SummaryPurified prethrombin was converted to thrombin in an activating system consisting of purified autoprothrombin C, purified Ac-globulin, lipid and calcium chloride. With the concentration of calcium and pH fixed, the effect of varying the other 3 pro-coagulants was studied.Conditions influencing the conversion of prethrombin to thrombin were determined. Autoprothrombin C is the enzyme, but with it alone activation was very slow. Best results were obtained with the simultaneous presence of autoprothrombin C, Ac-globulin and lipid. Reducing any one of the three toward zero concentration decreased the rate and yield of thrombin generation. In association with rapid thrombin generation Ac-globulin and autoprothrombin C were represented in approximately a 1:1 molar ratio. In that combination of Ac-globulin and autoprothrombin C the Michaelis constant for autoprothrombin C with prethrombin as a substrate was 3.14 × 10-6M.

SummaryThis report draws attention to the fact that only minute quantities of purified serum proteins (1 —15 μg/kg body weight) are required to stimulate antibody production. Injection of amounts greater than 1 mg/kg either is a waste or favors the production of non-specific antisera. Potent antisera can be produced in rabbits with a single intramuscular injection using either Al(OH)3 gel or Amphojel as an adjuvant.A number of purified plasma protein preparations which appear homogenous by ultra centrifugation or biological activity studies actually contain several antigenic components and are immunologically heterogeneous, when checked with highly specific antisera.Fibrinogen prepared by alcohol fractionation and tannic acid purification was found to be free of prothrombin, antihemophilic factor and Profibrinolysin. Both Immunoelectrophoresis and double diffusion in agar indicated a homogeneous preparation.Fibrinogens prepared from human, canine and bovine plasmas exhibited a low species specificity.