Immunological Studies on Human Antithrombin III

Abstract

Immunoelectrophoresis of antithrombin III (At‐III) resulted in a single precipitation arc in the α 2 ‐region. At‐III was quantitated by electrophoresis or single radial diffusion in agarose gels containing antibodies. Addition of bovine thrombin apparently reduced the concentration of At‐III in serum by about 20%. Addition of At‐III antibodies to human serum or plasma reduced their progressive antithrombin activity by about 70% and abolished their heparin cofactor activity. The At‐III concentration in serum from healthy males decreases moderately with increasing age up to 60 years. In females below 45 years of age the concentration was significantly lower than in males. In females between 45 and 55 years a slight but significant increase was found bringing the concentration above that in males in the higher age groups. Use of oral contraceptives appeared to lower the At‐III concentration by about 15%.