Endothelial Opsonins. 



171 



blood of the portal system, a large proportion of it becomes re- 

 tained in the liver provided alkali is simultaneously injected in 

 sufficient amount to produce a distinct lowering of the H-ion 

 concentration of the portal blood. A similar retention can not 

 be demonstrated by the above method when the dextrose solution 

 is neutral or, acid, or when it is made markedly hypertonic with 

 sodium chloride. 



94 («58) 



Endothelial opsonins. 



By W. H. Manwaring and Harry C. Coe. 



[From the Department of Bacteriology and Immunity, Leland Stan- 

 ford, Jr., University] 



If the blood-free liver of a normal rabbit is repeatedly perfused 

 with a sample of Ringer's solution containing a known number of 

 pneumococci, no diminution in the pneumococcic count of the 

 perfusion fluid is observed, even after a dozen passages through 

 the liver. 



If the liver of an actively immunized rabbit is similarly per- 

 fused, the pneumococcic count is rapidly decreased. After three 

 or four passages, the perfusion fluid usually becomes sterile. 



Histological study of the perfused liver now shows numerous 

 pneumococci adherent to the capillary endothelium. Few if any 

 agglutinated masses are seen. 



Normal rabbit serum added to the perfusion fluid in amounts 

 not exceeding 10 per cent, causes no appreciable retention of the 

 pneumococci by normal livers. Immune serum similarly added 

 causes a quantitive retention of the pneumoccoci. 



Immune serum will cause this retention when tested in less 

 than a hundredth of the concentration necessary to cause ag- 

 glutination. 



The serum component causing the pneumococcic retention is 

 thermo-stable (6o° C, 30 min.). 



Unagglutinated pneumococci sensitized by exposure to im- 

 mune serum and then washed free from serum, are retained 

 quantitatively by normal livers. 



The serum component responsible for the retention is therefore 



