Published on June 15, 2009 Reviewed on May 1, 2020   42 min

A selection of talks on Immunology & Inflammation

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This is a lecture on eosinophils, given by Tim Williams of Imperial College, London.
Eosinophils are granulocytes with typically a bilobed nucleus and granules that stain pink with eosin. They constitute normally about 1 to 4% of the white cells in the blood, and can be considerably higher in allergy and worm parasite infection. They're produced in the bone marrow, and the marrow contains precursors and a reserve of releasable mature cells. As well as in the blood, eosinophils also found normally in the GI tract.
Under disease conditions, eosinophils are found in response to helminth infection, in allergic asthma and also intrinsic asthma. They're found in the skin in allergic eczema, and they're also found in gastrointestinal disorders, for instance in eosinophilic eosophagitis. They're found in certain viral infections and in certain tumors, for example solid tumors of epithelial origin.
Individuals will asthma have high numbers of eosinophils in their lungs. If you take somebody who's sensitized to a particular allergen and challenge them with an aerosol of that allergen, you have an immediate reaction, bronchoconstriction reaction. And this is associated with the activation of mast cells via IgE fixed to their surfaces, and the release of mediators such as histamine and leukotrienes. After a delay off some two to four hours, you have a more protracted bronchoconstriction. And this is associated with the activation of T cells, Th2 lymphocytes, and the accumulation of high numbers of eosinophils.