IMMUNOELECTROPHORETIC QUANTITATION OF ANTITHROMBIN III:

Comparison of immunochemical and biological properties of human anti thrombin during blood clotting and upon interaction with exogenous thrombin

Modification of immunological and biological properties of human antithrombin were studied in plasma-serum pairs and in defibrinated plasma supplemented with human thrombin. Modified antithrombin obtained through whole-blood clotting or upon addition of exogenous thrombin appeared the same with regards to its electrophoretic or biological properties. However, amounts of thrombin higher than that physiologically available, had to be used to obtain a "serum-like" antithrombin in thrombin supplemented plasma suggesting different pathways for this transformation. This was in agreement with the observation in plasma of a modification of antithrombin antigenic properties upon thrombin addition whereas no difference was demonstrated when comparing serum to normal plasma. It may be concluded that the inactivation of antithrombin and the appearance of electrophoretically modified forms in normal serum is not mainly due to the formation of enzyme-inhibitor complexes and therefore that proteolytically modified, enzyme-free forms of antithrombin demonstrated in purified systems (Fish et al. 1979) could be of physiological relevance.

Practical requirements for immunochemical analysis of antithrombin III in agarose gels

This report emphasizes the importance charged groups affixed to the agarose gel matrix have on immunoprecipitation of antithrombin III (AT) and of its protease complexes. Plasma and serum samples were analyzed for antithrombin III by electroimmunoassay and single radial immunodiffusion in different types of agarose. The results were compared with the amount of functionally active AT contained in the samples. A high correlation between the results was obtained provided the following criteria were fulfilled: (1) agarose with a sulphate content of 0.2% or more was used; (2) the antiserum should contain antibodies directed to AT plus antigenic determinant(s) that emerge(s) during the AT-protease interaction; (3) a gel buffer of about 75 mmol/l was used. Heparin added to the test system competed with sulphate groups affixed to the agarose gel matrix and inhibited immunoprecipitation of AT.

Development of large scale fractionation methods. VII. Preparation of antithrombin III concentrate

A large scale method for preparation of antithrombin III (AT III) concentrate from plasma or from Cohn fraction IV-1 (Fr. IV-1) has been described. It consists of the following steps: (a) partial purification by precipitation of impurities with 20% polyethylene glycol (PEG) 4000; (b) isolation of AT III from the PEG supernatant by batch adsorption and elution on heparin-Sepharose at a ratio corresponding to 45 vol of plasma or 80 vol of 10% Fr. IV-1 solution to 1 vol of gel; (c) concentration and desalting of the eluted AT III on a Pellicon ultrafiltration system; (d) pasteurization of AT III concentrate by heating for 10 h at 60 degrees C in the presence of 0.5 M sodium citrate at pH 7.5; (e) removal of excess citrate by gel filtration on Sephadex G-50; and (f) sterile filtration, filling and lyophilization. The recovery by activity was 32% from a 113-liter plasma batch and 16% from a 42-kg Fr. IV-1 batch. Both AT III concentrates, derived either from plasma or from Fr. IV-1, had similar specific activity and electrophoretic purity, were nonpyrogenic and met all other FDA requirements for biologic products. Pasteurization induced changes in disc gel and isotachophoretic patterns of AT III preparations.