Allergies and Hypersensitivity Reactions

This chapter explores the various hypersensitivity reactions that can occur, which depend on the immune system's ability to recognize foreign antigens through the action of cellular receptors. It looks at the various types of hypersensitivity reactions and describes how these responses are identical to the ways in which the body reacts to foreign pathogens. It also reviews the four types of hypersensitivity reactions which differ based on the immune response: Type I, Type II, Type III, and Type IV. The chapter points out that Type I hypersensitivity reactions are driven by allergen recognition by IgE bound to granulocytes, while Type II hypersensitivity reactions are driven by the action of soluble immunoglobulins. Type III hypersensitivity reactions are caused by inefficient clearance of soluble antigens bound as small immune complexes in the bloodstream, while Type IV hypersensitivity is an induction of the cellular arm of the adaptive immune response.