B-cell numbers in the blood of patients with non-HLA*B8 or non-HLA*B44 common variable immunodeficiency.

BACKGROUND: Genetic susceptibility to common variable immunodeficiency (CVID) has been linked to the inheritance of part or all of 2 extended major histocompatibility complex haplotypes: HLA*B8*DR3(17) and HLA*B44*DR7. OBJECTIVE: To determine whether the inheritance of these major histocompatibility complex susceptibility haplotypes correlates with absolute B-cell numbers. METHODS: A retrospective medical record review of 55 consecutive patients with CVID whose blood was analyzed for B-cell numbers using a fluorescent-activated cell sorter. RESULTS: The mean +/- SD absolute count of CD19+ B cells among the 36 patients (65%) with CVID who had inherited HLA*B8 or HLA*B44 was 218 +/- 23 cells/mm3 compared with 119 +/- 27 cells/mm3 in those who had not inherited HLA*B8 or HLA*B44 (P = .008). There were no significant differences in B-cell numbers among the 33 patients (60%) with CVID who had inherited HLA*DR7 or HLA*DR3(17) and those who had not. CONCLUSIONS: Patients with CVID who inherited HLA*B44 or HLA*B8 tended to have higher numbers of B cells in the blood than those who did not, suggesting that the mechanism of immunodeficiency may differ.     

The HLA DQB 1*0502 allele is neutrally associated with insulin-dependent diabetes mellitus in the Sardinian population

In the Sardinian population a very high incidence of insulin-dependent diabetes mellitus (IDDM) and the lack of HLA-DR2 protective effect due to the high frequency of the A2, Cw7, B17, 3F31, DR2, DQw1 extended haplotype has been reported. This haplotype, carrying a Serine at position 57 of the DQB1*0502 allele, has been previously reported to be underrepresented in patients when compared to controls. In order to provide an explanation for this finding, we defined by RFLP analysis the HLA haplotype of 45 Sardinian IDDM patients and 49 controls. All DR-2DQw1 subjects were molecularly characterized at the HLA DQA and DQB loci. All DR2-positive patients and the vast majority of the DR2-positive controls had the DQB1*0502 allele at the DR2-linked DQB1 locus, with no statistically significant difference between the two groups. All DQA1 genes were the ones expected, with only two exceptions. Nine out of 10 of the DR2-positive patients were compound heterozygotes for DQB1*0201/DQB1*0502 alleles; only this allele combination was significantly increased (p less than 0.0003). Our data suggests that a) the DQB1*0502 allele is neutral for IDDM development and b) the susceptibility to IDDM in our DR2-positive patients is related to the compound heterozygous state between the neutral DQA1*0102/DQB1*0502 and the susceptibility DQA1*0501/DQB1*0201 alleles.     

The non‐inherited maternal HLA haplotype affects the risk for type 1 diabetes

The aim was to test the hypothesis that the human leucocyte antigen (HLA) haplotype that is not inherited from the mother, that is, the non‐inherited maternal antigen (NIMA) affects the risk for type 1 diabetes (T1D). A total of 563 children with T1D and 286 non‐diabetic control children from Sweden were genotyped for DRB1, DQA1 and DQB1 alleles. The frequency of positively (DR4‐DQA1*0301‐B1*0302 and DR3‐DQA1*0501‐B1*0201), negatively (DR15‐DQ A1*0102‐B1*0602) or neutrally (all other) T1D associated HLA haplotypes were compared between NIMA and non‐inherited paternal antigen (NIPA). All comparisons were carried out between HLA‐matched patients and controls. The frequency of positively associated NIMA was higher among both DR4/X‐positive healthy individuals compared wit DR4/X‐positive patients (P < 0.00003) and DR3/X‐positive healthy individuals compared with DR3/X‐positive patients (P < 0.009). No such difference was observed for NIPA. High‐risk NIMA was increased compared to NIPA among healthy DR3/X‐ and DR4/X‐positive children (P < 0.05). There was no difference in frequency of positively associated haplotypes between patient NIMA and NIPA. The NIMA but not the NIPA affects the risk for T1D, suggesting that not only the inherited but also non‐inherited maternal HLA haplotypes, perhaps through microchimerism or other mechanisms, may influence the risk for the disease.     

HLA-A, -B, -C, -DR, -DQ typing in a population group of Senegal: distribution of HLA antigens and HLA-DRB1*13 and DRB1*11 subtyping by PCR using sequence-specific primers (PCR-SSP)

One-hundred-and sixteen Senegalese Serere were typed for HLA antigens and compared with other ethnic groups in Gambia. We did not find significant differences (Fisher's exact test; P0.01) in the HLA antigens distribution between the Serere and Mandinka groups in Senegal and the Serere, Mandinka and Wolof in The Gambia. The most common HLA haplotypes found (P0.01; Chi square with Yates' correction) were: A1, B8; A2, B51; A32, B44; A33, B58; A2, Cw2; A2, Cw4; A33, Cw3; A2, DR17; A10, DR10; B35, Cw4; B53, Cw6; B57, Cw3; B65, Cw8; B50, DR15; B52, DR4; Cw2, DR17; DR7, DQ2; DR18, DQ4. The HLA-DRB1*13 and DRB1*11 alleles were subtyped by PCR-SSP and the frequencies of these alleles in the studied population given. HLA-DRB1*1304 and DRB1102 were the most common alleles found respectively 15.0 and 18.5%     

Generation of HLA-B*1516/B*1567/B*1595 and B*1517 alleles (B15 specific group) by transpecies evolution

The generation of the human leukocyte antigen (HLA)–B*1516, B*1517, B*1567, and B*1595 alleles has been analyzed using exon 1, intron 1, exon 2, intron 2, and exon 3 sequences from human and non-human primates. Results showed that at the first place three evolutionary steps would have been necessary for the generation of HLA-B*1516 and B*1517 alleles: (1) a non-human primate step with the generation of a major histocompatibility complex (MHC)–B*1516/1517–like allele; (2) a human or non-human primate step with two different ways of evolution generating a MHC-B*1516 and a MHC-B*1517 ancestors; and (3) a human step consisting of the generation of HLA-B*1516 and HLA-B*15170101 alleles. After that, HLA-B*1567, B*1595 B*151701012, and B*151702 alleles would be generated by point mutation events. In conclusion these alleles are generated by two different evolutionary pathways. The generation of these alleles points out the importance of the exons/introns in the generation of the evolution of HLA alleles.     

Haplospecific polymorphism between HLA B and tumor necrosis factor.

Polymorphisms were sought between HLA B and tumor necrosis factor (TNF) using three genomic probes. Extensive polymorphism was detected within a panel of 50 cell lines including 37 homozygotes representing 21 different ancestral haplotypes (AH). Following Taq I digestion of genomic DNA, we observed three allelic patterns with probe X (R17A) and four with probe V (R9A). Seven different allelic patterns were found with probe Y (M20A) after Taq I + Rsa I digestion. Family studies showed that the Y, X, and V alleles were inherited and segregated with HLA haplotypes. A striking feature of the allelic patterns detected by these probes was that cells with the same AH had identical Y, X, and V alleles (i.e., the alleles were haplotypic). Of 15 different Y-X-V haplotypes observed, 11 were found to be specific for a particular AH (i.e., were haplospecific). Four were shared by more than one AH, but in these instances there were extensive similarities in other regions within the major histocompatibility complex (MHC), for example, the Japanese 46.2 (HLA Bw46-DRw8) and the Chinese 46.1 (Bw46-DR9) share all alleles between HLA C and C4 and differ only in class II, suggesting their relatively recent divergence by recombination between C4 and DR. Surprisingly, two insulin-dependent diabetes mellitus (IDDM)-resistant but race-specific AHs 52.1 (Bw52-DRB1*1502, Japanese) and 7.1 (B7-DRB1*1501, Caucasoid) carry the same Y-X-V haplotype, suggesting the possibility of localizing gene(s) relevant to IDDM. The present study confirms that MHC AHs have been conserved en bloc, including the region between HLA B and TNF.     

Imputation of class I and II HLA loci using high‐density SNPs from ImmunoChip and their associations with Kawasaki disease in family‐based study

Kawasaki disease (KD) is the leading cause of acquired heart disease in children in most developed countries including the United States. The etiology of KD is not known; however, epidemiological and immunological data suggest infectious or immune‐related factors in the manifestation of the disease. Further, KD has several hereditary features that strongly suggest a genetic component to disease pathogenesis. Human leucocyte antigen (HLA) loci have also been reported to be associated with KD, but results have been inconsistent, in part, because of small study samples and varying linkage disequilibrium (LD) patterns observed across different ethnic groups. To maximize the informativeness of single nucleotide polymorphism (SNP) genotypes in the major histocompatibility (MHC) region, we imputed classical HLA I (A, B, C) and HLA II (DRB1, DQA1, DQB1) alleles using SNP2HLA method from genotypes of 6700 SNPs within the extended MHC region contained in the ImmunoChip among 112 White patients with KD and their biological parents from North America and tested their association with KD susceptibility using the transmission disequilibrium test. Mendelian consistency in the trios suggested high accuracy and reliability of the imputed alleles (class I = 97.5%, class II = 96.6%). While several SNPs in the MHC region were individually associated with KD susceptibility, we report over‐transmission of HLA‐C*15 (z = +2.19, P = 0.03) and under‐transmission of HLA‐B*44 (z = ?2.49, P = 0.01) alleles from parents to patients with KD. HLA‐B*44 has been associated with KD in other smaller studies, and both HLA‐C*15 and HLA‐B*44 have biological mechanisms that could potentially be involved in KD pathogenesis. Overall, inferring HLA loci within the same ethnic group, using family‐based information is a powerful approach. However, studies with larger sample sizes are warranted to evaluate the correlations of the strength and directions between the SNPs in MHC region and the imputed HLA alleles with KD.     

DQCAR microsatellite polymorphisms in three selected HLA class II-associated diseases

Abstract: DQCAR is a very polymorphic CA repeat microsatellite located between the HLA DQA1 and DQB1 gene. Previous studies have shown that specific DQCAR alleles are in tight linkage disequilibrium with known HLA DR-DQ haplotypes. Of special interest was the fact that haplotypes containing long CA repeat alleles (DQCAR > 111) were generally more polymorphic within and across ethnic groups. In these latter cases, several DQCAR alleles were found even in haplotypes containing the same flanking DQA1 and DQB1 alleles. In this work, three HLA class II associated diseases were studied using the DQCAR microsatellite. The aim of this study was to test if DQCAR typing could distinguish haplotypes with the same DRB1, DQA1 and DQB1 alleles in control and affected individuals. To do so, patients with selected HLA DR-DQ susceptibility haplotypes were compared with HLA DR and DQ matched controls. This included: Norwegian subjects with Celiac disease and the HLA DRB1*0301, DQA1*05011, DQB1*02 haplotype; Japanese subjects with Type 1 (insulin-dependent) Diabetes Mellitus and the HLA DRB1*0405, DQA 1*0302, DQB 1*0401 haplotype; and French patients with corticosensitive Idiopathic Nephrotic Syndrome and the HLA DRB 1*0701, DQA 1*0201, DQB1*0202 haplotype. These specific haplotypes were selected from our earlier work to include one haplotype bearing a short DQCAR allele (celiac disease and DR3, DQ2-DQCAR99) and two haplotypes bearing long DQCAR alleles (Diabetes Mellitus and DR4, DQ4-DQCAR 113 or 115 Idiopathic Nephrotic syndrome and DR7, DQ2-DQCAR 111–121). Additional DQCAR diversity was found in both control and patients bearing haplotypes with long CA repeat alleles. The results indicate that DQCAR typing did not improve specificity in combination with high resolution DNA HLA typing as a marker for these three disorders.     

HLA class II alleles associated with celiac disease susceptibility in a Southern European population

Susceptibility to celiac disease in Northern Europe is associated with the human leukocyte antigens (HLA) B8, DR3 and DQ2, which exist together on an extended haplotype. The strong predominance of this haplotype within the Northern European celiac populations, together with the linkage disequilibrium which occurs between these loci, does not allow identification of the gene(s) primarily associated with disease susceptibility. Studies from Southern Europe using both serology and examination of restriction fragment length polymorphisms (RFLP) have demonstrated associations with DR3, DR7 and DQ2, suggesting that the DQ locus is primarily involved. We investigated 43 celiac patients and 41 healthy controls from Rome, Italy, using sequence-specific oligonucleotide (SSO) probes, in conjunction with gene amplification by the polymerase chain reaction (PCR), to determine alleles at the DRB, DQA1, DQB1 and DPB1 loci: 19% of celiac patients possessed the alleles DRB1*0301 DRB3*0101, 33% DRB1*0301 DRB3*0201 and 33% of celiac patients were heterozygous for DRB1*1101-1201/DRB1*0701. The strongest association with celiac disease susceptibility was the combination of alleles DQA1*0501 DQB1*0201 (91% celiac patients vs. 12% controls; p = 0.000002). There was no additional susceptibility associated with alleles at the DPB locus. This study confirms the hypothesis that susceptibility is associated with a particular combination of DQ alleles and the ethnic variation in DR frequencies is secondary to linkage disequilibrium with these DQ alleles.     

Molecular genetic studies of HLA class II alleles in sarcoidosis

Abstract: Previous HLA serological studies showed positive associations of the DR52 antigen, the DR52-associated antigens (DR3, DR5 and DR6) and the DR8 antigen with sarcoidosis. To investigate the HLA alleles that may contribute to the genetic susceptibility to sarcoidosis at the DNA level, HLA-DRB1, -DRB3, -DQA1 and DQB1 genotyping using the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method was performed in 63 Japanese patients with sarcoidosis. The frequencies of the DR52-associated DRB1 alleles (DRB1*11, DRB1*12 and DRB1*14 except DRB1*1302), DRB1*08, DRB3*0101, DQA1*0501 and DQB1*0301 were significantly increased in patients compared with healthy controls. The significant increase of DRB3*0101, DQA1*0501 and DQB1*0301 could be explained by linkage disequilibrium with the DR52-associated DRB1 alleles. It must be noted that the DR8 haplotype, which does not possess the DRB3 gene, also showed a significant increase in sarcoidosis. These results suggest that the HLA-alleles responsible for the susceptibility to sarcoidosis are located at the HLA-DRB1 locus rather than the HLA-DRB3, -DQA1 and -DQB1 loci. In contrast, DRB1*1302 may confer resistance to the disease.     

HLA and Autoimmunity in Scleroderma (Systemic Sclerosis)

Scleroderma or systemic sclerosis (SSc) has been associated with certain class II antigens of the major histocompatibility complex (MHC), including HLA-DR1, DR2, DR3, DR5, and DR52. In general, these earlier HLA correlations were weak and varied considerably among reporting centers and different ethnic populations. More recently, a variety of disease-specific autoantibodies have been discovered including anticentromere, anti-topoisomerase I, and a variety of anti-nucleolar antibodies. These specificities show little overlap among one another, and each are markers for certain clinical features of SSc.

At the same time, molecular studies of the MHC have provided more accurate methods for defining specific HLA alleles. Now it is becoming clear that certain HLA class II alleles, especially HLA-DQ, are more strongly associated with autoantibody subsets of SSc than with the disease itself. For example, anticentromere antibodies are strongly associated with HLA-DQB1*0501 (DQ5), DQB1*0301 (DQ7) and other DQB1 alleles possessing a glycine or tyrosine residue in position 26 of the outermost domain. Anti-topoisomerase I antibodies occur in SSc patients with HLA-DQB1*0301 (DQ7), DQB1*0302 (DQ8), DQB1*0601 (DQ6 in Japanese), and other DQB1 alleles possessing a tyrosine residue in position 30. HLA-DQ alleles associated with these autoantibodies tend to be in linkage disequilibrium with the HLA-DR specificities previously associated weakly with SSc itself. Rare multiplex families with SSc also show these same HLA haplotypes co-segregating with autoantibody profiles in affected members. Thus, it appears that MHC alleles play a role in affecting the serological expression of SSc, and the implications of these recent findings are discussed.     

HLA CLASS II AND SUSCEPTIBILITY AND RESISTANCE TO INSULIN-DEPENDENT DIABETES MELLITUS IN A POPULATION FROM THE NORTHWEST OF SPAIN

The role of HLA class II alleles in genetic predisposition to insulin-dependent diabetes mellitus(IDDM) was examined using Polymerase Chain Reaction/oligonucleotide probe typing (PCR/SSOs) of eight HLA class II loci in 58 IDDM patients and 50 healthy controls from the Northwest of Spain (Asturias). We compared the distribution of HLA class II alleles, haplotypes and genotypes between IDDM patients and controls, and tested three recently proposed HLA-IDDM susceptibility theories. By using the aetiologic fraction (δ) as an almost absolute measure of the strongest linkage of disequilibrium of a HLA marker to the putative Type I susceptibility locus, it has been found that the strength of association of the HLA markers may be quantified as follows: DQA1 *03-DQB1 *0302 or DQA1 *0501-DQB1 *0201 > DR3 or DR4; presence of more than one dimer DQαβ of the six proposed by Rønningen > non-Asp57 DQβ and Arg52 DQα > Arg52 DQα > non-Asp57 DQβ/non-Asp57 DQβ > DRB1*0301; DQA1*0501-DQB1*0201 > DQA1*03-DQB1*0302; DQB1*0302. The presence of at least one Asp57 DQβ allele was the best protection HLA marker to IDDM in our population. Therefore, the above data confirm that IDDM susceptibility to HLA locus is linked more to DQ than DR.     

Relationship Between the Reactivity to Hepatitis B Virus Vaccination and the Frequency of MHC Class I, II and III Alleles in Haemodialysis Patients

To study the immunoreactivity genes in a heterogeneous human population needs a large number of individuals. Associations between HLA antigens and immunoresponse to viral or bacterial antigens have been studied with controversial results. As a homogeneous population, the MHC class I, II and III allele distribution was studied in 153 end-stage renal disease patients (ESRD, average duration of renal replacement: 8.2+5.1 years) immunized with a recombinant hepatitis B vaccine in accordance to the standard vaccination schedule. Thirty-four patients with an antibody titre of less than 10 U/l following the last booster injection were considered as non-responders while 119 patients with antibody titre equal to or more than 10 U/l were considered as responders. The responder group was divided into two subgroups: low responders (antibody titre: 1000 U/l) and high responders (antibody titre: > 1000 U/ 1). Marked differences were observed between responders and non-responders in the occurrence of carriers of different MHC class I, II and III alleles. Homozygotes for HLA—A1, HLA—B8, HLA—DR3 and HLA—DQ2 were found almost exclusively in the non-responder group and significantly more heterozygotes for these alleles were found in the non-responder group compared to the responders. Similar albeit less marked differences were found in the frequency of some MHC class III alleles (C4A*6, C4A*QO, Bf*F, BPS0.7). Within the responder group, carriers of HLA—A2, HLA—B7 and HLA—DR4 were found to be clustered in the low responder sub-group whereas carriers of HLA—A1, HLA—B27, HLA—Cw2, C4A*6 and Bf*F were observed more frequently in the group of high responders. Similar differences were found with extended haplotypes as well. For example, the extended haplotypes HLA—Al, B8, BfS, C4AQO, C4B1, DR3, DQ2 and HLA—A1, B8, BfF, C4A6, C4B2, DR3, DQ2 were present in nine of 34 cases of non-responders but only in one of 119 case of responders (P <0.000001). These observations indicate that the presence or absence of certain MHC alleles even in heterozygous form determine the responsiveness to hepatitis B vaccination in end-stage renal disease patients, and among responders, the intensity of antibody response is also markedly influence by immunogenetic factors.     

Association between two tumour necrosis factor intronic polymorphisms and HLA alleles

The gene for tumour necrosis factor (TNF) lies at the telomeric end of the class III region of the major histocompatibility complex (MHC). Polymorphisms within this gene have been implicated in the genetic background of a large number of common human diseases. Recently two polymorphisms, TNF +489 and +691, have been described in the first intron of TNF (+489, G to A transition; +691, G deletion) and disease associations have been reported; however, the pattern of linkage disequilibrium with other MHC alleles has not been studied. We have therefore studied the association of TNF alleles with HLA‐DR, ‐DQ and ‐B alleles in 216 healthy individuals from the north of England. The frequencies of the uncommon alleles were 0.08 (+489A) and 0.05 (+691G^del). The +489A allele is associated with carriage of DRB1*1104, DQB1*0301, B18 and B35. The +691G^del allele is associated with carriage of DRB1*13 *11, DQB1*0301 and B44. Knowledge of the pattern of association, indicating probable linkage disequilibrium, between these TNF alleles may be useful in studies aimed at determining the role of this locus in the genetic background of the large number of diseases which show genetic associations with MHC haplotypes.     

Disease relevant HLA class II alleles isolated by genotypic, haplotypic, and sequence analysis in North American Caucasians with pemphigus vulgaris

Early studies of genetic susceptibility to pemphigus vulgaris (PV) showed associations between human leukocyte antigen (HLA) DR4 and DR6 and disease. The emergence of DNA sequencing techniques has implicated numerous DRB1 and DQB1 loci in various populations, leading to confusion regarding which exact alleles confer susceptibility. The strong linkage disequilibrium among DR and DQ HLA alleles further complicates the investigation of the true susceptibility loci. In this study, we report genotyping data for the largest sampling of North American Caucasian non-Jewish and Ashkenazi Jewish PV patients studied to date and compare our data with other population studies. To pinpoint true susceptibility, alleles among overrepresented sequences, we applied a step-wise reductionist analysis through (1) determination of the degree of linkage disequilibrium (LD) between purportedly associated alleles, (2) haplotype frequencies comparisons, and (3) primary sequence comparisons of disease-associated versus non-disease-associated alleles to identify crucial differences in amino acid residues in putative peptide binding pockets. Collectively, our data provide extended support for the hypothesis that the HLA associations in Caucasian PV patients map to DRB1*0402 and DQB1*0503 alone. Further structure-function studies will be required to define the exact mechanisms of HLA-mediated control of susceptibility and resistance to disease.     

Novel Mutations in TACI (TNFRSF13B) Causing Common Variable Immunodeficiency

Introduction

Common variable immunodeficiency (CVID) is a heterogeneous syndrome characterized by impaired immunoglobulin production. The disorder is also characterized by co-occurrence of autoimmune, lymphoproliferative, and granulomatous diseases. Mutations in the gene encoding TACI (Transmembrane Activator and CAML Interactor, TNFRSF13B) were previously found to be associated with CVID.

Materials and Methods

We therefore sequenced TNFRSF13B gene in a cohort of 48 Iranian CVID patients. Expression of TACI and binding of A proliferation-inducing ligand (APRIL) were tested by FACS.

Results

We identified one patient with a homozygous G to T substitution in the TNFRSF13B gene at the splice site of intron 1 (c.61+1G>T), which abolished expression of the TACI molecule and binding capacity of APRIL. This represents the second CVID patient in the world with a complete absence of TACI expression. B cell lines from family members carrying the same mutation in a heterozygous form showed a reduced level of TACI expression and APRIL-binding capacity, suggesting a gene dosage effect. In addition, we found the previously recognized C104R and C172Y mutations in a heterozygous form in two patients with CVID and one, novel, heterozygous P42T mutation.

Conclusion

TACI mutations were observed in Iran CVID patients in a similar frequency as in other Caucasian populations. The novel mutations identified in this study support the notion of a crucial role for TACI in B cell differentiation.     

HLA-Cw*1701 is associated with two sub-Saharan African-derived HLA haplotypes: HLA-B*4201, DRB1*03 and HLA-B*4202 without DRB1*03

Different extended haplotypes have been described for many ethnic groups, such as African-Americans. The complotype FC(1,90)0 is in linkage disequilibrium with HLA-B42, DRB1*0302 in African-Americans and Southern African Xhosa individuals, suggesting a common ancestry. In order to analyze the distribution of Cw*17 alleles (Cw*1701, 1702) in relation to this African-derived extended haplotype, we studied a large panel of samples from African-American individuals and additionally a group of selected samples carrying HLA-B42, DR3 and HLA-B42, non-DR3 antigens. HLA alleles were assigned using sequence-specific amplification (SSP) and sequence-specific oligonucleotide probe hybridization (SSOP). We have found that all haplotypes (10 in total) carrying the extended haplotypes [HLA-B42, FC(1,90)0, DRB1*0302] were positive for HLA-Cw*1701. Interestingly, HLA B*4201 was found in all samples (17 in total) carrying HLA-B42, DR3, Cw*1701, whereas HLA-B*4202 was found in 10 out of 13 samples from individuals carrying HLA B42, Cw*1701 non-DR3. These findings suggest that HLA-Cw*17 polymorphism is conserved in different ethnic populations and that HLA-B42 alleles seem to separate at least different African-derived haplotypes. The historical context of these findings are important for the study of human evolution and they may be useful for the development of strategies in the search for possible donors in organ transplantation for African-derived populations.     

MHC class I chain-related gene B promoter polymorphisms and celiac disease

The possibility that susceptibility to celiac disease (CD) might be influenced by the MHC class I chain-related gene family, MICA and MICB, has been previously reported. In this study, we analyzed the MICB promoter and examined the association of the polymorphisms found within such in a group of CD patients. To study the MICB promoter we sequenced the 5' flanking region of MICB gene in DNA from homozygous B-lymphoblastoid cell lines corresponding to the most frequent MICB alleles found in our population (MICB*00502, MICB*002, MICB*004, and MICB*008). DNA from a MICB*003 homozygous individual was also analyzed. Sequence analysis revealed six single nucleotide polymorphisms located at positions 45860 C/A, 45862 G/C, 45877 C/G, 46113 A/C, 46219 G/C, and 46286 G/C and an insertion of 2 bp --/AG at position 45944 according to the published genomic sequence. Those polymorphisms were found to be associated in four different haplotypes corresponding to different MICB alleles. Subsequently, 126 CD subjects and 117 healthy controls were typed by polymerase chain reaction using sequence-specific primers for these polymorphisms. MICB promoter polymorphism haplotypes were also found in our population and showed strong linkage disequilibrium with MICB alleles. MICB promoter polymorphism Haplotype 3, included in MICB*002 and MICB*008 alleles, was found to be overrepresented in CD patients (79.4% CD patients vs 45.3% healthy controls; p(c) < 0.0001; OR = 4.64; CI 95% = 2.64-8.16). Both MICB*008 and MICB*002 alleles were found as part of the CD susceptibility extended haplotypes B8/DR3/DQ2, B18/DR3/DQ2, and DR4/DQ8.     

The Role of HLA DQ2 and DQ8 in Dissecting Celiac-Like Disease in Common Variable Immunodeficiency

Objectives

Gastrointestinal manifestations are frequent in patients with common variable immunodeficiency (CVID), and some of the patients present with celiac-like features. Diagnosing celiac disease (CD) in CVID however is challenging, as autoantibody detection and histopathology of the small intestine cannot reliably discriminate between classic CD and a celiac-like disease in these individuals. For the development of classic gluten-sensitive CD a certain HLA haplotype involving the loci DQA1* and DQB1* and encoding two different HLA DQ heterodimers is the prerequisite. We aimed to determine the frequency of these haplotypes in CVID patients with suspected CD. Furthermore, we report on autoimmune manifestations and the lymphocyte phenotype in these patients.

Methods

By retrospective analysis data on gastrointestinal symptoms, diet, concurrent autoimmune diseases, and routine laboratory values were collected. CVID patients were classified according to their B-cell phenotype. Expression of HLA-DQA1* and HLA-DQB1* alleles were determined by genetic analysis.

Results

Twenty out of 250 CVID patients presented with a clinical phenotype resembling celiac disease. Four (20 %) out of these CVID patients carried the CD-associated HLA DQ2.5 or DQ8 heterodimer, while HLA DQ2.5 was present in 100 % of a CD control cohort. Gluten-free diet (GFD) resulted in a clinical and histological response in two out of four patients with HLA high-risk alleles for CD. The response could not be assessed in the remaining two patients, as these patients did not adhere sufficiently long to GFD. The percentage of autoimmune manifestations other than CD was high (50 %) in CVID patients presenting with a CD-like enteropathy, and most of these patients had an expansion of B-cells with low expression of CD21 (CD21low B-cells).

Conclusions

In CVID patients with suspected celiac disease typing of the HLA loci DQA1 and DQB1 can help to identify those that have a genetic susceptibility for CD. In CVID patients with a celiac-like phenotype but negative for CD-associated HLA-DQ markers, an autoimmune enteropathy (AIE) as part of an extended autoimmune dysregulation needs to be considered. This has important implications for further diagnostics and therapy of these patients.     

Does a central MHC gene in linkage disequilibrium with HLA-DRB1*0401 affect susceptibility to type 1 diabetes?

Subtypes of HLA-DR4 are associated with susceptibility or protection against type 1 diabetes (T1DM). We addressed whether this reflects linkage disequilibrium with the true susceptibility locus by studying broader MHC haplotypes marked by alleles of HLA-B, IKBL (adjacent to TNFA) and complement C4. The study used a largely Caucasian cohort from Western Australia. HLA-DRB1*0401 and HLA-DRB1*0405 marked susceptibility to T1DM. In Caucasians, DRB1*0401 occurs predominantly in the 44.1 ancestral haplotype (AH; HLA-A2,B44, DRB1*0401,DQB1*0301) and the 62.1AH (HLA-A2,B15(62),DRB1*0401,DQB1*0302). HLA-B15 marked susceptibility and HLA-B44 marked with resistance to T1DM in patients and controls preselected for HLA-DRB1*0401. A gene between TNFA and HLA-B on the 8.1AH (HLA-A1,B8,;DR3,DQ2) modifies the effects of the class II alleles. Here, alleles characteristic of the 62.1AH (C4B3, IKBL+446*T and HLA-A2,B15) were screened in donors preselected for HLA-DRB1*0401. C4B3 was associated with diabetes, consistent with a diabetes gene telomeric of MHC class II. However, increases in carriage of IKBL+446*T and HLA-A2,B15 were marginal, as too few control subjects were available with the diabetogenic alleles. However, with these tools, selection of HLA-DRB1*0401, DQB1*0302 donors who are positive and negative for C4B3 will allow bidirectional mapping of diabetes genes in the central MHC.