Urticaria, angioedema, and mediator release in humans in response to physical environmental stimuli

The activation of mast cells by immunologic or physical stimuli leads to the generation of unstored intermediates (mediators) such as slow reacting substance of anaphylaxis (SRS-A) and platelet activating factor (PAF), and to their release along with performed mediators, histamine, eosinophil chemotactic factor of anaphylaxis (ECF-A), and neutrophil chemotactic factor (NCE), and macromolecular heparin. The internal regulation of mast cell-dependent phenomenons occurs at at least four levels: 1) the intensity and nature of the activating stimulus, 2) the regulation of mediator generation and release of cellular levels of the cyclic nucleotides, 3) the capacity of target cells to bind and respond to primary mediators, and 4) the rate at which mediators undergo biodegradation. Inasmuch as the mast cell is present at cutaneous and mucosal surfaces about venules, it seems likely that the initial or humoral phase of its response achieves an influx of plasms proteins, such as immunoglobulins and complement components, whereas the subsequent cellular phase augments local host defense through the entrance of neutrophils and eosinophils that terminate the humoral phase. The activation of mast cells is considered herein in terms of defined physical stimuli that are characterized by urticaria and angioedema.