| • | unlike histiocytes, eosinophils, lymphocytes, and neutrophils, all of which are bone marrow derived, arise from undifferentiated mesenchymal cells |
| • | IgE mast cell degranulation results in release of 2 categories of mediators: |
| 1. | preformed chemicals stored in mast cells (and basophils) |
| • | eosinophil chemotactic factor of anaphylaxis (ECF-A) |
| • | neutrophil chemotactic factor of anaphylaxis (NCF-A) |
| 2. | newly formed chemicals generated immediately within mast cells (and basophils) |
| • | slow reacting substance of anaphylaxis (SRS-A): like histamine, increases vascular permeability, but is unaffected by antihistamines |
| • | platelet aggregating factor |
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