Posted: 08.09.2011 at 03:29:31
A terrific resource:
J Allergy Clin Immunol. 2010 February; 125(2 Suppl 2): S73–S80.
from that article about Ige, Mast Cells, Basophils and Eosinophils:
Mast cell activation through FcεR1 is central to the pathogenesis of allergic diseases, including anaphylaxis, allergic rhinitis, and allergic asthma. Activation of FcεR1 by polyvalent allergen recognized by bound IgE leads to the initiation of an immediate hypersensitivity reaction, as well as a late-phase reaction. The immediate reaction is determined by pre-formed mediators and rapidly synthesized lipid mediators and results in: erythema, edema, and itching in the skin; sneezing and rhinorrhea in the upper respiratory tract; cough, bronchospasm, edema, and mucous secretion in the lower respiratory tract; nausea, vomiting, diarrhea, and cramping in the gastrointestinal tract; and hypotension. Late phase reactions are mediated by cytokines and chemokines and can occur 6–24 hours after the immediate reaction. Late phase reactions are characterized by edema and leukocytic influx and may play a role in persistent asthma.
This is why, characteristically, biphasic
reactions occur to begin with-- and why they tend to differ markedly from initial phase reactions in terms of clinical features. They resist
treatment because most of the treatment for allergic reactions is about those 'released' mediators (not the 'synthesized' ones that are more dominant in late-phase reactions).
The entire article, while technically challenging for the lay reader, is WELL WORTH THE EFFORT. It goes a long way toward explaining why the signalling pathways that produce anaphylaxis are so difficult to shut down. For one thing, there are a LOT of them, there are a tremendous variety of mediators released (all possessing unique physiological signalling of their own), and many of the individual pathways contain feedback loops that amplify responses once activation occurs.
<sigh> But I'm still looking for my figure that shows the activation of the system by an allergen docking with IgE.
"To travel hopefully is a better thing than to arrive." -Robert Louis Stevenson