All are type-II hypersensitivity reaction except-
**Core Concept**
Type-II hypersensitivity reactions involve the binding of antibodies to cell surface antigens, leading to cell destruction through mechanisms like complement activation and antibody-dependent cellular cytotoxicity. These reactions typically occur against cellular or tissue antigens, often resulting in damage to specific tissues or organs.
**Why the Correct Answer is Right**
Type-II hypersensitivity reactions are characterized by the presence of antibodies directed against cell surface antigens, such as in autoimmune hemolytic anemia or Goodpasture's syndrome. The antibodies can activate the complement system, leading to cell lysis, or recruit immune effector cells, like natural killer cells or neutrophils, to destroy the targeted cells.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because, although it is a type of hypersensitivity reaction, it is not type-II. Type-IV hypersensitivity reactions are cell-mediated and involve T-cell activation, as seen in contact dermatitis or tuberculosis.
**Option B:** This option is incorrect because, like the correct answer, it is a type of hypersensitivity reaction. Type-IV hypersensitivity reactions are cell-mediated and involve T-cell activation, as seen in contact dermatitis or tuberculosis.
**Option C:** This option is incorrect because, like the correct answer, it is a type of hypersensitivity reaction. Type-IV hypersensitivity reactions are cell-mediated and involve T-cell activation, as seen in contact dermatitis or tuberculosis.
**Clinical Pearl / High-Yield Fact**
It is essential to remember that type-II hypersensitivity reactions are typically mediated by IgG or IgM antibodies, which can activate the complement system and lead to cell destruction.
**Correct Answer: D.**