Which type of hypersensitivity is cytotoxic?

• A. Type II: Cytotoxic
• B. Type I: IgE-mediated
• C. Type III: Immune Complex-Mediated
• D. Type IV: Delayed hypersensitivity

Answer: (A)

Cytotoxic hypersensitivity is Type II. Here, antibodies (predominantly IgG or IgM) target antigens on the surface of cells or in the extracellular matrix. This binding activates complement or engages effector cells (like NK cells or phagocytes), leading to direct destruction or dysfunction of the targeted cells. That’s why it’s described as cytotoxic—the damage is caused directly to the cells bearing the antigen. Examples include autoimmune hemolytic anemia, transfusion reactions, Goodpasture syndrome, and myasthenia gravis, where antibodies against cell surface components or receptors trigger cell destruction or blockade.

In contrast, Type I is IgE-mediated and involves mast cell degranulation; Type III is driven by immune complex deposition in tissues; and Type IV is a T-cell–mediated delayed reaction.