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  #1  
Old 10-27-2009
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Immunology Why eosinophils involved in hypersensitivity reaction?

Regarding type 1 hypersensitivity, from what I read in First Aid pg 202, it says that IgE cross-links mast cells and basophils, causing release of vasoactive amines.

Now my question is, there is eosinophillia in type 1 hypersensitivity right? Why is it eosinophilia? How is eosinophil involved in this type 1 hypersensitivity? I thought it is more for the anti-parasite?
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Old 10-27-2009
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Default Type I hypersensitivity and Eosinophils

Early phase mediators are released from mast cells and basophils. One of these mediators is called the Eosinophil chemotactic factor A which will attract eosinophils into the area.
Eosinophils will then release the late phase mediators such as PGE2 and Leukotrienes. Late phase response is much more powerful than the early phase.
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Ohh, that makes sense. THanks.
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Old 10-27-2009
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actually the answer is in histology.
mast cells and basophils...and granulocytes....so they granulate in response to FC portions of antibodies cross linkages.
The granules secreate excessive amounts of the inflammotory promoter HISTAMINE...
SO...there has to be something to deactivate the HISTAMNE....
HISTAMINASES are present in the granules of EIOSINOPHIlic granules.
hence in Allergy, and hypersensitvity...eiosinophils are active to counteract and limit the inflamation, in this case.so eiosinophil s persist in such patients even if they are no in active allery or asthma...etc...
you can check this in whethers, the atlas...they have cool micrographs...
let me know if youre not clear...
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Old 05-21-2011
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great explanation quratulain, spoken like an excellent pathologist
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Old 05-22-2011
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wt ive learnt from goljan patho
after first xposure there is stimulation of Th2 cells tht secrete leukotrienes.
of them IL 5 stimulates proliferation n maturation of eosinophils tht then secrete major basic proteins for activation of mast cells, chemotactic factor A n also enzyme peroxidase tht generates O2 radicals n kill the target cells
so! u c eosinophilia in allergy due to IL5))))))
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Old 11-18-2012
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Smile IL 5 released by CD 4 cells

Quote:
Originally Posted by lemontea88 View Post
Regarding type 1 hypersensitivity, from what I read in First Aid pg 202, it says that IgE cross-links mast cells and basophils, causing release of vasoactive amines.

Now my question is, there is eosinophillia in type 1 hypersensitivity right? Why is it eosinophilia? How is eosinophil involved in this type 1 hypersensitivity? I thought it is more for the anti-parasite?
Allergens are processed by APCs and they are presented to Cd4 cells by MHC class 2 receptors, in response CD 4 cells release IL 4 and IL 5, this IL 5 stimulates eosinophils.
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Old 08-19-2014
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Default Update

Good post, but apparently the theory has been updated now

Eosinophils (attracted by ECF-A in mast cell granules) are now believed to OVERALL increase and maintainthe inflammatory response. That's why you would still warrant corticosteroid use.

Because Eosinophils release competing factors:
1) arylsulfatase and histaminase - decrease inflammation by breakdown of inflamm factors e.g. histamine (as quratulain helpfully mentioned, and still a good mnemonic imo).
2) LTC4 and PAF - stim mast cells to release more cytokines - this wins out.

Quote:
Originally Posted by quratulain View Post
actually the answer is in histology.
mast cells and basophils...and granulocytes....so they granulate in response to FC portions of antibodies cross linkages.
The granules secreate excessive amounts of the inflammotory promoter HISTAMINE...
SO...there has to be something to deactivate the HISTAMNE....
HISTAMINASES are present in the granules of EIOSINOPHIlic granules.
hence in Allergy, and hypersensitvity...eiosinophils are active to counteract and limit the inflamation, in this case.so eiosinophil s persist in such patients even if they are no in active allery or asthma...etc...
you can check this in whethers, the atlas...they have cool micrographs...
let me know if youre not clear...
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Old 08-19-2014
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Yes that's true! Histamine, Heparin and Eosinophil Chemotactic Factor A (ECFA) are released quickly because they are preformed substances, hence dubbed "early phase mediators". ECFA, recruits eosinophils, and they normally release cationic granule proteins like major basic proteins and eosinophil cationic proteins that kill parasites and host cells, but they also release enzymes like peroxidase that cause tissue remodeling.

Also, after sensitization the IgE antibodies are attached to the Fc portion of the mast and basophil cells. They only DEGRANULATE, when the allergens bind to the idiotypes of IgE antibodies!
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