A 28-year-old woman with Graves disease has autoantibodies that stimulate the TSH receptor on thyroid follicular cells, causing hyperthyroidism. This mechanism is classified as which type of hypersensitivity reaction?

• A Type I hypersensitivity (IgE-mediated mast cell degranulation)
• B Type II hypersensitivity (antibody-mediated cellular stimulation) ✓
• C Type III hypersensitivity (immune complex deposition)
• D Type IV hypersensitivity (T-cell mediated cytotoxicity)

Explanation

Graves disease is a Type II hypersensitivity reaction where IgG autoantibodies bind the TSH receptor and stimulate it rather than block it. This is antibody-mediated cellular stimulation, distinct from complement-mediated lysis seen in hemolytic anemia or receptor blockade in myasthenia gravis. Type III involves immune complex deposition, and Type IV requires sensitized T cells.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.