoimmune diseases. The present study aimed to investigate the association of the microsatellite polymorphisms of TM region of MICA gene with the susceptibility to ulcerative colitis (UC) in Chinese population. The microsatellite polymorphisms of the MICA were genotyped in unrelated 86 Chinese patients with UC and 172 ethnically matched healthy controls by a semiautomatic fluorenscently labelled PCR method. All the subjects were the Chinese with Han nationality. The frequency of MICA-A5.1 homozygous genotype and A5.1 allele were significantly increased in UC patients compared with healthy controls (22.1%versus 7%, P = 0.0009, Pc = 0.0126, OR = 3.781, 95%CI: 1.738-8.225 and 30.2%versus 17.4%, P = 0.0014, Pc = 0.007, OR = 2.051, 95%CI: 1.336-3.148, respectively). Adjusted the effects of gender and age at onset, MICA-A5.1 homozygous genotype and A5.1 allele were also increased in the UC patients. Moreover MICA-A5.1 allele was significantly increased in frequency in the female UC patients (38.2%versus 21.0%, P = 0.0095, Pc = 0.0475, OR = 2.326, 95%CI: 1.234-4.382). Logistic regression analysis also revealed that gender was independently associated with UC patients carried MICA-A5.1 allele (P = 0.046, OR (male) = 0.511, 95% CI: 0.264-0.987). Although the UC patients with extensive colitis (32.5%versus 17.4% in the healthy controls, P = 0.005, Pc = 0.025) and the UC patients with extraintestinal manifestations (36%versus 17.4% in the healthy controls, P = 0.0039, Pc = 0.0195) were more likely to carry the MICA-A5.1 allele, EIMs was associated with extent of disease (P < 0.0001, OR (with EIMs) = 3.511, 95% CI 1.747-7.056) and MICA-A5.1 allele was not associated with UC patients with extensive colitis or with EIMs in the logistic regression analysis. Therefore, the MICA-A5.1 homozygous genotype and A5.1 allele were closely associated with UC and the MICA-A5.1 allele was positively associated with the female UC patients in Chinese population.

MIC and other NKG2D ligands: from none to too many

NKG2D, a prime activatory receptor on human NK, CD8(+) alphabeta and gammadelta cells, has a variety of ligands, which, despite sharing membership of the MHC class I structural club, display an array of unique features. Chronologically, human MIC molecules were the first NKG2D ligands to be identified. Then came RAET1 (ULBP) molecules, which were identified in both man and mouse, as well as H60 and MULT1, which have no counterparts in man to date. The question remains as to why, more than how, the evolutionary conserved, apparently monomorphic, single copy, NKG2D, can/should adapt to this variety of ligands, and when it does, what is the evolutionary advantage of this profusion of ligands for a single receptor?

Pathogenesis of Afa/Dr diffusely adhering Escherichia coli

Over the last few years, dramatic increases in our knowledge about diffusely adhering Escherichia coli (DAEC) pathogenesis have taken place. The typical class of DAEC includes E. coli strains harboring AfaE-I, AfaE-II, AfaE-III, AfaE-V, Dr, Dr-II, F1845, and NFA-I adhesins (Afa/Dr DAEC); these strains (i) have an identical genetic organization and (ii) allow binding to human decay-accelerating factor (DAF) (Afa/Dr(DAF) subclass) or carcinoembryonic antigen (CEA) (Afa/Dr(CEA) subclass). The atypical class of DAEC includes two subclasses of strains; the atypical subclass 1 includes E. coli strains that express AfaE-VII, AfaE-VIII, AAF-I, AAF-II, and AAF-III adhesins, which (i) have an identical genetic organization and (ii) do not bind to human DAF, and the atypical subclass 2 includes E. coli strains that harbor Afa/Dr adhesins or others adhesins promoting diffuse adhesion, together with pathogenicity islands such as the LEE pathogenicity island (DA-EPEC). In this review, the focus is on Afa/Dr DAEC strains that have been found to be associated with urinary tract infections and with enteric infection. The review aims to provide a broad overview and update of the virulence aspects of these intriguing pathogens. Epidemiological studies, diagnostic techniques, characteristic molecular features of Afa/Dr operons, and the respective role of Afa/Dr adhesins and invasins in pathogenesis are described. Following the recognition of membrane-bound receptors, including type IV collagen, DAF, CEACAM1, CEA, and CEACAM6, by Afa/Dr adhesins, activation of signal transduction pathways leads to structural and functional injuries at brush border and junctional domains and to proinflammatory responses in polarized intestinal cells. In addition, uropathogenic Afa/Dr DAEC strains, following recognition of beta(1) integrin as a receptor, enter epithelial cells by a zipper-like, raft- and microtubule-dependent mechanism. Finally, the presence of other, unknown virulence factors and the way that an Afa/Dr DAEC strain emerges from the human intestinal microbiota as a "silent pathogen" are discussed.

Major histocompatibility complex class I chain-related gene A in Thai psoriasis patients: MICA association as a part of human leukocyte antigen-B-Cw haplotypes

Psoriasis is a chronic inflammatory skin disorder. Although the aetiology and pathogenesis of psoriasis are unproven, it is hypothesised that the major histocompatibility complex (MHC) gene/haplotype contributes to the susceptibility of psoriasis in many populations. MHC class I chain-related gene A (MICA), located 46-kb centromeric of HLA-B, is expressed on keratinocytes and fibroblasts. MICA is in linkage disequilibrium with HLA-B and is involved in natural killer-cell functions. To investigate the relative contribution of the MICA gene in the pathogenesis of psoriasis, extracellular polymorphisms of MICA were studied by polymerase chain reaction-sequence specific primers in 128 Thai psoriasis patients (87 and 41 were Types I and II, respectively) from Srinagarind Hospital, Faculty of Medicine, Khon Kaen University. The control group included 255 healthy, unrelated Northeast Thais. We observed 11 MICA alleles (or groups of alleles) in the patients. A comparison of the psoriasis patients and the control group revealed that MICA*010 and MICA*017 were associated with Type I psoriasis whereas only MICA*010 was associated with Type II. The haplotype analysis revealed that MICA*008-HLA-B*13-Cw*0602 and MICA*010-HLA-B*4601-Cw*01 were significantly increased in both Types I and II, whereas MICA*002-HLA-B*38-Cw*07 (01-03) and MICA*017-HLA-B*57-Cw*0602 were elevated only in Type I. MICA*010 was in strong linkage with Cw*01. Analysis of independent association of MICA*010 in individuals lacking Cw*01 failed to maintain an association. Our results suggest that a significant increase of the MICA alleles in the patient group is a part of HLA-B-Cw haplotypes. It is conceivable that an unknown susceptibility gene, on certain HLA-B-Cw haplotypes, is responsible for the development of psoriasis.

The contribution of human leucocyte antigen complex genes to disease phenotype in ulcerative colitis

Linkage and association studies implicate the human leucocyte antigen (HLA) region in genetic susceptibility to ulcerative colitis (UC). However, associations with specific variants have been inconsistent, even within defined ethnic groups. A genetic basis for the disease heterogeneity of UC may account for these discrepant findings from studies in unselected populations. Here, we examine the contribution of the HLA region to the clinical phenotype of UC. We studied 321 accurately phenotyped patients recruited from a single UK centre, with a median follow-up time of 15 years. Individuals were genotyped for 340 polymorphisms constructed into 25 gene-specific allelic haplotypes between HLA-A and Tapasin. Data were analysed with respect to age of onset, disease extent and severity. Strongest association with overall susceptibility was identified with HLA-DRB1 alleles replicating previous studies (DRB1*0103, DRB1*1502 and DRB1*0401). We report a novel association with homozygosity of a tumour necrosis factor (TNF) promoter haplotype (TNF-1031T, -863C, -857C, -380G, -308G and -238G) and distal disease extent that does not extend with time (distal vs total 40.9 vs 25.7%; RR = 2.0; 95% CI 1.23-3.24). We confirm the association of DRB1*0103 with total disease and/or disease requiring colectomy and further demonstrate that DRB1*0103 is associated with shorter time to surgery. Genes in the HLA play a role in modifying disease phenotype. Further studies are required to dissect how these genes functionally interact with each other and with environmental factors to determine clinical patterns of disease

MICA, HLA-B haplotypic variation in five population groups of sub-Saharan African ancestry

The human major histocompatibility complex (MHC) class I chain-related gene A (MICA), located 46 kb centromeric to HLA-B, encodes a stress-inducible protein, which is a ligand for the NKG2D receptor. In addition to its primary role in immune surveillance, data suggest that MICA is involved in the immune response to transplants and in susceptibility to some diseases. In this study, 152 subjects from the Yoruba (n=74), Efik (n=32), and Igbo (n=46) tribes of southern Nigeria, 39 nationwide African-American stem cell donors, and 60 African-American individuals residing in the metropolitan Boston area were studied for MICA, HLA-B allelic variation, haplotypic diversity, and linkage disequilibrium (LD). MICA and HLA-B exhibited a high degree of genetic diversity among the populations studied. In particular, MICA allele and HLA-B-MICA haplotype frequencies and LD in the Efik and Igbo tribes were significantly different from the other study groups. HLA-B and MICA loci demonstrated significant global LD in all five populations (P-values &<0.00001). LD also varied in a haplotype-specific manner. A novel MICA allele was detected in the Boston population. These findings are important from an anthropologic perspective, and will inform future HLA-linked disease association studies in related ethnic groups of African-derived ancestry.

The contribution of HLA genes to IBD susceptibility and phenotype

The human leukocyte antigen (HLA) region located on chromosome 6p encodes the highly polymorphic, classical class I and II genes essential for normal lymphocyte function; it also encodes a further 224 genes. Many early studies investigating this region were limited by small sample size, poor statistical methodology, population stratification and variable disease definition. Although more recent studies have improved study design, investigators are still challenged by the complex patterns of linkage disequilibrium across this gene-dense region, and by the disease heterogeneity characteristic of all genetically complex disorders. However, a number of important observations have emerged from recent studies: (1) the HLA harbours gene(s) that determine susceptibility to colonic inflammation in both ulcerative colitis (UC) and Crohn's disease (CD); (2) most of the specific associations with UC and CD appear to differ; (3) associations between different ethnic groups differ; (4) markers in the HLA might predict the course of disease and the development of complications, notably the extraintestinal manifestations of disease.

Familial occurrence of inflammatory bowel disease in celiac disease

BACKGROUND

The authors have previously reported a possible increased risk of the familial occurrence of Crohn's disease in patients with celiac disease.

AIM

The aim of the current study was to evaluate in a case-control study the familial occurrence of inflammatory bowel disease (IBD) in first-degree relatives of patients with celiac disease.

METHODS

One hundred eleven consecutive patients with biopsy-proven celiac disease were interviewed to ascertain whether IBD was present in first-degree relatives. The number of relatives, their ages, and possible IBD status were collected in a questionnaire. When a diagnosis of familial IBD was reported, the diagnosis was checked in the hospital records. Two hundred twenty-two controls matched for age and sex (111 from the general population and 111 from orthopedic wards) were also interviewed regarding the possible occurrence of IBD in first-degree relatives. The chi2 test was used to evaluate the difference in proportion of familial occurrence of IBD among individuals with celiac disease and controls.

RESULTS

Among 600 first-degree relatives of patients with celiac disease, 10 cases of IBD were identified among first-degree relatives (7 cases of ulcerative colitis and 3 cases of Crohn's disease), whereas only 1 case of IBD was identified among the 1,196 first-degree relatives of control patients (p < 0.01). When ulcerative colitis and Crohn's disease were analyzed separately, only the prevalence of ulcerative colitis was statistically significant (p </= 0.02).

CONCLUSIONS

This case-control study shows that there is a significantly increased prevalence of familial ulcerative colitis in patients with celiac disease. There was no significant increase in the prevalence of Crohn's disease in patients with celiac disease. The possible role of this association is discussed.

Absence of Mycobacterium avium subspecies paratuberculosis components from Crohn's disease intestinal biopsy tissues

BACKGROUND

Crohn's disease is a chronic human intestinal inflammatory disorder for which an etiologic agent has not been identified. Johne's disease is a similar chronic enteric granulomatous disease of ruminant species and has been used as a model of Crohn's disease. Johne's disease has been proven to be caused by Mycobacterium avium subspecies paratuberculosis (M. avium ss paratuberculosis). It has been proposed that M. avium ss paratuberculosis may also cause Crohn's disease. This is of particular concern because the organism may be spread to humans through inadequately pasteurized dairy products.

OBJECTIVE

We sought to determine whether M. avium ss paratuberculosis could be detected using identical techniques in paraffin-embedded tissue samples of bovine Johne's disease and human Crohn's, ulcerative colitis and diverticular diseases. Samples were obtained for analysis from national tissue banks.

DESIGN

Cross-species and cross-disease sample comparisons by multiple detection techniques.

METHODS

Histology, immunocytochemistry and polymerase chain reaction (PCR) were utilized to test and compare the presence of M. avium ss paratuberculosis components. Insertion sequence IS900, present in multiple copies and found only in M. avium ss paratuberculosis, was utilized in both PCR and immunocytochemical analyses.

RESULTS

The IS900 sequence was demonstrable in all samples of confirmed positive Johne's disease tissue. The sequence was not identified in the 35 Crohn's, 36 ulcerative colitis, and 21 diverticular disease samples.

CONCLUSION

M. avium ss paratuberculosis was not associated with the lesions in these Crohn's disease samples, using these methods.

In vivo immunogenetics: from MIC to RAET1 loci

The major histocompatibility complex (MHC) comprises approximately one thousandth of the genome and encompasses its most polymorphic members. This diversity enables the MHC, at the population level, to counteract the extraordinarily diverse microbiological threats. Reviewed here are two separate sets of MHC class I genes: MIC and RAET1. Whilst the former are encoded within the MHC (6p21.3), the latter are located on the opposite arm of the same chromosome (6q24.2-q25.3). Differing from the prototypical class I genes in structure, transcription, diversity and potential function, they both exemplify the versatility of the MHC fold, despite convergence onto a single ligand, the activatory C-type lectin-like receptor, NKG2D. Why the immune system uses two distinct gene families to interact with a unique ligand remains a fascinating question. To answer this question, the reader will be chronologically exposed to the field whilst following a single thread, i.e. genomics and gene diversity.

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.

Anterior uveitis: current concepts of pathogenesis and interactions with the spondyloarthropathies

Anterior uveitis describes inflammation that involves the iris or ciliary body. Anterior uveitis may be part of a systemic illness such as a spondyloarthropathy. It may also arise from an infection such as herpes simplex; be part of an ocular syndrome, such as Fuchs' heterochromic iridocyclitis; be part of trauma, as in cataract surgery; or result from an idiopathic eye disease with a presumed immune pathogenesis. During 2001, progress has been made understanding uveitis in general, as well as specifically, in association with spondyloarthropathy. Here, we review recent insights into anterior uveitis with regard to clinical presentation, immune mechanisms, genetics, and anti-tumor necrosis factor therapy.