mast cells

Examples of mast cells in the following topics:

• Type I (Anaphylactic) Reactions

  • Exercise or temperature (either hot or cold) may also trigger anaphylaxis by causing tissue cells known as mast cells to release chemicals that start the allergic reaction.
  • People who have disorders caused by too many mast cells in their tissues (mastocytosis) or who are wealthier are at increased risk.
  • It results from the release of inflammatory mediators and cytokines from mast cells and basophils.
  • The combination of IgE bound to the antigen activates FcεRI receptors on mast cells and basophils.
  • The mast cells and basophils react by releasing inflammatory mediators such as histamine.

• Phagocytes

  • The main types of phagocytes monocytes, macrophages, neutrophils, tissue dendritic cells, and mast cells.
  • Mast cells are PMN granulocytes with toll-like receptors that tend to trigger inflammatory responses.
  • Mast cells express MHC class II molecules and can participate in antigen presentation; however, the mast cell's role in antigen presentation is not very well understood.
  • Mast cells can consume and kill and process their antigens.
  • Monocytes differentiate into dendritic cells and macrophages, while mast cells and neutrophils are in a separate group of PMN granuolcytes as well.

• Types of Adaptive Immunity

  • Cell mediated immunity is controlled by type 1 helper T-cells (Th1) and cytotoxic T-cells.
  • Helper-T cells facilitate the immune response by guiding cytotoxic T-cells to pathogens or pathogen-infected cells, while the cytotoxic T-cells will kill the pathogens or pathogen-infected cells.
  • Humoral immunity refers to the component of the adaptive immune response that is caused by B cells, antibodies, and type 2 helper T-cells (Th2), as well as circulating mast cells and eosinophils to a smaller extent.
  • Mast cells and eosinophils are considered to be part of the humoral immune system because they can be sensitized towards certain antigens through circulating immunoglobin E (IgE), which is a specific type of antibody produced by B cells.
  • IgE will bind to the mast cells and eosinophils when an antigen is detected, using a type of Fc receptor on the mast cell or eosinophil that has a high binding affinity with IgE.

• Hypersensitivities

  • The constant domain of the IgE molecules interacts with mast cells embedded in connective tissues.
  • Upon subsequent exposure to the same allergen, IgE molecules on mast cells bind the antigen via their variable domains, stimulating the mast cell to release the modified amino acids histamine and serotonin.
  • On first exposure to an allergen, an IgE antibody is synthesized by plasma cells in response to a harmless antigen.
  • The IgE molecules bind to mast cells.
  • On secondary exposure, the mast cells release histamines and other modulators that affect the symptoms of allergy.

• Inflammation

  • The most common short term mediators are histamine and seratonin from mast cells, but bradykinin, complement proteins, some interleukins, prostaglandins and TNF-alpha, may also trigger inflammation from other types of cells.
  • Circulating mast cells contain toll-like receptors, which can detect pathogen associated molecular patterns (PAMPS) on the surface of pathogens, and they will release an inflammatory mediator, such as histamine, in response.
  • Alternatively, mast cells may release inflammatory mediators due to signals from damaged cells (which will release clotting factors) during trauma or injury.
  • Other inflammatory mediators, such as TNF-alpha and IL-1 increase the expression of adhesion molecules on cells in the vascular endothelial cells.
  • The neutrophils loosely attach to the endothelial cells thorugh use of selectins, which is called rolling.

• Immunoassays for Disease

  • Immunology is the study of molecules, cells, and organs that make up the immune system.
  • When a foreign agent penetrates the first line of resistance, an immune reaction is elicited and immune cells are recruited into the site of infection to clear microorganisms and damaged cells by phagocytosis.
  • If the inflammation remains aggravated, antibody-mediated immune reaction is activated and different types of immune cells are engaged to resolve the disease.
  • The cellular component includes mast cells, neutrophils, macrophages, T and B lymphocytes, and plasma cells.
  • Because antibodies can be produced against any type of macromolecule, antibody-based techniques are useful in identifying molecules in solution or in cells.

• Pathogen Recognition

  • In addition to being released from cells after PAMP recognition, cytokines are released by the infected cells which bind to nearby uninfected cells, inducing those cells to release cytokines, resulting in a cytokine burst.
  • Interferons work by signaling neighboring uninfected cells to destroy RNA (often a very important biomolecule for viruses) and reduce protein synthesis; signaling neighboring infected cells to undergo apoptosis (programmed cell death); and activating immune cells.
  • A mast cell is a leukocyte that produces inflammatory molecules, such as histamine, in response to large pathogens.
  • A hypersensitive immune response to harmless antigens, such as in pollen, often involves the release of histamine by basophils and mast cells; this is why many anti-allergy medications are anti-histamines.
  • In response to a cut, mast cells secrete histamines that cause nearby capillaries to dilate.

• Development of Blood and Blood Vessels

  • New blood vessels are formed from endothelial stem cells, which give rise to the endothelial cells which line the vessels.
  • Endothelial stem cells (ESCs) are one of three types of stem cells found in bone marrow.
  • These parent stem cells, ESCs, give rise to endothelial progenitor cells (EPCs), which are intermediate stem cells that lose potency.
  • Progenitor stem cells are committed to differentiating along a particular cell developmental pathway.
  • Hematopoietic stem cells can of course undergo self-renewal, and are multipotent cells that give rise to erythrocytes (red blood cells), megakaryocytes/platelets, mast cells, T-lymphocytes, B-lymphocytes, dendritic cells, natural killer cells, monocyte/macrophage, and granulocytes.

• WBC Function

  • This process is performed primarily by mast cells, eosinophils, basophils, and NK cells.
  • This process is primarily performed by macrophages and dendritic cells.
  • Cell mediated activities.
  • This process is performed by T cells.
  • Memory cell activity.

• Cells and Organs of the Immune System

  • The thymus "educates" T cells and provides an inductive environment for the development of T cells from hematopoietic progenitor cells.
  • The innate leukocytes include the phagocytes, mast cells, eosinophils, basophils, and natural killer cells.
  • Mast cells reside in connective tissues and mucous membranes, and regulate the inflammatory response.
  • Natural killer cells are leukocytes that attack and destroy tumor cells, or cells that have been infected by viruses.
  • B cells and T cells are the major types of lymphocytes and are derived from hematopoietic stem cells in the bone marrow.