title: Heparin cofactor activities in a family with hereditary antithrombin III deficiency: evidence for a second heparin cofactor in human plasma.
abstract: Plasma levels of antithrombin-heparin cofactor, determined by heparin-dependent antithrombin assay, and antithrombin III antigen were measured in 22 members of a large kindred predisposed to venous thrombosis. While 11 members had reduced plasma levels of both antithrombin-heparin cofactor and antithrombin III antigen, the levels of antithrombin-heparin cofactor were always greater than the levels of antithrombin III antigen: 66% (+/- 7%) and 49% (+/- 5%) of normal plasma, respectively. Pooled normal plasma and plasma from one of the affected family members (60% antithrombin-heparin cofactor and 47% antithrombin III antigen) were fractionated by heparin-agarose affinity chromatography. Antithrombin-heparin cofactor, which eluted from heparin-agarose with buffer containing 0.4 M NaCl and did not cross-react with antibody specific for antithrombin III and did not inhibit factor Xa at an appreciable rate in the presence of heparin, was designated heparin cofactor A. Antithrombin-heparin cofactor, which eluted from heparin-agarose with buffer containing 2.0 M NaCl, was functionally and antigenically identified as antithrombin III. The concentrations of heparin cofactor A in normal and patient plasma were similar (4.5 x 10(-7) M), while the concentration of antithrombin III in patient plasma (8.0 x 10(-7) M) was only 50% of normal (1.6 x 10(-6) M). The functional properties of both heparin cofactor A and antithrombin III obtained from patient plasma were normal. From the results of the present study it would appear that the antithrombin-heparin cofactor concentrating measured in patient plasma reflects the combined concentrations of heparin cofactor A and antithrombin III. Since heparin cofactor A does not cross-react with antibody to antithrombin III, the concentration of antithrombin III antigen in patient plasma is thus lower than the concentration of antithrombin-heparin cofactor.
mesh_terms: D000990:Antithrombin III / Q000097:blood / Q000276:immunology; D020152:Antithrombin III Deficiency; D003374:Coumarins / Q000627:therapeutic use; D000939:Epitopes / Q000032:analysis; D006801:Humans; D008297:Male; D008875:Middle Aged; D010375:Pedigree; D011655:Pulmonary Embolism / Q000188:drug therapy / Q000209:etiology; D013924:Thrombophlebitis / Q000097:blood / Q000150:complications / Q000235:genetics*
chemical_list: D003374:Coumarins; D000939:Epitopes; D000990:Antithrombin III