Hypersensitivity and Autoimmunity · USMLE Step 1

A newborn develops hemolytic disease of the newborn due to maternal anti-Rh antibodies. Which hypersensitivity mechanism is responsible?

  1. IgE-mediated mast cell activation
  2. Antibody-mediated cytotoxicity
  3. Immune complex deposition
  4. Delayed-type T-cell reaction
Show answer and explanation

Correct answer: Antibody-mediated cytotoxicity

Type II hypersensitivity involves IgG-mediated cytotoxicity. Maternal IgG crosses the placenta and destroys fetal RBCs.

Difficulty: Medium Question 2 of 20

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