Type I hypersensitivity is

Type I hypersensitivity is

• A. Associated with complement-mediated cell lysis
• B. Due to immune complex deposition
• C. Mediated by activated macrophages
• D. An immediate allergic reaction

Answer: (D)

Type I hypersensitivity is driven by IgE antibodies bound to mast cells and basophils; when an allergen cross-links these IgE molecules, it triggers rapid degranulation and release of histamine and other mediators, producing a quick, immediate allergic reaction with symptoms like itching, redness, swelling, bronchoconstriction, and increased secretions. This contrasts with other hypersensitivity types: not due to immune complex deposition typical of Type III, not primarily from complement-mediated cell lysis seen in Type II, and not driven by macrophage-mediated processes that underlie many Type IV delayed reactions.

Type I hypersensitivity is driven by IgE antibodies bound to mast cells and basophils; when an allergen cross-links these IgE molecules, it triggers rapid degranulation and release of histamine and other mediators, producing a quick, immediate allergic reaction with symptoms like itching, redness, swelling, bronchoconstriction, and increased secretions. This contrasts with other hypersensitivity types: not due to immune complex deposition typical of Type III, not primarily from complement-mediated cell lysis seen in Type II, and not driven by macrophage-mediated processes that underlie many Type IV delayed reactions.