A 28-year-old man has had hemoptysis and hematuria for the past 2 days. On physical examination, his temperature is 36.8deg C, pulse is 87/min, respirations are 19/min, and blood pressure is 150/90 mm Hg. Laboratory studies show creatinine of 3.8 mg/dL and urea nitrogen of 35 mg/dL. Urinalysis shows 4+ hematuria, 2 + proteinuria, and no glucose. A renal biopsy specimen examined microscopically shows glomerular damage and linear immunofluorescence with labeled complement C3 and anti-IgG antibody. Which of the following autoantibodies has the greatest specificity for this patient's condition?

He has Goodpasture syndrome, in which an autoantibody is directed against type IV collagen in basement membranes of the glomeruli and in the lung. This is a form of type II hypersensitivity reaction. The antibodies attach to the basement membrane and fix complement, damaging the glomeruli. Anticardiolipin, along with anti-b2 -glycoprotein "lupus anticoagulant," are found with antiphospholipid syndrome, which may appear in systemic lupus erythematosus (SLE). These patients have coagulopathies with thrombosis or bleeding, or both. Anti-double-stranded DNA antibodies have specificity for SLE, whereas anti-histone antibodies are characteristic of drug-induced SLE. Anti-SS-A antibody is seen in Sjogren syndrome. The anti-Ul-ribonucleoprotein antibody is seen in mixed connective tissue disease (MCTD).