GM-CSF Autoantibodies in Pulmonary Alveolar Proteinosis

To the Editor: Uchida et al. (Feb. 8 issue)¹ report that in patients with pulmonary alveolar proteinosis, neutrophil functions are impaired because of autoantibodies against granulocyte–macrophage colony-stimulating factor (GM-CSF). Although this may be true, neutralizing GM-CSF autoantibodies are found at high levels in a small proportion (<5%) of healthy persons. The Gammagard immune globulin used as a “negative” control by Uchida et al. contains these autoantibodies.^2,3 Pulmonary alveolar proteinosis has been described in patients without autoantibodies against GM-CSF,⁴ and pathological specimens from patients with this condition may respond to preparations of immunoglobulin containing these autoantibodies.⁵ When primed with 10 . . .