Adding to the complexity of the type I reaction is the variety of cytokines released from mast cells and eosinophils. Some of these may contribute to the clinical manifestations of type I hypersensitivity. Human mast cells secrete IL-4, IL-5, IL-6, and TNF-a These cytokines alter the local microenvironment, eventually leading to the recruitment of inflammatory cells such as neutrophils and eosinophils. IL-4 increases IgE production by B cells. IL-5 is especially important in the recruitment and activation of eosinophils. The high concentrations of TNF-a secreted by mast cells may contribute to shock in systemic anaphylaxis. (This effect may parallel the role of TNF-a in bacterial septic shock and toxic-shock syndrome described in Chapter 12.)
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This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.