2go METCHNIKOFF'S VIEWS ON OPSONINS 



absence of phagocytosis in vitro in the absence of serum he 

 attributes to a weakening and injury of the cells, due to the 

 method by which they are prepared, and admits that these 

 weakened and altered leucocytes will ingest bacteria more easily 

 and more quickly if the latter have previously been prepared by 

 the action of serum. He admits, however, that the opsonic index 

 determines the defensive resources of the blood, and in doing so 

 would appear to range himself definitely amongst the adherents 

 of the opsonin theory. But there is no reason to think that 

 washed leucocytes are weakened in respect of their phagocytic 

 powers ; they can take up enormous numbers of (opsonized) 

 bacteria in a very short space of time, and it is difficult to believe 

 that they could take up more in the living body ; and if, as there 

 is reason to think, phagocytosis is a physical process akin to 

 agglutination, the functional activity of the leucocytes is a factor 

 of little importance in phagocytosis, though essential for the 

 other, equally necessary, phenomena of digestion and solution 

 which take place subsequently. Metchnikoff finds that washed 

 bacteria can take up large numbers of bacteria slowly, even in 

 the absence of serum. This, however, proves nothing, since we 

 have seen there is some reason to believe that opsonin may be 

 formed from the leucocytes themselves. But, as a matter of fact, 

 the increase in phagocytosis in preparations incubated for one or 

 two hours as compared with those incubated for fifteen minutes 

 is slight as compared with that consequent on the addition of 

 serum. 



The influence of the source of the leucocytes taking part in 

 phagocytosis is not yet fully investigated, and there are no facts 

 known at present which tend to show that those from an immunized 

 animal have any special powers in this direction. Bulloch showed 

 in a few cases that leucocytes from different sources would take 

 up the same number of bacteria if used with the same opsonic 

 sera. There are also observations tending to show that diseased 

 or abnormal leucocytes e.g., those produced in excess as a result 

 of the injection of certain substances, such as nuclein are deficient 

 in phagocytic activity. 



In a very few cases some phenomena indicating an immunity, 

 and consequent increased phagocytic power of the leucocytes, 

 from an immune or infected person, as compared with the normal, 

 have been noticed. This, of course, is quite in accordance with 

 MetchnikofFs theoretical views. The examples are not numerous, 



