Microbiota are microscopic organisms such as viruses, bacteria, archaea, and eukaryotes that influence human health through a commensal interaction. Location of microbiota can be internal or external such as the gut, mouth, placenta, skin, and vagina. These microbes are classified into four major phyla: Firmicutes, Bacteriodetes, Actinobacteria, and Proteobacteria. Microorganisms in the Firmicute phylum are typically Gram positive bacteria, either rod-shaped or spherical and function as obligate or facultative anaerobes. Firmicutes are predominately found in the vagina. Microorganisms under the phylum Bacteriodetes are typically Gram negative bacteria and are strictly anaerobes. These are mainly found in the gut microbiome including 100 trillion
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The goblet cells of the intestinal epithelium secrete layers of mucus that prevent microbiota from contacting the epithelium too closely. The outer layer of mucus houses a large concentration of microbes whereas the inner mucus layer cannot be penetrated. However, because of the huge diversity and quantity of gut microbiota there is moments when the inner mucous is breached. The bacteria that have migrated into the inner mucus layer is recognized by innate immune cells termed dendritic cells. Dendritic cells contain pattern recognition receptors (PRRs) such as Toll-like receptors (TLRs) that recognize microbial associated molecular patterns (MAMPs). Both pathogen and commensal microbiota contain MAMPs such as peptidoglycans, lipopolysaccharides and flagella. Activation of TLRs sets off a signalling cascade of nuclear factor-kappa B (NF-kB) to initiates the production of cytokines that results in an inflammatory response (20). Dendritic cell also sample bacterium and transfers it to the mesenteric lymph nodes through the lymphatics of the intestine. Once the activated dendritic cell reaches the Peyer’s patches they interact with B-cells to produce Immunoglobulin A (IgA). IgA producing B-cells are brought back to the lamina propria of the intestinal epithelial where they differentiate into IgA plasma cells. These plasma cells secrete dimerized IgA from the Lamina propria to the inner mucous layer where they interact with the antigens present on bacteria, neutralizing and preventing their invasion into the epithelium. Bacteria that have crossed the epithelial cells into the Lamina propria can also be phagocytosed by macrophages that contain PRRs. Finally, the immune system also responds by secreting antimicrobial α-defensin protein and the antimicrobial lectin RegIII훾. It has been noted that α-defensin can alter microbial composition whereas RegIII훾’s function is to monitor
The goblet cells of the intestinal epithelium secrete layers of mucus that prevent microbiota from contacting the epithelium too closely. The outer layer of mucus houses a large concentration of microbes whereas the inner mucus layer cannot be penetrated. However, because of the huge diversity and quantity of gut microbiota there is moments when the inner mucous is breached. The bacteria that have migrated into the inner mucus layer is recognized by innate immune cells termed dendritic cells. Dendritic cells contain pattern recognition receptors (PRRs) such as Toll-like receptors (TLRs) that recognize microbial associated molecular patterns (MAMPs). Both pathogen and commensal microbiota contain MAMPs such as peptidoglycans, lipopolysaccharides and flagella. Activation of TLRs sets off a signalling cascade of nuclear factor-kappa B (NF-kB) to initiates the production of cytokines that results in an inflammatory response (20). Dendritic cell also sample bacterium and transfers it to the mesenteric lymph nodes through the lymphatics of the intestine. Once the activated dendritic cell reaches the Peyer’s patches they interact with B-cells to produce Immunoglobulin A (IgA). IgA producing B-cells are brought back to the lamina propria of the intestinal epithelial where they differentiate into IgA plasma cells. These plasma cells secrete dimerized IgA from the Lamina propria to the inner mucous layer where they interact with the antigens present on bacteria, neutralizing and preventing their invasion into the epithelium. Bacteria that have crossed the epithelial cells into the Lamina propria can also be phagocytosed by macrophages that contain PRRs. Finally, the immune system also responds by secreting antimicrobial α-defensin protein and the antimicrobial lectin RegIII훾. It has been noted that α-defensin can alter microbial composition whereas RegIII훾’s function is to monitor