Mechanism for Goodpasture syndrome involves antibodies against which target?

• A. Type II hypersensitivity against the alpha-3 chains of type IV collagen.
• B. Type III hypersensitivity to basement membrane components.
• C. Type I hypersensitivity against glomerular mesangial cells.
• D. Immune complex mediated small vessel vasculitis.

Answer: (A)

Goodpasture syndrome is a cytotoxic antibody–mediated injury (type II hypersensitivity). Autoantibodies target the alpha-3 chain of type IV collagen in basement membranes, especially in glomeruli and alveoli. These basement membranes are common to both kidney and lung, so the autoimmune attack causes both rapidly progressive glomerulonephritis and pulmonary hemorrhage. The binding activates complement and brings in inflammatory cells, leading to tissue destruction of the basement membranes.

This isn’t an immune complex–mediated process (that would be type III) and it isn’t an IgE-driven allergic reaction (type I). The key point is the direct antibody binding to the alpha-3 chain of type IV collagen in basement membranes, producing cytotoxic damage.