Immunological aspects and inflammatory mechanisms of allergic reactions

The tissue changes and symptoms that occur during an allergic reaction in the upper respiratory tract are due to inflammatory reactions. The authors give a survey of the different allergic reactions and discuss the different components of the IgE mediated hypersensitivity which is the most important type of hypersensitivity in the upper airways. The production of IgE, the immunoglobulin of the immediate hypersensitivity reaction, is modulated by T-cells through the activity of cytokines. Antigen presenting cells, including Langerhans cells, play an important role in the sensitisation phase. Mast cells and basophils degranulate as a result of a complex enzymatic pathway, in which phosphatidylinositol plays an important role. The mediators released by these cells include vasoactive substances, chemotactic agents and inflammatory proteases; these mediators and those liberated by secondary recruited cells, such as eosinophils and basophils will be responsible for the early and late symptoms.