Serum levels of a component reacting with antiserum to urinary antitrypsin in health and disease with emphasis on high levels in renal failure.

A component in serum reacting immunologically to form a precipitate with an antiserum to purified urinary trypsin inhibitor (CRAUTI) was measured by radial immunodiffusion. CRAUTI was demonstrated in the sera of 94 normal subjects and 350 patients with a variety of illnesses. With few exceptions it was increased only in patients with renal disease. The amount of CRAUTI increased as glomerular filtration rate decreased and returned to normal promptly after successful renal transplantation. CRAUTI was nondialyzable. CRAUTI is immunologically related to but not identical with inter-alpha-trypsin inhibitor.