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This is a lecture on eosinophils,given by Tim Williams of Imperial College,
Eosinophils are granulocytes with
typically a bilobed nucleus andgranules 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, andthe 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 ingastrointestinal disorders, for
instance in eosinophilic eosophagitis.They're found in certain viral
infections and in certain tumors, forexample 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 andchallenge 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 theirsurfaces, 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.