322 INFECTION AND RESISTANCE 



but by that of blood cells as well. In spite of these points of likeness, 

 however, Neufeld 49 and his associates maintain rigidly that the two 

 substances are not the same and that the bacteriotropins are distinct 

 and independent antibodies. 



Among the reasons advanced in support of this opinion are the 

 facts that certain immune sera, both antibacterial and hemolytic, 

 may contain bacteriotropins without containing lysins and vice versa. 

 That this is undoubtedly true has been shown not only by Neufeld 

 and his associates but by Hektoen 50 and others, and it is likewise a 

 fact that in sera in which both functions are demonstrable they fre- 

 quently do not run quantitatively parallel. These are unquestionably 

 strong arguments, but their force is somewhat weakened, as Levaditi 

 has pointed out, by the fact that there are many varieties of bacterial 

 immune sera which undoubtedly sensitize the specific bacteria (as 

 can be shown by alexin fixation), but which do not lead to bacterio- 

 lysis. Wassermann 51 also attaches little value to the lack of parallel- 

 ism between the lytic and opsonic functions, expressing the belief 

 that the solubility of the particular antigen may determine whether 

 sensitization leads to phagocytosis or to lysis. With bacteria like 

 the cholera spirillum rapid lysis takes place, but when, as in pneumo- 

 cocci or streptococci, there is great resistance to lysis, sensitization 

 may lead to delayed lysis anticipated by leukocytic accumulation, 

 phagocytosis, and intracellular digestion. 



It by no means follows from mere lack of parallelism, therefore, 

 that the two serum functions are dependent upon separate antibodies,, 

 although the argument is sufficiently strong to impose conservatism 

 in identifying them. 



Another important argument advanced against the identification 

 of bacteriotropins with the bactericidal sensitizers or amboceptors is 

 the fact that the former lead to phagocytosis without the participa- 

 tion of alexin, whereas the latter become active for lysis only when 

 alexin is present. 



This point also has constituted Neufeld's strongest support for 

 maintaining that the bacteriotropins or immune opsonins are entirely 

 distinct from the normal opsonins. It is true, indeed, that immune 

 serum, unlike normal serum, may opsonize powerfully even after 

 heating to temperatures which destroy alexin. 



If we regard the heat-stable lytic antibody as an amboceptor in 

 the strict sense of Ehrlich, as a specific "Zwischenkorper" with a 

 complementophile group, this argument would have considerable 

 weight. Even in this case, however, strong sensitization of the bac- 

 teria may make them amenable to the living cells the phagocytes - 



49 Neufeld and Topfer. Centralbl. f. Bakt., 1, 38, 1905. 



50 Hektoen. Jour, of Inf. Dis., 6, 1909. 



51 Wassermann. Deutsche med. Woch., Vol. 33, No. 47, 1907. 



