ANTI-ENZYME IMMUNITY 271 



2. Postulates on the Role of the Bacterial Fibrinolytic 

 Factor 



Garner and Tillett (1934a) obtained a preparation of fibrinolytic 

 factor from broth filtrate of streptococcal culture by precipitating with 

 three volumes of alcohol, or by adsorption on alumina and elution by 

 phosphate buffer. The preparation was relatively heat resistant, and 

 stable in the dry form for over a year's period. The optimal temperature 

 of activity was within the range of35°to45°C., and the optimal pH 

 of activity was 7.3. The activity of the factor was rapidly destroyed 

 by trypsin and by papain. The factor was incapable of digesting casein, 

 gelatin or peptone. They claimed that they had recovered bacterial 

 factor from a reaction mixture which had undergone lysis and then 

 demonstrated its activity on a new sample of fibrin. There is no infor- 

 mation concerning the question whether or not the recovered sample 

 contained the active serum-frotease. This protease, if 'present, could 

 have heen responsible for the lysis of the new sample of fihrin. In the 

 absence of specific information concerning this question the original 

 claim of Garner and Tillett (1934a) (based on this experiment) that 

 bacterial fibrinolytic factor behaves like an enzyme requires verifica- 

 tion. 



Christensen (1945, 1946) using a partially purified fibrinolytic 

 factor, found that his preparation was only slowly destroyed by heating 

 at 100°C. at pH 7.4. It was readily destroyed by treatment with trypsin 

 and pepsin, indicating that the activity was associated with a protein. 

 This factor per se lacking proteolytic activity when added to protein 

 solutions as substrates, raises the question as to how it exercises its 

 effect on the lysis of a fibrin clot. Milstone (1941) had made the im- 

 portant observation that human serum and plasma contains a "lytic 

 factor" which is essential for the lysis of fibrin by streptococcal fibrino- 

 lytic factor. If fibrin is free from traces of serum or plasma, the strepto- 

 coccal factor has no effect on fibrin clot. Such fibrin was rendered sus- 

 ceptible to the action of streptococcal factor, however, by the addition 

 of "lytic factor" present in the euglobulin fraction of normal human 

 serum. Rabbit fibrin which has been reported to be insensitive to the 

 action of the streptococcal factor, likewise was dissolved when treated 

 with human "lytic factor." 



