An HLA-D region restriction fragment length polymorphism associated with celiac disease

Refractory celiac disease: from bench to bedside

Refractory celiac disease is defined by the persistence of symptoms of malnutrition and intestinal villous atrophy for more than 6-12 months despite strict gluten-free diet in celiac patients. Diagnosis of this rare condition is made after excluding other causes of chronic small intestinal inflammation and villous atrophy and inadvertent intake of gluten. Over the past 15 years, multidisciplinary approaches have been developed to assess the mechanism of resistance to the diet, and two distinct entities have been delineated. Type II refractory celiac disease (RCD) can be defined as a low-grade intraepithelial lymphoma. RCD II is characterised by a massive accumulation of abnormal IEL that display an aberrant hybrid NK/T cell phenotype, contain clonal T cell rearrangement(s) and can mediate a cytolytic attack of the gut epithelium. This condition has a severe prognosis, largely due to the frequent transformation of RCDII IEL into overt aggressive enteropathy-type-associated T cell lymphoma. In contrast, in type I RCD, intestinal lymphocytes have a normal phenotype, and this generally milder condition remains often difficult to differentiate from uncomplicated CD except for the resistance to gluten-free diet (GFD). Several mechanisms may underlie resistance to gluten. Herein, we review the distinctive characteristics of RCD I and RCD II, the mechanisms underlying the onset of resistance to GFD, the risk of developing high grade lymphoma and possible clues to improve their treatment.

Celiac disease: from oral tolerance to intestinal inflammation, autoimmunity and lymphomagenesis

Celiac disease is a multifactorial disorder and provides a privileged model to decipher how the interplay between environmental and genetic factors can alter mucosal tolerance to a food antigen, lead to chronic intestinal inflammation, and ultimately promote T-cell lymphomagenesis. Here we summarize how HLA-DQ2/8 molecules, the main genetic risk factor for this disease can orchestrate a CD4(+) T-cell adaptive immune response against gluten, and discuss recent data which shed light on the innate and adaptive immune stimuli that collaborate to induce a proinflammatory TH1 response, a massive expansion of intraepithelial lymphocytes, and a cytolytic attack of the epithelium. The intestinal immune response driven in genetically predisposed patients by chronic exposure to gluten emerges as the pathological counterpart of normal acute intestinal responses to intracellular pathogens.

Celiac disease: diagnosis, autoimmune mechanisms and treatment

Celiac disease is a systemic autoimmune disorder triggered by the ingestion of gluten found in wheat and related grains. Once considered rare, celiac disease is now thought to affect more than one in 100 individuals, and is commonly associated with other autoimmune disorders. It predisposes patients to an increased risk of malignancy if left untreated. Celiac disease is HLA restricted as only HLA-DQ2 and -DQ8 are able to bind deamidated gluten with sufficient affinity to trigger an immune response. Both cellular and humoral immune activation occur, leading to local tissue damage and antibody formation. These antibodies, primarily to tissue transglutaminase, are the basis for highly accurate serologic testing, although the gold standard for celiac disease diagnosis remains small intestinal biopsy. Currently, the only treatment for celiac disease is a life-long gluten-free diet, although multiple novel therapeutic modalities are being studied. Although most individuals with celiac disease respond completely to gluten withdrawal, 10-20% have persistent symptoms at some point during their course and less than 1% develop refractory celiac disease, an entity of substantial morbidity.

Recent advances in the understanding of celiac disease: therapeutic implications for the management of pediatric patients

Celiac disease (CD) is an autoimmune condition occurring in genetically susceptible individuals characterized by inflammatory injury to the mucosa of the small intestine after the ingestion of wheat glutens or related barley and rye products. Originally thought to be highly prevalent only in Northern European populations, growing evidence indicates a much higher prevalence in many other regions, including the US as well as South America, North Africa, and Asia. The growing awareness that pediatric patients may present with quite diverse and protean manifestations and the significant impact of CD on childhood development has prompted efforts to increase CD awareness for the early diagnosis and treatment of this disease. The current diagnostic criteria for CD requires characteristic histologic findings in small bowel biopsies and clinical remission when placed on a gluten-free diet. Serologic testing for CD can provide additional support for the diagnosis of CD or a means to assess efficacy and adherence to a gluten-free diet. The mainstay of treatment remains the institution of a gluten-free diet. However, patients with refractory CD may require treatment with immunosuppressant medications. With the increased identification of specific gluten epitopes and understanding of the pathogenesis of CD, future therapies may rely on genetically altering gluten proteins, immunization techniques, or therapies focused on either the development of specific immune tolerance or regulation of mucosal inflammation.

Pathological and clinical significance of increased intraepithelial lymphocytes (IELs) in small bowel mucosa

Intestinal intraepithelial lymphocytes (IELs) belong to a unique T-cell population interspersed between epithelial cells of both the small and large intestine. It is becoming increasingly recognised that an increased number of IELs with a normal villous architecture is within the wide spectrum of histological abnormalities observed in coeliac disease. An increased number of IELs is the earliest pathological change following gluten challenge and a high IEL count may be the only sign of gluten sensitivity. Therefore, the finding of a raised IEL count with normal villous architecture is of sufficient clinical importance to be reported in routine small bowel biopsies. However, it is evident that not all small intestinal biopsy specimens showing increased IELs are explained by gluten sensitivity. Increased IELs in small bowel mucosa have also been associated with autoimmune disorders, tropical sprue, food protein intolerance, Helicobacter pylori-associated gastritis, peptic duodenitis, parasitic and viral infections, as well as the development of intestinal lymphoma. Histological examination of a biopsy specimen of the small bowel remains the diagnostic gold standard for coeliac disease. There will be an ever increasing demand for histological confirmation of gluten sensitivity in patients in whom the classic microscopic appearance of flattened villi may not have fully developed. The more widespread recognition by histopathologists of the pattern of injury manifested by increased numbers of IELs in intestinal biopsy specimens will certainly help in early diagnosis of coeliac disease, lessen diagnostic confusion and influence the modern practice of gastrointestinal tract medicine. This review discusses some of the recent developments in clinical pathology pertaining to increased IELs in small bowel mucosal biopsies.

Celiac sprue presenting as advanced liver disease

This case report describes the complexity of diagnosing celiac sprue in a patient who presented with features predominantly resembling that of advanced liver disease in the absence of diarrhea.

Coeliac disease in South Asians resident in Britain: comparison with white Caucasian coeliac patients

BACKGROUND

The catchment population of our hospital is ethnically diverse and we have seen a number of patients of South Asian origin with coeliac disease. We have suspected that there are differences compared with white Caucasian coeliacs, especially with respect to iron-deficiency anaemia and vitamin D deficiency at presentation.

AIMS

To compare the clinical and laboratory features of South Asian adult coeliac patients with adult white Caucasian coeliacs.

METHODS

We reviewed the notes of patients attending the adult coeliac clinic over the past 10 years. All patients were older than 16 years at diagnosis. There were 40 South Asians and 90 white Caucasians. Symptoms, haematology, biochemistry, endomysial antibody status, HLA alleles and small bowel histology at presentation were compared between the two racial groups.

RESULTS

There were significant differences between the racial groups. South Asians were younger at presentation than the Caucasian patients (mean age 27 years compared with 47 years respectively, P<0.0001); they were less likely to have 'irritable bowel syndrome' symptoms (P<0.01), but more likely to have features of vitamin D deficiency (P<0.03). Their haemoglobin (P<0.05), mean cell volume (P<0.0004), serum iron (P<0.01), transferrin saturation (P<0.05), serum 1,25-dihydroxyvitamin D3 (P<0.002), and levels were lower, while serum alkaline phosphatase levels were higher (P<0.04) than in white Caucasian coeliac patients. There were no differences with respect to serum folate, vitamin B12, serum calcium, alanine aminotransferase and small bowel histology. IgA class endomysial antibody positivity was similar in the two groups (88.5% for South Asians compared with 73.5% for white Caucasians). White Caucasian patients were significantly more likely to be DQ2-positive than the South Asian patients (97.2% compared with 83.3%, P=0.02).

CONCLUSION

South Asians with coeliac disease are less likely to present with 'irritable bowel syndrome' symptoms, but more likely to have features of vitamin D deficiency and iron deficiency, and have a higher alkaline phosphatase than white Caucasians. The differences in HLA alleles seen in South Asians with coeliac disease compared with white Caucasian patients suggests that among the South Asians, non-HLA regions may play a stronger role in disease susceptibility and presentation.

Endocrine autoantibodies

The autoantibody assays that exist and that are being refined are of increasing importance to a broad spectrum of endocrine disorders. This is particularly true for type IA diabetes, which is one of the best-studied organ-specific autoimmune diseases. Autoantibodies are used as valuable markers in prediction and prevention studies of type IA diabetes. Autoantibodies related to other endocrine organs are also important because multiple related autoimmune endocrine and non-endocrine disorders are increased in frequency in patients and their families with autoimmunity. The availability of highly sensitive and specific autoantibody assays for the various endocrine disorders can allow physicians to better diagnose and promptly treat these conditions.

Pathomechanisms in Celiac Disease

Celiac disease is a complex autoimmune disease which is characterized by a strong genetic association (HLA-DQ2 or -DQ8), gluten as nutritional etiological factor, and the enzyme tissue transglutaminase as endomysial autoantigen. Patients develop highly predictive IgA autoantibodies to tTG. Certain gluten peptides are presented by the disease-associated HLA-DQ2/DQ8 molecules leading to stimulation of gluten-specific T cells. This immune response which is driven in the lamina propria causes the mucosal transformation characteristic for celiac disease. Increased intestinal expression of tTG in patients with CD appears to play an important role in the pathogenesis of CD. Thus, modification of gluten peptides by tTG, especially deamidation of certain glutamine residues, can enhance their binding to HLA-DQ2 or -DQ8 and potentiate T cell stimulation. Furthermore, tTG-catalyzed cross-linking and consequent haptenization of gluten with extracellular matrix proteins allows for storage and extended availability of gluten in the mucosa. New therapeutic approaches aim at proteolytic destruction of immunodominant gliadin peptides that are resistant to intestinal enzymes by bacterial prolyl endopeptidases, the inhibition of tTG activity with highly specific enzyme inhibitors or at HLA-DQ2/DQ8 blocking peptide analogues.

Ganglioside reactive antibodies in the neuropathy associated with celiac disease

We tested patients with celiac disease (CD) for the presence of serum anti-ganglioside antibodies. Six of twenty-seven patient sera were reactive against brain gangliosides by an agglutination immunoassay. Neurological examination in all six revealed the presence of distal sensory loss, consistent with the diagnosis of peripheral neuropathy. When tested by ELISA for antibodies to isolated GM1, GM2, GD1a, GD1b, GT1b, and GQ1b gangliosides, all six were positive for IgG antibodies to at least one. The neuropathy of celiac disease may be autoimmune and associated with anti-ganglioside antibodies. The presence of IgG reactivity furthermore implicates a T cell-mediated response to ganglioside antigens.

Current concepts of celiac disease pathogenesis

Our knowledge of celiac disease pathogenesis has recently made rapid progress. The disorder is now considered the result of a complex interplay of intrinsic (genetic) and variable extrinsic (environmental) factors that explain the wide spectrum of clinical manifestations ranging from asymptomatic to severe malabsorption. Gluten peptides are efficiently presented by celiac disease-specific HLA-DQ2- and HLA-DQ8-positive antigen-presenting cells, and thus drive the immune response, predominantly in the connective tissue of the lamina propria. Tissue transglutaminase, which has been identified as the highly specific endomysial autoantigen, is released from cells during inflammation. It may potentiate antigen presentation by HLA-DQ2 and HLA-DQ8 by deamidating or cross-linking gluten peptides. The result is lamina propria T-cell activation and mucosal transformation by activated intestinal fibroblasts. In the future, manipulation of the gut-associated lymphoid tissue may allow reduced sensitivity or even generate oral tolerance to gluten. Long-standing untreated celiac disease, even if clinically silent, predisposes for other autoimmune diseases. Therefore, population screening for immunoglobulin A antibodies to tissue transglutaminase seems justified.

RFLP characterization of the upstream regulatory region of the HLA-DQA1 gene

We have performed population and family studies of the distribution of DNA restriction length polymorphisms (RFLPs) in the 5' region of the HLA-DQA1 gene using a probe which corresponds to a sequence of the 5' flanking region of HLA-DQA1. Southern analysis detected four polymorphic fragments (X1, X2, X3 and X4) with XbaI and three fragments (E1, E2 and E3) with EcoRI. Family segregation studies showed that these RFLPs segregated in cis with the parental HLA haplotypes. Analysis of haplotypic associations of the X and E polymorphisms with each other and with HLA-DQA1 alleles demonstrates that DQA1 alleles can be further subtyped according to the particular XE combination which they carry. Hence, definition of these alleles provides new markers for HLA haplotyping and allows further splitting of otherwise identical DQA1 alleles. This information may be helpful for studies of association of disease susceptibility and autoimmunity with HLA haplotypes.

HLA susceptibility genes in celiac disease: genetic mapping and role in pathogenesis

The overrepresentation of particular HLA alleles in patients with celiac disease was first noted two decades ago. Several lines of evidence obtained during the last years strongly suggest that a particular HLA-DQ heterodimer, encoded by the DQA1*0501 and DQB1*0201 genes in cis or trans configuration, confers the primary disease susceptibility. This paper reviews the evidence behind this concept and discusses how this particular DQ molecule may be involved in the pathogenesis.

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.

Immunoglobulin and HLA-DP genes contribute to the susceptibility to juvenile dermatitis herpetiformis

HLA-DQ genes and gluten diet are the main factors involved in the pathogenesis of Dermatitis Herpetiformis (DH), as well as Coeliac Disease (CD). However other genetic factors are probably relevant, since about 10% of the patients with DH and CD lack the DQA1*0501/B1*0201 heterodimer while the majority of individuals presenting this genotype and also being exposed to gluten diets did not suffer from these diseases. To evaluate the role of other genes, 36 Northern Italian children with DH were analysed for DNA polymorphisms at HLA-DP and immunoglobulin (Ig) heavy chain loci. DPA1*0201 and DPB1*1301 frequencies were higher in patients than in controls (Pc = 0.0357 and Pc = 0.0273). With respect to immunoglobulin heavy chain restriction fragment length polymorphisms (RFLP), the 4.6 kb SacI RFLP at the switch alpha 2 gene was more frequent in patients (0.13) than in controls (0.019; Pc = 0.036). Moreover, rare alleles or duplications in the switch regions occurred more frequently in the patients than in the controls. These results support the hypothesis of a multifactorial inheritance of DH, the HLA and Ig constant heavy chain genes being some of the loci contributing to the susceptibility. In accordance with previous CD studies, these data also confirm that DP subregion is probably involved in the pathogenesis of DH.

A tyrosine sulfated human glycoprotein with an unusual cell distribution

We describe a human integral cell surface glycoprotein (Mr 142 kD), recognized by monoclonal antibody M2B3. This glycoprotein is absent from resting peripheral blood lymphocytes, but becomes expressed in significant levels with mitogen activation. The M2B3 glycoprotein is present on epithelial cells in the basal layer of epidermal and esophageal tissue as well as in several fresh tumors examined. In addition, it is present on smooth muscle tissue throughout the gastrointestinal tract, but is absent from smooth muscle from several other tissue sources, skeletal muscle and cardiac muscle. The M2B3 glycoprotein is similar, but not identical, in apparent Mr to a transformation-associated glycoprotein, Q14. Further, the M2B3 and Q14 species are related antigenically. Nonetheless, M2B3 and Q14 are distinct glycoproteins based on clear differences in cell distribution and in partial peptide mapping. The M2B3 antigen described herein is sulfated on tyrosine, and represents one of the few cell surface proteins described to date that is sulfated on tyrosine residues. Our studies suggest the function of the M2B3 glycoprotein is likely to be associated with cell proliferation of cell adhesion.

Association between a T cell receptor restriction fragment length polymorphism and systemic lupus erythematosus

The present study was designed to test the possibility that T cell receptor genes are associated/linked to those involved in systemic lupus erythematosus (SLE). Genomic DNA was isolated from 31 unrelated Caucasian SLE patients, 34 unrelated Caucasian normals, 5 multiplex American Caucasian SLE families, 9 multiplex Mexican SLE families, and 13 unrelated Mexican normals. The DNA was digested with Pst I, electrophoresed, and transferred to membranes by the Southern blot method. The blots were probed with a cDNA probe for the alpha chain of the T cell receptor. 13 polymorphic RFLP patterns were recognized. 1.3- and 3.0-kb band pairs were observed in 15 of 31 of American Caucasian patients and 4 of 34 American Caucasian controls (chi square, 8.81; P less than 0.002; relative risk, 7); there was no association of any RFLP pattern with Mexican SLE. The cDNA probe was cut with Rsa I, EcoR I, and Ava II into fragments corresponding to the V, J, C, and 3'UT regions. Only the fragment corresponding to the constant region reacted with the 1.3/3.0-kb band pair. These observations suggest that a genetic marker of the constant region of the alpha chain of the T cell receptor is associated with genes involved in SLE.

An HLA class II region restriction fragment length polymorphism (RFLP) in patients with dermatitis herpetiformis: association with HLA-DP phenotype

Dermatitis herpetiformis (DH) is characterized in part by an associated gluten-sensitive enteropathy (GSE), and a strong association with the HLA antigens HLA-A1, -B8, -DR3, and -DQw2, essentially identical to that seen in patients with isolated GSE (celiac disease). A 4.0-kb RsaI RFLP has been identified using a DQ beta-chain cDNA and localized to the HLA-DP beta-chain region. This RFLP has been found more frequently in patients with isolated GSE than in normal HLA matched controls. We have analyzed genomic DNA from 24 patients with DH and 15 HLA-matched controls to determine if this 4.0-kb RsaI RFLP was present in patients with DH. Twenty-one of 24 (87%) of patients with DH were found to have this RFLP as compared to 7 of 10 (70%) HLA-DR3, -DQw2 matched control subjects (p = 0.23). Thus, the 4.0-kb RsaI RFLP detected in patients with isolated GSE is also present in patients with DH; however, its frequency in DH patients does not differ significantly from that of HLA matched controls. Family studies of patients with DH revealed that although the 4.0-kb RsaI RFLP segregated with the HLA-A1, -B8, -DR3, -DQw2 haplotype in one family, it did not segregate with this disease-associated haplotype in two other families. In both patient and control populations, this RFLP was associated with HLA-DPw1 or -DPw3 phenotypes; 25 of 26 (96%) HLA-DPw1 or -DPw3 subjects were found to have this RFLP compared to only 1 of 6 (17%) who did not express HLA-DPw1 or -DPw3 (pc = 0.0009). These population and family data suggest that this 4.0-kb RsaI RFLP is primarily associated with the HLA-DPw1, -DPw3 phenotype, rather than the clinical manifestations of DH. These data further document that the strongest association of DH with HLA antigens remains with HLA-DQw2 and HLA-DR3 antigens.

Increased incidence of certain TCR and HLA genes associated with myasthenia gravis in Italians

In order to study the immunogenetics of myasthenia gravis (MG), we analysed the TCR and HLA-class II genes from Italian and Californian myasthenic patients. We investigated polymorphisms of the TCR using the full length cDNA probes pGA5 and the pT10 for the alpha and beta chains, respectively. The 6.3 kb and 2.0 kb polymorphic markers, revealed by the PssI enzyme and the alpha chain probe, were shown to be significantly associated with MG. Italian MG patients were HLA typed, and allele frequencies showed a significant association of DR3 and DQw2 with MG. The relative risk calculated for DR3 was 7.4. T-cell proliferative responses to peptides of the AchR alpha chain were also studied and no associations with TCR RFLP analysis or HLA-class II typing were observed.

HLA-DP and coeliac disease: family and population studies

We investigated polymorphism of HLA-DP genes in three DR3 related diseases, confirming an association of coeliac disease with a Bgl II DP alpha polymorphism (a restriction fragment sized 3.5 kb present in 75% of patients compared to 34% of control subjects, p less than 0.001), and finding a weaker association with dermatitis herpetiformis (57% v 34%, p = 0.01) and no association with insulin dependent diabetes mellitus. The association with coeliac disease was further investigated. Msp I DP beta polymorphism was studied in 52 healthy subjects and 59 patients: a 4.9 kb fragment was present in 51% of patients with coeliac disease compared to 11.5% of control subjects (p less than 0.001). Furthermore, nearly all subjects with the DP alpha 3.5 kb fragment also had the DP beta 4.9 kb fragment. However, disease frequency was still increased in the DP alpha 3.5 positive/DP beta 4.9 negative group. In seven families, each with at least two affected members, while the DP alpha 3.5 fragment was frequently present in patients it did not preferentially segregate with any particular HLA haplotype--for example, those associated with DR3 or DR7--and therefore is not part of an extended haplotype associated with coeliac disease. We therefore conclude that a gene(s) in the HLA-DP region predisposes to coeliac disease independently of the HLA-DR/DQ regions.

Cellular hypersensitivity to a synthetic dodecapeptide derived from human adenovirus 12 which resembles a sequence of A-gliadin in patients with coeliac disease

The human intestinal adenovirus serotype 12 (Ad12) may be implicated in the pathogenesis of coeliac disease by virtue of immunological cross reactivity between epitopes shared by its early region E1b protein and A-gliadin. In the present study a synthetic dodecapeptide from the corresponding viral epitope (Ad12E1b, residues 384-395) was tested for its effect on peripheral blood mononuclear cells from 22 treated and eight untreated patients with coeliac disease, 22 healthy subjects, 11 patients with ulcerative colitis, and 11 patients with Crohn's disease by an indirect leucocyte migration inhibition assay. In addition, the effect of both the viral and the gliadin synthetic peptides was studied by proliferation and migration assays simultaneously performed in an unselected subgroup of 12 treated coeliac patients and 12 healthy subjects of the study. Coeliac patients with untreated disease showed no response to the viral peptide compared with treated patients (p greater than 0.1). Treated coeliac patients showed a significantly different response from healthy control subjects and control patients with disease (p less than 0.001) which was dependent on the concentration of the viral peptide. In the subgroup of the treated coeliac patients (n = 12) there was a significant correlation between the responses in the migration and the proliferation assay using either the viral (p less than 0.02) or the gliadin (p less than 0.005) peptide at the highest concentration (33.3 micrograms/ml). Furthermore, the responses obtained using viral peptide correlated significantly with the responses obtained with gliadin peptide in both the migration (p less than 0.001) and the proliferation (p less than 0.001) assays. These results show that in coeliac patients there is pronounced cross reactivity at the level of T cell recognition between synthetic peptides derived from the Ad12 and A-gliadin. This antigenic cross reactivity may be involved in the pathogenesis of coeliac disease.

HLA in juvenile dermatitis herpetiformis: clinical heterogeneity correlated with DNA and serological polymorphism

A group of 30 Italian children affected by Dermatitis Herpetiformis (DH) was analysed for HLA region polymorphisms with both serological and DNA methods. Serological typing was performed on HLA-A, B, C, DR, DQ antigens and C4A, C4B, Bf polymorphisms. DNA RFLPs obtained with TaqI enzyme were investigated with cDNA probes specific for DR beta, DQ alpha and DQ beta genes. The results were correlated with intestinal involvement and age at onset of the disease. The following observations were made: (1) the intestinal biopsies revealed a direct correlation between degree of lesions and age at onset of DH; (2) a significantly increased relative risk (RR) was found for the following HLA antigens: A1 (RR = 2.2), B8 (RR = 6.2), Cw7 (RR = 3.9), C4AQ0 (RR = 7.4), DR3 (RR = 5.2), DR7 (RR = 4.4), DRw53 (RR = 4.7), DQw2 (RR = 6.0); (3) B8 and DR3 were significantly more frequent in patients with severe intestinal lesions; and (4) of the two DR3 subtypes revealed by RFLP typing, only 3.1 showed an increased frequency in DH patients (RR = 8.4). It is suggested that the susceptibility to Juvenile DH is determined by the same genes, within the HLA region, that are associated with Coeliac Disease.

Molecular basis of human leukocyte antigen class II disease associations

This chapter focuses strictly on the HLA MHC class II genes and molecules with regard to how they contribute to better delineation of the genetic associations and how the current knowledge of their structure, expression, and functions can be used to speculate on their role in the pathogenesis of disease. Because of the strong linkage disequilibrium between loci and alleles, the chapter restricts the description of the genetic associations to only the most recent data, mainly generated by molecular means, and because they supercede in precision and accuracy the previous data obtained by serological methods. Because the HLA system displays the unusual feature of strong linkage disequilibrium between loci and alleles, the genetic traits found to be associated with disease do not emerge at random. The pattern of genetic associations follow an almost constant trend. The associations gain strength each time an additional locus centromeric to the precedent is individualized. The advances made in this respect almost parallel the introduction of progressively more refined typing procedures, which allow the division of former genetic entities (loci and alleles) into additional subtypes. Among the HLA-associated diseases, or at least for those diseases in which an autoimmune process is suspected to be directly relevant to the pathogenesis, the associations are with genes and molecules of the HLA-D region (HLA class II genes and products). The most recent data assigns the disease susceptibility to common amino acid sequences present on an HLA class II molecule within its “active” site.

Restriction fragment length polymorphism in HLA class II genes of Latin-American Caucasian celiac disease patients

In the present study Latin-American celiac disease patients were analyzed for the frequency of certain HLA class II restriction fragment length polymorphisms in order to investigate whether they exhibited the normal associated alleles or showed unusual class II variants. A DPB/RsaI 4.0-kb fragment that was shown to be significantly increased among North Americans celiac disease patients of the DR3,DQw2 haplotype was found with similar frequency in Latin-American control and celiac disease individuals. A DPA/BglII 3.7-kb fragment previously shown to be increased among British celiac disease patients was also present with similar frequency among Latin-American control and celiac disease individuals. These results show that the frequency of the HLA-DP region-derived restriction fragment length polymorphisms linked to celiac disease differs between Caucasian populations of different ethnic backgrounds (Anglo-Saxon and Latin-American). On the other hand, DNA samples from 13 patients and 14 controls bearing the DR5/DR7 phenotype (which is significantly associated with celiac disease in Latin populations) were investigated for the presence of particular restriction fragment length polymorphisms disproportionally present in celiac disease individuals. No significant differences were found between controls and patients when the DNA was analyzed with 10 different restriction enzymes and probes for DRB, DQA, DQB, and DPB HLA class II sequences.

Lack of informative HLA restriction fragment length polymorphisms in autoimmune chronic active hepatitis

Autoimmune chronic active hepatitis (CAH) is strongly associated with HLA-B8, DR3. Accordingly, DNA was isolated from 10 HLA-B8, DR3 control subjects and 11 patients with autoimmune CAH and analyzed for informative restriction fragment length polymorphisms using HLA-DQ beta and DR beta probes, and six enzymes, Hinc II, Bgl II, Bam HI, Rsa I, Taq I and Msp I. None of the polymorphic fragments demonstrable was discriminatory for autoimmune CAH. A genetic polymorphism in the HLA-B8, DR3 region predisposing to autoimmune CAH may not have been detecting owing to an insufficient number of probes or enzymes used, or alternatively HLA-DR3 is predisposing by an effect on immune regulation or suppression.

Alterations in HLA-DP and HLA-DQ antigen frequency in patients with dermatitis herpetiformis

Dermatitis herpetiformis (DH) is associated with a markedly increased frequency of the HLA class II antigens DR3 and DQw2. To investigate a possible role of HLA-DP (or closely associated genes) in the pathogenesis of DH as well as to confirm the previously described alterations of HLA-DR3 and HLA-DQw2 antigen frequency, we have typed 43 patients with DH for HLA-DP, HLA-DQ, and HLA-DR antigens. All patients with DH had typical clinical and histologic features, as well as granular deposits of IgA at the dermal-epidermal junction by direct immunofluorescence. HLA-DR3 was expressed in 41 of 43 (95%) DH patients, whereas HLA-DQw2 was expressed in all 43 (100%). The overall distribution of HLA-DP antigens in patients with DH was significantly different from that seen in all controls and in HLA-DR3 and HLA-DQw2 controls (p less than 0.02). Examination of the frequency of individual DP antigens revealed that HLA-DPw1 was increased (42% of patients with DH vs 11% of all controls and 26% of DR3 positive controls), but this increase was not statistically greater than that expected due to the disequilibrium linkage of DPw1 with DR3/DQw2. Patients with DH, however, did have a statistically significant decreased frequency of DPw2 (14% of patients vs 31% of all controls and 41% of DR3 positive controls) (pc less than 0.05). Studies of three informative families demonstrated that the DPw2 genes of the DH patients were not present on the haplotype thought to carry a DH susceptibility gene (HLA-A1, HLA-B8, HLA-DR3, HLA-DQw2). A role of HLA-DP region genes in the pathogenesis of DH is further suggested by the observation that HLA-DPw1 was expressed in 82% (9 of 11) of DH patients with IgA antibodies against dietary antigens as compared with only 33% (4 of 12) of patients without IgA antibodies. HLA-DP genes or genes closely linked to them may be important in DH either as markers of the disease haplotype or by direct involvement in its pathogenesis.

Analysis of RNA transcripts for HLA class II genes in human small intestinal biopsies

Studies of the expression of selected genes within the intestinal mucosa will provide important new information about physiologic pathological processes that effect mucosal growth, differentiation, and function. To study gene expression in the gut, we developed a method to obtain sufficient undegraded RNA from human endoscopic intestinal biopsy specimens for Northern and slot blot analysis. To verify the method, we examined the differential expression of HLA class II genes in small intestinal mucosa. Levels of RNA transcripts for HLA-DR, -DP, and -DQ alpha and beta chains were assessed in freshly isolated endoscopic intestinal mucosal biopsy specimens and compared with levels in Epstein-Barr virus transformed B cells from the same individuals. Sufficient undegraded cellular RNA with distinct 28S and 18S ribosomal bands could be obtained from as few as two 2-3 mm endoscopic biopsies. Using chain and locus specific cDNA probes, HLA-DR, -DP, and -DQ subregion genes were shown to be expressed in intestinal mucosa, with the relative magnitude of RNA transcripts being DR greater than DP greater than DQ. The same hierarchy of expression was seen for EBV-transformed B cell lines. This method, in conjunction with the polymerase chain reaction for amplifying specific RNA transcripts and in situ hybridisation methods for the cellular localisation of RNA transcripts, will enable studies on the regulation of gene expression in the intestinal mucosa.

Southern blot analysis of HLA-DP gene polymorphisms in Caucasoid rheumatoid arthritis (RA) patients and controls

Despite extensive analysis of the incidence of HLA-DR and HLA-DQ allele frequencies in defined autoimmune disease groups, there is very little information available on HLA-DP allele frequencies. This is largely because HLA-DP typing has until recently been restricted to primed lymphocyte typing (PLT). However, allelic polymorphism of the HLA-DP subregion can now be studied by Southern blot analysis or genotyping with DPA1 and DPB1 probes. By direct counting of allele-specific DNA fragments, we have analyzed the frequencies of five major DP genotypes (DPw1, DPw2, DPw3/6, DPw4, and DPw5), in a large number of Caucasoid rheumatoid arthritis (RA) patients (n = 74), and controls (n = 91). The predicted frequency of DP alleles in both patient and control groups was comparable to PLT-determined DP allele frequencies in normal Caucasoids. However, the gene frequency of DPw4 was increased in the RA patients, with 51% of the patients studied scoring as DPw4, 4 homozygotes. With the exception of one possible combination (DPw5 and DRw6) in the controls, no significant linkage disequilibrium was detected between DP and DR alleles in either patient or control groups. Thus the prevalence of DPw4 in the RA patients is independent of any disease association with the DR loci, and may represent a new class II association with RA.

Structural analysis of the HLA-DR, -DQ, and -DP alleles on the celiac disease-associated HLA-DR3 (DRw17) haplotype

Celiac disease is strongly associated with the HLA class II D-region serologic markers DR3 (DRw17) and DQw2. Moreover, by restriction fragment length polymorphism analysis, greater than 90% of DR3 (DRw17), DQw2 celiac disease patients have a polymorphic 4.0-kilobase Rsa I DP B gene DNA fragment. The present study sought to determine if there is a unique HLA class II D-region A or B gene structural variant on the DR3 (DRw17) haplotype found in celiac disease. The polymorphic second exons of the coding DRB, DQA and DQB, and DPA and DPB genes in celiac disease patients with the DR3 (DRw17) haplotype were sequenced after amplification by the polymerase chain reaction. To define the DP B genes associated with celiac disease, the second exons of the coding DP B genes from 27 celiac disease patients were amplified similarly and probed by using a panel of sequence specific oligonucleotides. The HLA-DR, -DQ, and -DP A and B gene second exon sequences of celiac disease patients were noted to be identical to sequences that can be found also, although at a significantly lower frequency, in unaffected individuals. This is compatible with a disease model wherein the HLA class II genes on the DR3 (DRw17) haplotype are necessary, but not sufficient, for the phenotypic expression of celiac disease. Analysis of the DP B genes revealed a significant increase in the frequency of the alleles DPB1 and DPB3 in celiac disease. Furthermore, the increased frequency of the 4.0-kilobase Rsa I DP B gene restriction fragment length polymorphism in celiac disease can be accounted for by the overrepresentation in disease of the alleles DPB1 and DPB3. The HLA-associated susceptibility to celiac disease appears to be multigenic, with specific, but structurally normal, allelic variants in the DP and DQ/DR subregions contributing to disease susceptibility.

Development and characterisation of T lymphocyte lines from human small intestinal biopsies

T lymphocyte lines were developed from human small intestinal biopsies obtained at the time of gastroduodenoscopy. Lines were established as outgrowths from biopsy specimens in microculture using a combination of T cell mitogens, indomethacin, interleukin (IL-2) and autologous irradiated feeder cells. The predominant phenotype of T cells after six to 12 weeks in culture was CD2, CD3, and CD4 positive. Functionally, these T cell lines secreted IL-2 in response to stimulation with phytohemagglutinin (PHA) and phorbol 12-myristate 13-acetate (PMA) in combination, but not to PHA or PMA alone. Two to 7% of cells in each line expressed natural killer (NK) cell-associated markers--that is, Leu 7, CD16, and Leu 19. Moreover, such cells were cytotoxic for NK sensitive targets, but not for NK resistant targets or allogeneic or autologous Epstein Barr Virus (EBV) transformed B cells. Sufficient numbers of small intestinal lymphoid cells for study were previously available only from patients undergoing surgical resections of the small bowel. The ability to isolate and culture human small intestinal T lymphocytes from gastroscopic intestinal biopsies provides an important new tool for studies of human small intestinal lymphocytes.

HLA class II DR, DQ, and DP restriction fragment length polymorphisms in rheumatoid arthritis

HLA class II restriction fragment length polymorphisms (RFLPs) were studied in 43 individuals with established seropositive rheumatoid arthritis (RA) and in a group of healthy controls. All patients and controls were tissue typed for HLA-A, B, and DR antigens. Rapid, initial screening for RA associated RFLPs was conducted by pooling DNA samples from 11 HLA-DR4 positive patients with RA and comparing the RFLP patterns with those seen in a pool of DNA samples drawn from 11 HLA-DR4 positive healthy controls. Candidate RA associated RFLPs were examined in our full panel of patients with RA and controls. In most cases the RFLPs detected showed no significant association with RA. An exception was a 13.0 kb DraI DQ beta associated RFLP, which, when HLA-DR4 positive patients with RA and controls were considered alone, showed a weak positive association with susceptibility to RA. This RFLP was not associated with known DR, DQ, or Dw specificities. These results show a distinct paucity of class II RA associated RFLPs but may indicate a role for DQ beta genetic variation in the aetiology of RA.

Major histocompatibility complex antigens in steroid-responsive nephrotic syndrome

An increased frequency of specific major histocompatibility complex (MHC) class I, II and III antigens in children with steroid-responsive nephrotic syndrome (SRNS) has been reported. This frequency distortion, in some cases, is thought to affect the outcome of the disorder. We studied the phenotypic frequency of HLA antigens -A, -B, and -DR, as well as complement proteins Bf and C4 in an unrelated population of 25 SRNS children. Complete MHC haplotypes were also derived for four families in which 8 individuals developed SRNS. HLA-DR8, with a relative risk of 4.8, showed the strongest association with SRNS. Nonetheless, the 95% confidence intervals of this and the relative risks for all other antigens fell below 1.0. No common haplotype was found in SRNS patients in whom complete family studies were available, and disease and inheritance of the MHC were discordant in two of these families. In this study of well-characterized SRNS patients we were unable to discover a clear association between this disorder and the MHC.

Immunopathogenesis of celiac disease

The immunopathogenesis of celiac disease requires interactions between genetic, environmental and immunologic factors. Genes within the class II region of the major histocompatibility complex (HLA-D region) represent a major component contributing to disease susceptibility. Structural studies of genes within the HLA-D region have shown that the class II HLA haplotype associated with celiac disease is extended, and includes not only the HLA-DR and DQ subregions, but also the HLA-DP subregion. The celiac disease-associated haplotype is marked in the HLA-DP subregion by a polymorphic 4 kilobase Rsa I genomic fragment derived from a DP beta chain. Other studies suggest that, in addition to dietary gliadins, a viral protein may play a role in the pathogenesis of celiac disease, perhaps by virtue of immunologic cross reactivity between antigenic determinant shared by the viral protein and alpha gliadins.

An HLA-DQ alpha allele identified at DNA and protein level is strongly associated with celiac disease

An HLA-DQ alpha cDNA probe showed upon hybridization a highly significant discrepancy between the RFLP of celiac disease patients and healthy controls. The 4.0-kb Bgl II restriction fragment was present in 97% of celiac disease patients (n = 30), compared to 56% in a healthy control population (n = 72) (RR = 14.9; p less than 0.0005). At the product level all celiac disease patients tested to date have one DQ alpha chain in common, designated HLA-DQ alpha 2.3, which is associated with the 4.0-kb Bgl II fragment. This HLA-DQ alpha allele identified at the DNA level and product level seems to be a better marker for genetic susceptibility to develop celiac disease than those available to date.

Studies on the interaction between alpha-gliadin and HLA and T cell receptor molecules in coeliac disease

Coeliac disease has a known strong linkage with the HLA complex and has also recently been linked to the T cell receptor genes but the mechanism whereby these genes confer susceptibility is not known. This study has examined two possible mechanisms: (i) direct, lectin-like binding of alpha-gliadin (the causative agent of CD) to HLA or TcR molecules and (ii) antigenic cross-reactivity between alpha-gliadin and HLA or TcR molecules. A flow cytometer was used to assess interactions between alpha-gliadin, anti-alpha-gliadin antibodies (raised in both coeliac patients and in rabbits) and EBV-transformed B cell lines from coeliac patients and HLA-matched and mismatched normal controls. The B cell lines were shown to express HLA-DP, -DQ and -DR antigens which are also found on coeliac intestinal epithelial cells. After incubating B cell lines with alpha-gliadin over a wide range of concentrations, no binding of alpha-gliadin to any of the cell lines could be detected with either of the gliadin-specific antibodies. This suggests that HLA molecules do not bind to alpha-gliadin in a lectin-like fashion. In contrast to the B cell lines, alpha-gliadin binding to peripheral blood monocytes could be demonstrated. This binding occurred equally to patient and control monocytes and was not influenced by HLA allotype. The second possibility tested was that alpha-gliadin and the disease-associated HLA molecule bear antigenic similarities. However, neither rabbit anti-gliadin serum nor purified human alpha-gliadin antibody bound directly to the B cell lines. Using peripheral blood T cells similar results were obtained; no binding of alpha-gliadin or antibodies to alpha-gliadin was found. Thus this study shows that the HLA and TcR associations with CD are not explained by the direct binding of alpha-gliadin to these molecules nor by a sharing of antigenic determinants between alpha-gliadin and these molecules.

Prevalence of coeliac disease in diabetic children and adolescents. A multicentre study

Screening for coeliac disease (CD) with serum antigliadin antibodies (AGA) was performed in 1032 diabetic children and adolescents. In 8 children CD had been diagnosed before study entry. Of the remaining 1024 children, 33 had an elevated AGA titre in the first serum sample. On follow-up an elevated AGA titre was confirmed in only 17 of 31 patients. Nine of the repeatedly positive patients underwent jejunal biopsy, and CD was diagnosed in two asymptomatic patients; both were positive for IgG- and IgA-AGA. Among 10 AGA-positive patients in whom biopsies could not be performed, only 1 showed IgA-AGA and thus carried a high risk for CD. From our results we estimate a prevalence of CD in Swiss and German diabetic children between 1.1% and 1.3%. False-positive AGA titres occurred significantly more often in patients with diabetes duration of less than 1 year. AGA testing reached a specificity of 99% if performed at least 1 year after the onset of diabetes. Children suffering from both diabetes and CD showed a diabetes manifestation at a significantly younger age than non-coeliac patients, whereas CD tended to be diagnosed at a remarkably late age.