The Role of Laser Nephelometer in the Study of Abnormal Clotting Factors: Characterization of Two Abnormal Antithrombins (AT III Padua and AT III Padua2)

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Abstract
The immunologic concentration of two abnormal antithrombins III (AT III), namely antithrombin III Padua (AT III Padua) and antithrombin III Padua2 (AT III Padua2) and the kinetics of the reaction of these two ATs III with an anti AT III antiserum was investigated by means of a laser nephelometer. The immunologic concentration of these two AT III both in presence (0.2 IU/mL) or absence of heparin was normal. On the contrary, the analysis of kinetics behavior demonstrated that AT III Padua is radically different from pooled normal plasma both in presence or in absence of heparin. This was not the case for AT III Padua2, which showed no difference from pooled normal plasma regardless of the presence or absence of heparin. Both abnormal antithrombins III reached the plateau of the reaction at about the corresponding value of pooled normal plasma, indicating a normal antigen level. These experimental data were analyzed by means of a computer (Apple II 48 RAM) programmed to solve a four unknowns equation (Rodbard’s equation). This analysis showed that the time needed to reach half of the maximum voltage, i.e., the parameter C, which is expressed in minutes, is clearly longer in the case of AT III Padua samples (heparinized or not) as compared with pooled normal plasma. Moreover, the time at which the maximum rate was reached was also longer. On the contrary, in the case of AT III Padua2 there is no difference from pooled normal plasma. These data confirm the view that a different kind of defect is present in these two AT III abnormalities. Furthermore, they indicate that laser nephelometer may be a useful tool for the investigation of abnormal proteins.