epithelial cells

Examples of epithelial cells in the following topics:

• DNA Oncogenic Viruses

  • This virus infects B cells of the immune system and epithelial cells.
  • In permissive cells, all parts of the viral genome are expressed.
  • This leads to viral replication, cell lysis and cell death.
  • In cells that are non-permissive for replication, viral DNA is usually, but not always, integrated into the cell chromosomes at random sites.
  • Papillomas are benign growths, such as warts, of epithelial cells.

• Other Diseases and Epstein-Barr Virus

  • EBV infects B cells of the immune system and epithelial cells.
  • Once EBV enters the cell, the viral capsid dissolves and the viral genome is transported to the cell nucleus.
  • EBV can undergo lytic replication in both B cells and epithelial cells.
  • In epithelial cells, lytic replication often directly follows viral entry entry.
  • EBV can latently persist within B cells and epithelial cells, but different latency programs are possible in the two types of cells.

• Cryptosporidiosis

  • The transmission of Cryptosporidium is based on successful ingestion of oocysts which are able to implant and infect the epithelial tissue of the intestine, hence, the gastrointestinal symptoms associated with cryptosporidiosis.
  • The trophozoites then develop into Type 1 and Type 2 merozoites which can either cause auto infection (Type 1) or undergo releasal and attach the epithelial cells (Type 2).
  • The oocysts can initiate infections by attaching to the brush border of the small intestine and attacking the epithelial cells.

• Whooping Cough

  • Bordetella pertussis infects its host by colonizing lung epithelial cells.
  • The bacterium contains a surface protein, filamentous haemagglutinin adhesin, which binds to the sulfatides found on the cilia of epithelial cells.

• Type III and Type IV Secretion

  • Type III and IV secretion systems are utilized by pathogenic bacteria to transfer molecules from the bacterial cell to the host cell.
  • The bacterial conjugation machinery allows transfer of genetic material to occur via direct cell-to-cell contact or by a bridge-like apparatus between the two cells.
  • H. pylori, most commonly associated with stomach ulcers, attaches itself to epithelial cells within the stomach, then via a type IV secretion system, injects a secretory molecule.
  • The secretory molecule injected into the epithelial cells is an inflammation-inducing agent derived from their own cellular wall.
  • Peptidoglycan is not the only secretory molecule transferred to the stomach epithelial cells but additional proteins, such as CagA, which function in disruption of host cell cellular activities can be transferred as well .

• Biofilms and Infections

  • A biofilm is an aggregate of microorganisms in which cells adhere to each other on a surface.
  • The patients with biofilms were shown to have been denuded of cilia and goblet cells, unlike the controls without biofilms who had normal cilia and goblet cell morphology.
  • Recent studies have demonstrated that it utilizes two distinct mechanisms for entry into human urethral and cervical epithelial cells involving different bacterial surface ligands and host receptors.
  • There is evidence for the formation of gonococcal biofilms on human cervical epithelial cells during natural disease.
  • Evidence also suggests that the outer membrane blebbing by the gonococcus is crucial in biofilm formation over human cervical epithelial cells.

• Dendritic Cells

  • Dendritic cells are immune cells that function to process antigens and present them to T cells.
  • The function of epithelial dendritic cells is to capture microbial protein antigens and to transport the antigens to draining lymph nodes.
  • Mature dendritic cells reside in the T cell zones of the lymph nodes, and in this location they display antigens to T cells.
  • Dendritic cells are constantly in communication with other cells in the body.
  • This communication can take the form of direct cell-to-cell contact based on the interaction of cell-surface proteins.

• Direct Damage

  • The pathogenic organism must exhibit specific characteristics that promote its growth into a host cell including, but not limited to, the ability to invade, colonize, and attach to host cells.
  • Often times, bacteria will directly attach themselves to host cells and utilize nutrients from the host cell for their own cellular processes.
  • The production of these destructive products results in the direct damage of the host cell.
  • The waste products of the microbes will also damage to the cell.
  • The enzymes, capable of digesting fibrin, will open an area within the epithelial cells and promote invasion of the bacteria into the tissues.

• Replicative Cycle of Influenza A

  • Influenza viruses bind through hemagglutinin onto sialic acid sugars on the surfaces of epithelial cells, typically in the nose, throat, and lungs of mammals, and the intestines of birds (Step 1 in infection figure ).
  • Once inside the cell, the acidic conditions in the endosome cause two events to happen:
  • Hemagglutinin and neuraminidase molecules cluster into a bulge in the cell membrane.
  • As before, the viruses adhere to the cell through hemagglutinin; the mature viruses detach once their neuraminidase has cleaved sialic acid residues from the host cell.
  • After the release of new influenza viruses, the host cell dies.

• Phagocyte Migration and Phagocytosis

  • Phagocytosis is the engulfment of foreign material in a body by a specialized cell type.
  • Phagocytosis is the process by which a cell takes in particles such as bacteria, parasites, dead host cells, and cellular and foreign debris.
  • Dendritic cells and macrophages, on the other hand, are not so fast, and phagocytosis can take many hours in these cells.
  • Other signals called vasodilators loosen the junctions connecting endothelial cells, allowing the phagocytes to pass through the wall.
  • Neutrophils travel across epithelial cell-lined organs to sites of infection, and although this is an important component of fighting infection, the migration itself can result in disease-like symptoms.