Inter-alpha-trypsin inhibitor and pre-alpha-trypsin inhibitor in health and disease. Determination by immunoelectrophoresis and immunoblotting.

Inter-alpha-trypsin inhibitor (ITI) consists of 3 polypeptides cross-linked by chondroitin sulphate, which is o-glycosidically linked to the smallest of the polypeptides, designated bikunin. Pre-alpha-trypsin inhibitor (p alpha I) consists of bikunin and a fourth polypeptide, also associated by chondroitin sulphate. Crossed immunoelectrophoresis (CIE) of plasma, using immunoglobulins to ITI, revealed 3 precipitation-lines, two of which increased in size during disease. Molecular mass determination by polyacrylamide gel electrophoresis showed that the immunoprecipitates contained mixtures of proteins. Therefore CIE is unfit for quantitation of the individual proteins related to ITI. Immunoblotting suggested that the plasma concentrations of p alpha I and of bikunin was increased in uraemia, rheumatoid arthritis and after trauma. The plasma concentrations of ITI and of p alpha I were decreased in a patient with endocarditis.