They also play a role in resistance to virus infections. The lysis of infected cells leads, in due course, to the elimination of the infection. It is believed that many tumor-associated antigens may also be similarly presented on the cell surface, and CTLs are therefore also involved in tumor immunity.
Much has been learned about the mechanisms by which CTLs kill their targets, and this knowledge may be of value in therapeutic modulation of T cell-mediated cytotoxicity in the settings of some autoimmune diseases. Two principal mechanisms of T cell-mediated damage have been discovered: 1 perforin-granzyme-dependent killing, and 2 Fas-Fas ligand-dependent killing.
Perforins and granzymes are preformed mediators contained in the lysosome-like granules of CTLs. The CTL granules contain proteases called granzymes, which are delivered into the target cells via the perforin-induced pores.
Once within the cell, granzymes activate caspases, which induce apoptosis of the target cells. In addition, the perforin pores allow water to enter the cells, thus causing osmotic lysis. Fas-dependent killing also induces apoptosis of the target cells but by a different mechanism.
This interaction leads to apoptosis. Molecular pathology B. Cellular pathology C. Tissular pathology D. General pathology E. Pathology by systems F. Pathology by regions G. Tumoral pathology H. Case records K. Info - Admin Resources in pathology Technical section. Delayed Type Hypersensitivity The classic example of delayed hypersensitivity is the tuberculin reaction, which is produced by the intracutaneous injection of tuberculin, a protein-lipo polysaccharide component of the tubercle bacillus.
Type IV hypersensitivity reactions e. Unlike true hypersensitivity reactions, which occur after sensitization , nonallergic hypersensitivity reactions e.
Type IV : delayed T-cell mediated. Drugs can cause all four types of hypersensitivity reactions. Type I is Fast and Furious. Contact prevention and avoidance of offending agents is the best treatment for allergies.
IgM and IgG mistakenly bind to surface antigens of the cells in the body , which results in:. Type II is cytoxic and consists of 2 components antigen and antibody.
Type IV hypersensitivity reactions involve two major steps:. Contact dermatitis due to poison oak , poison ivy , or poison sumac is the most likely cause in a patient presenting with itching, burning, red skin lesions arranged in a linear pattern appearing 24 hours after a camping trip. Expand all sections Register Log in. Trusted medical expertise in seconds. Find answers fast with the high-powered search feature and clinical tools.
Try free for 5 days Evidence-based content, created and peer-reviewed by physicians. Read the disclaimer. Hypersensitivity reactions. Summary Hypersensitivity reactions occur when the normally protective immune system responds abnormally, potentially harming the body.
Hypersensitivity classification [1] [2] Summary of pathophysiology Examples Type I : immediate Preformed IgE antibodies coating mast cells and basophils are crosslinked by contact with free antigen. Cell degranulatio n results in the release of histamine and other inflammatory mediators. The normal immune system is a complex system that protects our bodies from infections. Our skin, lungs and gut have cells that help to protect us.
There are also many other cells of the immune system that are called to action if we become infected with a bacteria, virus or parasite. Two important types of immune system cells are types of white blood cells, or lymphocytes.
These are called to action by signals in the immune system that let them know a foreign invader is present. B cells, so-called because they develop in bone marrow recognize certain types of foreign cells and produce antibodies. Multiple sclerosis is considered to be an immune-mediated disease in which the body's immune system attacks the central nervous system CNS.
Most MS experts believe it to be an autoimmune disease, although no specific antigens proteins that stimulate the immune system have been identified in MS. Some diseases thought to have an autoimmune basis are:. In the case of MS, the immune system attacks and damages certain structures and cells within the CNS, including:.
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