Type 1 hypersensitivity is an exaggerated immune response that occurs when the immune system overreacts to harmless substances, known as allergens, leading to the release of inflammatory mediators. This type of hypersensitivity is also known as immediate hypersensitivity because the reaction occurs rapidly after exposure to the allergen. It is the most common type of allergic reaction. Here's how Type 1 hypersensitivity occurs: 1. Sensitization: The first exposure to an allergen sensitizes the immune system. Antigen-presenting cells (APCs) process the allergen and present its fragments to helper T cells (Th2 cells) in the context of major histocompatibility complex II (MHC II) molecules. Th2 cells recognize the allergen as foreign and activate B cells to produce specific immunoglobulin E (IgE) antibodies against the allergen. 2. IgE Production: B cells, stimulated by Th2 cells, undergo class switching to produce IgE antibodies instead of the usual IgM or IgG antibodies. The...
