# Pro-Pre and Postbiotic in Celiac Disease
## 1 Introduction  
Celiac disease (CD) is a common systemic disease that primarily affects the small intestine [1], due to the abnormal response of the immune system to gluten ingestion. It happens in subjects with genetic susceptibility (HLA-DQ2/DQ8 positivity and non-HLA genes) and under the influence of environmental triggers, including, a part from gluten, viral infections and intestinal microbiota dysbiosis [2]. Although 30-40% of the world population carry the HLA DQ2/DQ8 genotype, only 1-1.5% of them express the CD phenotype, which means that other genes together with other environmental factors may take part [2, 3]. Typically, the inflammation in CD includes an increased intraepithelial lymphocyte (IEL) count, most often >25/100 cells [4, 5]. Other features of CD are the presence of an adaptive T-cell-mediated response to gluten [6, 7] and of specific endomysial antibodies (EMA, also called AEA), anti-tissue transplantinase antibodies (TTG, a-tTG, TTA), and/or deamidated antigliadin antibodies (DGP) that play an important role in the serological work-up for CD. These antibodies strongly support the diagnosis of CD. In children, the intestinal biopsy is necessary where the antibody title is low and symptoms are absent. In paediatric patients with high tTG-IgA, ESPGHAN recommends that the decision whether or not to perform duodenal biopsies should be made during a shared decision making process between the paediatric gastroenterologist/coeliac disease specialist, the parent(s)/carer(s), and if appropriate, the child and any way when patients are on a gluten-containing diet [8]. The diagnosis is confirmed by the finding of an intestinal atrophy with shortening of the intestinal will and increase of the crypt proliferation. Gluten ispoorly digested in the human intestine with or without CD. Undigested gluten peptides cross intact the mucosa of the small intestine. In the submuc of the small intestine the human enzyme transglutaminase 2 (tTG) deamidates gluten peptides, leading to an increase in the affinity binding to human leucocyte antigen (HLA) DQ2 and HLA DQ8 molecules, subsequently triggering an inflammatory reaction in patients with CD [7]. The only treatment currently available in CD is a gluten-free diet for life. Recently, in CD, a role for the gut microbiota, has been described. There are several cross-sectional studies comparing microbiota in patients and controls, which describe a dysbiosis in CD patients before, and after, the gluten free diet. The aim of this review is to describe the most recent literature on pro-, pre and post-biotic in CD (See Figure 1). Pro-biotics are microorganisms, most of which are bacteria similar and/or the same to the beneficial bacteria that occur naturally in the human gut. Pro-biotics have been widely studied in a variety of gastrointestinal diseases. Pro-biotics have an important role in the maintenance of immunologic equilibrium in the gastrointestinal tract through the direct interaction with immune cells. Pro-biotic effectiveness can be species-, dose- and disease-specific, and the duration of therapy depends on the clinical indication. Dietary fibers can be metabolized by microbes in the gastrointestinal tract. Human food enzymes are unable to digest most complex carbohydrates and plant polysaccharides. Instead, these polysaccharides are metabolized by microbes that generate short-chain fatty acids (SCFAs), including acetate, propionate and butyrate. Post-biotics are known as \"non-viable probiotics\", \"inactivate probiotics\" or \"ghost probiotics\" and refer to both non-viable microbial cells and soluble factors secreted by live bacteria or released after their lysis, including various cell surface components, lactic acid, short-chain fatty acids (SCFAs) and bioactive peptides among other metabolites. When administrated in sufficient amounts, these may contribute to the improvement of host health, even though the exact mechanisms are not yet well-known. The bacterial inactivation usually occurs by a mild heat treatment.