Goblet cell

Goblet cells are found scattered among the epithelial lining of organs, such as the intestinal and respiratory tracts. They are found inside the trachea, bronchi, and larger bronchioles in the respiratory tract, small intestines, the large intestine, and conjunctiva in the upper eyelid. In the conjunctiva goblet cells are a source of mucin in tears and they also secrete different types of mucins onto the ocular surface. In the lacrimal glands, mucus is synthesized by acinar cells instead. Microanatomy Goblet cells are simple columnar epithelial cells, having a height of four times that of their width. The cytoplasm of goblet cells tends to be displaced toward the basal end of the cell body by the large mucin granules, which accumulate near the apical surface of the cell along the Golgi apparatus, which lies between the granules and the nucleus. This gives the basal part of the cell a basophilic staining because of nucleic acids within the nucleus and rough endoplasmic reticulum staining with hematoxylin. Mucin within the granules stains pale in routine histology sections, primarily because these carbohydrate-rich proteins are washed out in the preparation of microscopy samples. However, they stain easily with the PAS staining method, which colours them magenta. In mucicarmine stains, deep red mucin is found within goblet cell bodies. Goblet cells can be seen in the examples below as the larger, more pale cells. File:Gray1062.png|An intestinal gland from the human intestine with goblet cells visible File:Gobletcell.jpg|Goblet cell in ileum File:MultiPhotonExcitation-Fig10-doi10.1186slash1475-925X-5-36.JPEG|Section of mouse intestine, mucus of goblet cells in blue File:Goblet cells.jpg|Goblet cells in large intestine ==Function==

The main role of goblet cells is to secrete mucus in order to protect the mucous membranes where they are found. Goblet cells accomplish this by secreting mucins, large glycoproteins formed mostly by carbohydrates. The gel-like properties of mucins are given by its glycans (bound carbohydrates) attracting relatively large quantities of water. On the inner surface of the human intestine, it forms a 200 μm thick layer (less in other animals) that lubricates and protects the wall of the organ. Distinct forms of mucin are produced in different organs: while MUC2 is prevalent in the intestine, MUC5AC and MUC5B are the main forms found in the human airway. In the airway, mucus is swept by the cilia of the respiratory epithelium, in a process called mucociliary clearance, and propelled out of the lungs and into the pharynx, which results in the removal of debris and pathogens from the airway. MUC5AC is overexpressed in hypersensitivity pneumonitis. Secretion may be stimulated by irritants such as dust and smoke, especially in the airway. but these are distinguished histologically from goblet cells. Role in oral tolerance Oral tolerance is the process by which the immune system is prevented from responding to antigen derived from food products, as peptides from food may pass into the bloodstream via the gut, which would in theory lead to an immune response. A paper published in Nature in 2012 has shed some light on the process and implicated goblet cells as having a role in the process. It was known that CD103-expressing dendritic cells of the lamina propria had a role to play in the induction of oral tolerance (potentially by inducing the differentiation of regulatory T cells), and this paper suggests that the goblet cells act to preferentially deliver antigen to these CD103+ dendritic cells. ==Clinical significance==

Allergic asthma The excessive mucus production seen in allergic asthma patients is due to goblet cell metaplasia, the differentiation of airway epithelial cells into mucin producing goblet cells. These cells produce the thick mucins MUC5AC and MUC5B, which clog the airway, leading to the airflow obstruction characteristic of asthma. Binding of IL-13 causes phosphorylation of tyrosine residues at the IL-4Rα. 15-lipoxygenase acts by binding to phospholipids and yields hydroperoxy and epoxy metabolites. The main treatment for localized goblet cells tumors is removal of the appendix, and sometimes removal of the right hemicolon is also performed. Disseminated tumors may require treatment with chemotherapy in addition to surgery. Colonic mucosa Bile acids are a significant factor in the etiology of colorectal cancer. Bile acids induce apoptosis in goblet cells of the colonic mucosa at bile acid concentrations that are comparable to those found in fecal water after high fat-meals. An association was observed between resistance to bile acid-induced apoptosis in goblet cells and colon cancer risk. Some treatments that use anti-IL-13 monoclonal antibodies include tralokinumab, and lebrikizumab. These treatments have shown improvements in asthma patients, yet there are still limitations to the use of anti-IL-13 monoclonal antibodies. Dupilumab is a newer drug that targets the shared receptor of IL-4 and IL-13, IL4Rα. Since IL-4 and IL-13 have interrelated biological activities, Dupilumab is a more effective form of treatment as it targets both interleukins. ==History==

The cells were first noted by Henle in 1837 when studying the lining of the small intestine, seen to be mucus producing by Leydig in 1857 (who was examining the epidermis of fish), and were given their name by Schulze in 1867, Schulze chose the descriptive name "goblet" because of the shape of the cell, rather than a functional name, as he remained uncertain as to the mucus-producing function of the cell. == See also ==