In the Gell and Coombs framework, Graves disease is classified as type II hypersensitivity despite the absence of cell destruction. This unusual classification exists because:

• A Immune complexes deposit in thyroid capillaries and induce inflammation
• B Complement activation on thyrocytes releases preformed hormone
• C Cytotoxic T lymphocytes kill thyrocytes presenting thyroid antigen
• D The anti-TSH receptor antibody stimulates rather than inhibits its target cell ✓

Explanation

Type II reactions classically involve antibodies that opsonize cells or trigger complement-mediated lysis. Graves disease is included in this group because circulating IgG directed against the thyroid TSH receptor acts as an agonist, mimicking TSH signaling and driving unregulated hormone synthesis and secretion. It therefore represents antibody-mediated functional stimulation instead of destruction. Cytotoxic T cells and immune complexes (options C and A) belong to types IV and III respectively, and complement activation is not required for hormone release here.

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.