Screening of coeliac disease in north Italian children with type 1 diabetes: limited usefulness of HLA-DQ typing

AIM

To determine the contribution of HLA-DQA1* and HLA-DQB1* genes to the risk of coeliac disease (CD) in a cohort of children with type 1 diabetes mellitus (T1DM) from northern Italy.

METHODS

Three hundred and fifty-seven children with T1DM, attending the Childhood Diabetes Unit of the University of Verona, have been regularly tested for serum IgA endomysial antibodies (EMA). All patients with positive EMA underwent small bowel biopsy to confirm the diagnosis of CD. HLA typing was performed in subjects with T1DM and CD, and in a control group of 79 EMA-negative patients with T1DM.

RESULTS

Of the 357 patients tested, 25 (7%) had CD. The frequency of HLA-DQA1*0501-DQB1*0201 (T1DM + CD 68% vs T1DM 62%) and of DQA1*0301-DQB1*0302 (T1DM + CD 40% vs T1DM 35%) haplotypes, between T1DM patients with and without CD, was statistically comparable. A trend towards a reduction of the risk of CD (p = 0.055, OR: 0.22, CI 0.05: 1.04) was observed in patients with T1DM (28% vs T1DM + CD 2%) who did not carry either the HLA-DQA1*0501-DQB1*0201 or the DQA1*0301-DQB1*0302 haplotype.

CONCLUSION

A high prevalence of HLA-DQA1* and -DQB1* susceptibility haplotypes for CD was observed both in EMA-negative diabetics and in those with associated CD. The implementation of screening programmes of CD in a T1DM population, based on the identification of HLA susceptibility haplotypes, seems to be of limited usefulness. Serial serologic screening of diabetic patients remains the advisable strategy.

[Latent celiac disease in subjects with serum anti-endomysial antibodies and normal intestinal biopsy]

OBJECTIVES

Data on the follow-up of a group of subjects with serum antiendomysial antibodies (EMA) and normal mucosal architecture at the intestinal biopsy are reported. Clinical problems concerning possible evolution of potential celiac disease (CD) towards gluten-induced histological damage are discussed.

METHODS

Eleven patients belonging to high-risk groups for CD (5 with type-1 diabetes, 2 with familiarity for CD and 4 with symptoms suggesting CD) who had a normal intestinal biopsy, despite positive antiendomysial test, were followed-up. Antigliadin and antitransglutaminase antibodies (anti-tTG) and HLA genotyping were also assessed. According to clinical and serological data a second biopsy was performed in six of them.

RESULTS

At the time of the first normal biopsy, all patients were positive for EMA and 5/8 for anti-tTG. Five of 6 subjects genotyped were HLA-DQ2+ or DQ8+. Six patients were rebiopsed after 1 to 4 years. Three had mucosal atrophy, 1 had mild increase of intraepithelial lymphocytes and 2 were morphologically normal.

CONCLUSIONS

Subjects with antiendomysial antibodies and normal intestinal biopsy deserve clinical and serological follow-up to reduce the time of possible latency of CD. Although good predictors of progression of the disease are not still available, antiendomysial antibodies assessment and HLA genotyping may help to suggest individuals at higher risk to develop gluten-induced enteropathy. This study confirms that subjects with persistent signs of gluten sensitivity and normal biopsy should be re-examined.

Analysis of CIITA encoding AIR-1 gene promoters in insulin-dependent diabetes mellitus and rheumatoid arthritis patients from the northeast of Italy: absence of sequence variability

Qualitative and/or quantitative alterations in the expression of the MHC class II molecules affect the onset and maintenance of the immune response and may be the basis of a wide variety of disease states, such as autoimmunity and immunodeficiency.CIITA is a major physiological regulator of the expression of MHC class II genes. The availability of CIITA ap- pears generally essential for MHC class II gene expression, and hence its own transcriptional regulatory mechanisms result of fundamental importance for a correct homeostasis of the immune response. Therefore, it is possible to hypothesize that variability at the CIITA-encoding locus, AIR-1, could constitute an additional source of susceptible traits to autoimmune diseases. Mutations at AIR-1/CIITA promoters could modulate expression of CIITA. Variations in CIITA expression could influence the qualitative and quantitative expression of MHC class II molecules at cell surface. We have analyzed sequence variation at AIR-1/CIITA promoters by PCR-SSCP in 23 IDDM and 30 RA patients compared to a sample of 19 unaffected normal controls and 16 unaffected IDDM family members, for a total of 88 Caucasian subjects from the Northeast of Italy. No sequence difference was found at the four AIR-1/CIITA promoters between autoimmune patients and normal controls. Moreover, the promoters resulted invariant within the entire group of 88 subjects analyzed, comprising patients and controls. This finding suggests a possible selective advantage in maintaining CIITA upstream regulatory sequences invariant.

Analysis of the yeast NSR1 gene and protein domain comparison between Nsr1 and human hnRNP type A1

The yeast nucleolar protein-encoding gene NSR1 was isolated by low-stringency screening of a yeast genomic library with the human heterogeneous nuclear ribonucleoprotein type A1 (hnRNP A1) cDNA probe, and was mapped to chromosome VII. RNA abundance was determined and the transcription start point and polyadenylation site were mapped. A comparison between the Nsr1 and hnRNP A1 proteins, based on homopolymer RNA binding to their structural domains in vitro, revealed a striking biochemical similarity. When the N-terminal, lysine- and arginine-rich domain of Nsr1 was removed, the truncated protein behaved similarly to hnRNP A1; furthermore, the two RRM (RNA recognition motif) domains of Nsr1 behaved in the same manner as the two RRM domains of hnRNP A1. The biochemical data, therefore, would support the hypothesis that the two RRM domains in hnRNP A1 and Nsr1 interact with RNA in a similar manner in both mammalian and yeast cells, respectively.

Fine mapping of a replication origin of human DNA

A highly sensitive procedure was developed for the identification of the origin of bidirectional DNA synthesis in single-copy replicons of mammalian cells. The method, which does not require cell synchronization or permeabilization, entails the absolute quantification, by a competitive PCR procedure in newly synthesized DNA samples, of the abundance of neighboring DNA fragments distributed along a given genomic region. This procedure was utilized for mapping the start site of DNA replication in a 13.7-kb region of human chromosome 19 coding for lamin B2, which is replicated immediately after the onset of S phase in HL-60 cells. Within this region, DNA replication initiates in a 474-bp area corresponding to the 3' noncoding end of the lamin B2 gene and the nontranscribed spacer between this gene and the 5' end of another highly transcribed one. This localization was obtained both in aphidicolin-synchronized and in exponentially growing HL-60 cells.

The gene for a novel human lamin maps at a highly transcribed locus of chromosome 19 which replicates at the onset of S-phase

A previously described human DNA fragment which is replicated early in S-phase of HL-60 cell DNA (C. Tribioli, G. Biamonti, M. Giacca, M. Colonna, S. Riva, and A. Falaschi, Nucleic Acids Res. 15:10211-10232, 1987) was used to screen a genomic library in lambda Ch28. A clone which contained a 13.7-kb insert (L30E) found to code for several transcripts was isolated. The transcription of L30E DNA exhibited a complex pattern and a tissue-specific and proliferation-dependent type of regulation. The data were consistent with two tandemly arranged transcription units, the 3' end of one separated from the 5' end of the other by a sequence of about 600 bp containing an active promoter. The isolation and sequencing of L30E-specific cDNAs permitted identification of two genes, one of which encoded a B-type human lamin (analogous to mouse lamin B2). L30E DNA was mapped by in situ hybridization at the G-negative subtelomeric band p13.3 of chromosome 19. Interestingly, in synchronized HL-60 cells, L30E DNA is replicated in the first minute of S-phase. Replication of the lamin gene early in S-phase may reflect a coupling between early replication and transcription of genes for S-phase-specific proteins such as lamins.

Novel islet, duct, and acinar cell markers defined by monoclonal autoantibodies from prediabetic BB rats

Novel islet cell, duct cell, and acinar cell markers have been identified by monoclonal autoantibodies (Maab) derived from prediabetic BB rats. Spleen cells from two rats that both developed diabetes after splenectomy were fused with mouse myeloma cells. A cellular immunoradiometric assay for differential reactivity toward the surface of two closely related, insulin- and non-insulin-producing rat islet tumor cell lines was used to select and clone several IgM-producing hybridomas. The supernatants were finally characterized by two-color immunofluorescence with islet hormone antisera on frozen sections of human, monkey, and rat pancreas. Maab EB52 stained PP cells, but also few A cells on rat pancreas. Maab CA812 identified a subpopulation of islet D cells on rat, human and monkey pancreas. Although the CA812-reactive antigen and somatostatin were coexpressed in most D cells in adult rat pancreas, only a few islet D cells were stained in the newborn pancreas. The CA812-reactive antigen was not detected in somatostatin-producing cells in the duct epithelium. Maab H37 and IF5 selectively stained acinar cells in rat, human, and monkey pancreas, whereas Maab DA39 identified the rat ductal epithelium including the scattered endocrine cells of the ducts. In summary, B lymphocytes producing autoantibodies to pancreatic endocrine, exocrine, and ductal markers are present in prediabetic BB rats and can be detected by use of transformed pluripotent islet cells as target. Such B lymphocytes can be immortalized to produce monoclonal antibodies to study their role in insulin-dependent diabetes mellitus pathogenesis and to clarify the development of the pancreas.

Autoantibodies to insulin do appear in non-diabetic patients with autoimmune disorders: comparison with anti-immunoglobulin antibodies and other autoimmune phenomena

Insulin- and anti-immunoglobulin-antibodies have been recently reported in pre-diabetic subjects: the former has been proposed as a predictive marker of Type I diabetes in non-diabetic-subjects. To evaluate the diabetes-related specificity of these antibodies, the presence of insulin autoantibodies, using a recently developed and highly sensitive competitive radioimmune assay, and of anti-immunoglobulin antibodies together with that of immune complexes and of other autoantibodies has been investigated in patients with organ- or non-organ-specific autoimmune diseases. One hundred and eleven serum samples were assayed from patients with Graves' disease, primary hypothyroidism, chronic autoimmune thyroiditis, Addison's disease, chronic autoimmune hepatitis, pernicious anemia, lupus erythematosus, and rheumatoid arthritis, together with 45 serum samples from normal subjects. From patients with autoimmune diseases, 32.4% of all sera revealed values of insulin autoantibodies above the limit of positivity (p less than 0.001); anti-immunoglobulin antibodies were present in 4.1% of patients (NS); immune complexes were found in 19.5% (NS) of all patients, but in 38% of patients with Graves' disease and chronic hepatitis (p less than 0.02). There was a trend for multiple autoantibody positivity to be associated with high levels of insulin autoantibodies (p less than 0.05). Thus, whereas contrary to expectation anti-immunoglobulin antibodies are not associated with non-diabetes-related autoimmune diseases, increased humoral immunoresponsiveness to endogenous insulin appears to be related to autoimmunity in general rather than restricted to Type I diabetes.

Increased levels of circulating immune complexes are not associated with diabetes in BB rats

Increased levels of circulating immune complexes (IC) have been described in insulin-dependent diabetic (IDD) patients at the time of diagnosis. The aim of the present study was to test whether the spontaneously diabetic BB rat had changes in IC levels at different ages prior to and at onset of IDDM as compared with diabetes resistant BB rats and normal Wistar Furth rats. The IC levels were related to serum IgG concentration as well as to total peripheral blood lymphocyte counts. Three groups of rats with 12 animals in each were followed: Diabetes-prone, lymphopenic (DP) BB rats with an expected high incidence of diabetes, diabetes-resistant (DR) BB rats from the non-diabetic w-subline, and Wistar Furth rats. Blood samples collected on 12, 22, 29, 43, 71, and 99 days of age were analyzed for IC, detected in a solid phase C1q assay, serum IgG levels, and peripheral blood lymphocytes. Diabetes developed in 8/12 (66%) DP BB rats between 70 and 93 days of age while none of the DR BB rats developed diabetes. The levels of IC tended to increase with age in all three groups of rats and did not differ between DP BB and Wistar rats whereas DR BB rats had significantly higher levels (p less than 0.05-0.01) at all ages. The profile of serum IgG was similar in all rats showing a high level at 12 days of age and a nadir at day 29 followed by an increase from day 43 until the end of the follow-up period.(ABSTRACT TRUNCATED AT 250 WORDS)

Anti-goat immunoglobulin antibodies in diabetic children at diagnosis and follow-up: comparison with islet cell antibodies and other autoantibodies

The presence of antibodies reacting with human as well as animal immunoglobulins in sera from recent onset Type I diabetic patients has been recently demonstrated by some of our group. In the present study, the occurrence of these antibodies has been evaluated in sera from 19 Type I diabetic patients, at diagnosis and at follow-up within three years, and from 26 normal subjects, and has also been compared with the presence of islet cell antibodies and other organ-specific autoantibodies. A solid-phase radioimmunoassay has been used: serum was incubated in goat immunoglobulin-coated wells and the binding of 125-I-anti-human immunoglobulin antibodies was evaluated. Anti-goat immunoglobulin antibodies were above the 90th percentile of normal values in all diabetic patients at diagnosis (median, interquartile range, in micrograms 125I-antibody bound/1 serum: 83, 77.5-88, versus 51.5, 44.5-62 in normal subjects, P less than 0.001) and significantly declined with time after diagnosis (P less than 0.001). Islet cell antibodies were present in 79% of patients at diagnosis, whereas at least one other auto-antibody was found in 21% of patients. In the follow-up study the decline in anti-goat immunoglobulin antibody levels was different from that of islet cell antibody positivity. A circulating immunoglobulin reacting with other immunoglobulins is thus present in the early stages of Type I diabetes and may well play a part in the complex immunopathogenetic interactions.

A simple assay for the detection of antibodies to endocrine islet cell surface antigens

A simple and sensitive immunoradiometric assay for the detection of islet cell surface antibodies (CIRMA) has been developed. Live, transformed islet cells derived from a liver metastasis of a transplantable islet cell tumor were grown in removable microtiter wells and incubated with antibody. Cell-bound antibodies were quantitated using 125I-labelled second antibodies. The assay was used to detect islet cell antibodies present in sera from non-diabetic and diabetic BB rats and proved to be particularly effective for screening hybridoma supernatants in order to identify monoclonal antibodies recognizing islet cell surface antigens.

The relationship of soluble immune complexes, insulin antibodies and insulin-anti-insulin complexes to platelet and coagulation factors in type 1 diabetic patients with and without proliferative retinopathy

The possible correlation between soluble immune factors and platelet and coagulation factors has been evaluated in Type 1 diabetic patients with and without proliferative retinopathy, and in non-diabetic controls. Soluble immune complexes, platelet factor IV (PF4), beta-thromboglobulin, fibrinogen, factor VIII related antigen and anti-thrombin III were significantly increased in Type 1 diabetic patients with retinopathy as compared to non-diabetic controls. Fibrinogen and anti-thrombin III were also higher in those patients with retinopathy compared to those without retinopathy. A significant correlation was found between positive values of soluble immune complexes and increased levels of PF4 and beta-thromboglobulin in diabetic patients with retinopathy. The presence of soluble immune complexes and insulin-anti-insulin complexes was associated with a significantly greater number of elevated haemostatic factors in retinopathic patients. Our findings suggest that the interaction of platelets and soluble immune complexes or insulin-anti-insulin complexes may be pathologically relevant to the development of diabetic retinopathy.