To respond or not to respond - a personal perspective of intestinal tolerance

For many years, the intestine was one of the poor relations of the immunology world, being a realm inhabited mostly by specialists and those interested in unusual phenomena. However, this has changed dramatically in recent years with the realization of how important the microbiota is in shaping immune function throughout the body, and almost every major immunology institution now includes the intestine as an area of interest. One of the most important aspects of the intestinal immune system is how it discriminates carefully between harmless and harmful antigens, in particular, its ability to generate active tolerance to materials such as commensal bacteria and food proteins. This phenomenon has been recognized for more than 100 years, and it is essential for preventing inflammatory disease in the intestine, but its basis remains enigmatic. Here, I discuss the progress that has been made in understanding oral tolerance during my 40 years in the field and highlight the topics that will be the focus of future research

Association Analysis of the Extended MHC Region in Celiac Disease Implicates Multiple Independent Susceptibility Loci

Celiac disease is a common autoimmune disease caused by sensitivity to the dietary protein gluten. Forty loci have been implicated in the disease. All disease loci have been characterized as low-penetrance, with the exception of the high-risk genotypes in the HLA-DQA1 and HLA-DQB1 genes, which are necessary but not sufficient to cause the disease. The very strong effects from the known HLA loci and the genetically complex nature of the major histocompatibility complex (MHC) have precluded a thorough investigation of the region. The purpose of this study was to test the hypothesis that additional celiac disease loci exist within the extended MHC (xMHC). A set of 1898 SNPs was analyzed for association across the 7.6 Mb xMHC region in 1668 confirmed celiac disease cases and 517 unaffected controls. Conditional recursive partitioning was used to create an informative indicator of the known HLA-DQA1 and HLA-DQB1 high-risk genotypes that was included in the association analysis to account for their effects. A linkage disequilibrium-based grouping procedure was utilized to estimate the number of independent celiac disease loci present in the xMHC after accounting for the known effects. There was significant statistical evidence for four new independent celiac disease loci within the classic MHC region. This study is the first comprehensive association analysis of the xMHC in celiac disease that specifically accounts for the known HLA disease genotypes and the genetic complexity of the region

Celiac disease: how complicated can it get?

In the small intestine of celiac disease patients, dietary wheat gluten and similar proteins in barley and rye trigger an inflammatory response. While strict adherence to a gluten-free diet induces full recovery in most patients, a small percentage of patients fail to recover. In a subset of these refractory celiac disease patients, an (aberrant) oligoclonal intraepithelial lymphocyte population develops into overt lymphoma. Celiac disease is strongly associated with HLA-DQ2 and/or HLA-DQ8, as both genotypes predispose for disease development. This association can be explained by the fact that gluten peptides can be presented in HLA-DQ2 and HLA-DQ8 molecules on antigen presenting cells. Gluten-specific CD4+ T cells in the lamina propria respond to these peptides, and this likely enhances cytotoxicity of intraepithelial lymphocytes against the intestinal epithelium. We propose a threshold model for the development of celiac disease, in which the efficiency of gluten presentation to CD4+ T cells determines the likelihood of developing celiac disease and its complications. Key factors that influence the efficiency of gluten presentation include: (1) the level of gluten intake, (2) the enzyme tissue transglutaminase 2 which modifies gluten into high affinity binding peptides for HLA-DQ2 and HLA-DQ8, (3) the HLA-DQ type, as HLA-DQ2 binds a wider range of gluten peptides than HLA-DQ8, (4) the gene dose of HLA-DQ2 and HLA-DQ8, and finally,(5) additional genetic polymorphisms that may influence T cell reactivity. This threshold model might also help to understand the development of refractory celiac disease and lymphoma

Intravenous hydrocortisone premedication reduces antibodies to infliximab in Crohn's disease: a randomized controlled trial

BACKGROUND & AIMS: We assessed the relationship between antibodies to infliximab (ATI) and the loss of response postinfliximab, infusion reactions and, in a randomized trial, investigated whether intravenous hydrocortisone premedication can reduce ATI. METHODS: Initially, we prospectively evaluated clinical response, adverse events, and ATI levels in 53 consecutive patients with Crohn's disease who received 199 infliximab (5 mg/kg) infusions. Subsequently, 80 patients with Crohn's disease were randomized to intravenous hydrocortisone 200 mg or placebo immediately before their first and subsequent infliximab infusions. The primary endpoint was reduction in median ATI levels at week 16. Analysis was by intention to treat. RESULTS: Nineteen of our initial 53 patients (36%) developed ATI, including all 7 patients with serious infusion reactions (median ATI level, 19.6 microg/mL). Eleven of 15 patients (73%) who lost their initial response were ATI positive compared with none of 21 continuous responders, (8.9 vs. 0.7 microg/mL, P < 0.0001). Administering a second infusion within 8 weeks of the first (OR, 0.13; 95% CI, 0.03-0.5; P = 0.0007) or concurrent immunosuppressants (OR, 0.19; 95% CI, 0.04-1.03; P = 0.007) significantly reduced ATI formation. In the placebo-controlled trial, ATI levels were lower at week 16 among hydrocortisone-treated patients (1.6 vs. 3.4 microg/mL, P = 0.02), and 26% of hydrocortisone-treated patients developed ATI compared with 42% of placebo-treated patients, P = 0.06. CONCLUSIONS: Loss of initial response and infusion reactions post-infliximab is strongly related to ATI formation and level. Administering a second infusion within 8 weeks of the first and concurrent immunosuppressant therapy significantly reduce ATI formation. Intravenous hydrocortisone premedication significantly reduces ATI levels but does not eliminate ATI formation or infusion reactions

Clinical experience with infliximab therapy in 100 patients with Crohn's disease

OBJECTIVE: The aim of this study was to assess our clinical experience with infliximab, a monoclonal antitumor necrosis factor antibody, following its approval for treatment of refractory Crohn's disease (CD). METHODS: We followed 100 consecutive patients with CD (53 women and 47 men; mean age, 41 yr) who received a total of 233 infliximab (5 mg/kg) infusions. Adverse events were noted and clinical response assessed every 2 wk for 6 months after each infusion using the Harvey Bradshaw Index (HBI) for active disease, the Perianal Disease Activity Index (PDAI) for fistulous disease, and steroid withdrawal rates for steroid-sparing efficacy. RESULTS: Indications for therapy were active disease (n = 57), perianal fistulous disease (n = 33), and steroid dependency (n = 10). Significant infusion reactions occurred in 16 patients (6.9% of infusions) including anaphylactic shock in one patient. Fourteen patients experienced infectious adverse events, 13 of whom were on concurrent steroids. Sixty percent of patients with active disease experienced > or = 50% HBI reduction at 2 wk; mean duration of response, 8.2 wk. Three of 26 first-time nonresponders with active disease (12%) responded to a second infusion. Sixty-nine percent of patients with fistulous disease experienced >50% reduction in their PDAI at 2 wk; mean duration of response, 10.9 wk. Four of 10 steroid-dependent patients (40%) discontinued steroid therapy, one of whom recommenced steroid therapy at 24 wk. CONCLUSIONS: Our clinical response rates mirror the efficacy reported in the controlled trials for active and fistulous disease. Steroid-sparing efficacy was seen in 40% of steroid-dependent patients. Concurrent steroids did not reduce the risk of significant infusion reactions (6.9%), but did increase the risk of infections