Prevalence of coexisting autoimmune thyroidal diseases in coeliac disease is decreasing.

BACKGROUND: Coeliac disease (CD) is associated with an increased risk of other immune-mediated conditions. Aim: To investigate the prevalence of coexistent immune-mediated diseases in CD patients, and changes in the prevalence of autoimmune thyroidal diseases over the last 50 years. METHODS: Medical record data were collected retrospectively from 749 CD patients in Ireland. Prevalence of autoimmune diseases was compared with previously published results from general populations. Patients were divided into four groups based on the year of diagnosis to analyse changes in the prevalence of autoimmune thyroidal disease over time. RESULTS: Median age at the time of CD diagnosis was 56 years (range 18-91 years). A total of 233 (31.1%) patients had a coexistent immune-mediated condition (IMC). Autoimmune thyroidal diseases were seen in 149 (19.9%) patients, hypothyroidism in 110 (14.7%), type 1 diabetes in 27 (3.6%), psoriasis in 20 (2.7%), inflammatory bowel disease in 14 (1.9%) and rheumatoid arthritis in 12 (1.6%). All conditions were more common in CD patients than in the general population. Type 1 diabetes was diagnosed mainly before CD, whereas there was no such trend in other conditions. Autoimmune thyroidal diseases became less common in female CD patients over time. CONCLUSIONS: Prevalence of autoimmune diseases is increased in adult CD patients compared with the general population. However, concomitant autoimmune thyroidal diseases became less common over time in women.

Protein kinase C delta is a substrate of tissue transglutaminase and a novel autoantigen in coeliac disease.

Post-translational modification of proteins by deamidation or transamidation by tissue transglutaminase (tTG) has been suggested as a possible mechanism for the development of autoimmunity. Sequence analysis of protein kinase C delta (PKCδ) identified an amino acid motif that suggested the possibility that PKCδ was a glutamine substrate of tTG and MALDI-TOF analysis of synthesised peptides from PKCδ proved that this was the case. Polymerisation experiments using recombinant tTG and biotinylated hexapeptide substrate incorporation assays demonstrated that PKCδ is a substrate for tTG-mediated transamidation. Elevated levels of anti-PKCδ antibodies were detected in sera from patients with coeliac disease (p<0.0001) but not from patients with other autoimmune disorders. These data suggest that a subset of patients with coeliac disease produce autoantibodies against PKCδ and that this response may stem from a tTG-PKCδ substrate interaction.

Coeliac disease autoantibodies mediate significant inhibition of tissue transglutaminase.

The detection of antibodies directed against tissue transglutaminase (tTG) in serum is a sensitive and specific test for suspected coeliac disease. tTG is a ubiquitous, multifunctional enzyme that has been implicated in many important physiological processes as well as the site-specific deamidation of glutamine residues in gluten-derived peptides. This modification of gluten peptides facilitates their binding to HLA-DQ2, which results in amplification of the T-cell response to gluten. The purpose of this study was to investigate the possibility that patient IgA autoantibodies directed against tTG interfere with the crosslinking activity of the enzyme. IgA autoantibodies against tTG were isolated/depleted from patient serum and tested for their capacity to interfere with tTG activity in vitro using a sensitive fluorescence-based activity assay. We have demonstrated that autoantibodies cause significant inhibition of tTG-mediated crosslinking at equimolar and 2:1 ratios of antibody to enzyme.

Signaling by Toll-like receptors 8 and 9 requires Bruton's tyrosine kinase.

Toll-like receptors (TLRs) are a primary surveillance system for the detection of pathogens and are crucial to the activation of host defense. TLR7 and TLR8 sense single-stranded RNA from viruses or host ribonucleoproteins and synthetic imidazoquinolines such as R848, whereas TLR9 senses unmethylated CpG motifs in viral and bacterial DNA and in host DNA. Here we report the endogenous interaction between Brutons's tyrosine kinase (Btk) and human TLR8 and TLR9 in the monocytic cell line THP1. We also show that R848, single-stranded RNA, and CpGB-DNA activate Btk in THP1 cells as shown by phosphorylation of the tyrosine 223 residue of Btk and also by increased autokinase activity. We demonstrate that Btk is required for NFkappaB activation, participating in the pathway to increased phosphorylation of p65 on serine 536 activated by TLR8 and TLR9. Finally we demonstrate that peripheral blood mononuclear cells from patients with X-linked agammaglobulinaemia (XLA) that have dysfunctional Btk are impaired in the induction of interleukin-6 by CpGB-DNA. This study therefore establishes Btk as a key signaling molecule that interacts with and acts downstream of TLR8 and TLR9. Lack of functioning Btk in XLA patients downstream of TLR8 and TLR9 might explain the susceptibility of XLA patients to viral infections.

A genome-wide association study for celiac disease identifies risk variants in the region harboring IL2 and IL21.

We tested 310,605 SNPs for association in 778 individuals with celiac disease and 1,422 controls. Outside the HLA region, the most significant finding (rs13119723; P = 2.0 x 10(-7)) was in the KIAA1109-TENR-IL2-IL21 linkage disequilibrium block. We independently confirmed association in two further collections (strongest association at rs6822844, 24 kb 5' of IL21; meta-analysis P = 1.3 x 10(-14), odds ratio = 0.63), suggesting that genetic variation in this region predisposes to celiac disease.

Mutagenesis of the catalytic triad of tissue transglutaminase abrogates coeliac disease serum IgA autoantibody binding.

BACKGROUND AND AIMS: Tissue transglutaminase (tTG) is an autoantigen in coeliac disease and the related disorder, dermatitis herpetiformis. The detection of autoantibodies directed against tTG is a highly specific marker of coeliac disease; however, it is unclear if there is a role for these autoantibodies in the disease process. The aim of this study was to investigate whether the catalytic triad of tTG is targeted by coeliac disease autoantibodies. METHODS: A full-length wild-type recombinant tTG and a novel site-directed mutagenic variant lacking the catalytic triad were produced in Escherichia coli. Serum samples from 61 biopsy-proven coeliac disease and 10 dermatitis herpetiformis patients were tested for their recognition of both antigens in enzyme-linked immunosorbent assay. RESULTS: Although IgA autoantibodies from sera of patients with coeliac disease and dermatitis herpetiformis bound wild-type tTG well, a dramatic decrease in binding to the mutant tTG was observed with a mean reduction of 79% in coeliac disease and 58% in dermatitis herpetiformis samples. IgG anti-tTG antibodies did not show a similar pattern of reduction, with no overall difference in recognition of the wild-type or mutant tTGs. CONCLUSIONS: These results suggest that the IgA anti-tTG response in coeliac disease and dermatitis herpetiformis is focused on the region of tTG responsible for its transamidation and deamidation reactions, whereas the IgG response may target other regions of the enzyme.