Antithrombin III microheterogeneity in antithrombin III deficiency and in the antithrombin III abnormality,...

Antithrombin III (AT III) microheterogeneity was investigated in 12 cases of congenital AT III deficiency and 2 cases of congenital AT III abnormality by isoelectric focusing (IEF) and immunofixation. In congenital AT III deficiency, IEF and immunofixation revealed AT III as 8 bands which was indistinguishable from normal control in terms of the number of bands and the isoelectric point (pI) of each band. In the proband of the congenital AT III abnormality, however, IEF and immunofixation showed AT III as 8 bands which shifted slightly but definitely to the acidic side compared to those of normal subjects. This change in pI of the abnormal AT III was considered to reflect the amino acid replacement in the polypeptide chain of the abnormal AT III molecule.