Mast cells -mast cells and basophils are the key cells in the development of anaphylactic shock, a type of hypersensitivity reaction. in this allergic response, a person who has been sensitized to a particular antigen on first exposure responds with release of secretions (heparin and histamine) from both mast cells and basophils, resulting in smooth muscle contraction (e.g., constriction of bronchioles), increased vascular permeability (dilation of blood vessels), and a reduction in blood pressure. in severe cases, circulatory or respiratory failure may occur. on an initial exposure to an antigen, ige binds to receptors on the mast cell and basophil surfaces. on second exposure, this bound ige functions as an antigen receptor. presence of antigen-antibody complexes on the cell surface induces release of secretion, including release of eosinophil-chemoattractant factor of anaphylaxis (ecf-a), histamine, heparin, and slow-reacting substance of anaphylaxis (srs-a). in the presence of allergens, allergy symptoms are induced by histamine and heparin, which increase vascular permeability and dilate blood vessels.
