AGGRESSINS 125 



the body-cells, although they may be produced artificially in the test- 

 tube with large numbers of bacteria and a non-poisonous agent (serum 

 or distilled water) which can disintegrate the cells. In this manner 

 Wassermann and Citron have produced "artificial aggressins, " which act 

 in the same general manner as the "natural aggressins" of Bail. 



By many the aggressins are regarded as endotoxins, and while they 

 may possess the nature of endotoxic substances, it is to be remembered 

 that there is no definite relation between the poisonous qualities of the 

 aggressins and their power to increase the virulence of an infection. It 

 is probable, as has been shown by Wassermann and Citron, that patho- 

 genic bacteria contain small amounts of natural aggressin. This ag- 

 gressin may be regarded as a normal antibody of the bacterium against 

 the defensive forces of the body-cells of a host. During infection these 

 aggressins or antibodies are naturally greatly increased, as the bacteria 

 require more and more protection. Being contained to some extent 

 within the bacterial cells, the antibodies are somewhat similar to endo- 

 toxins : while endotoxins may be regarded as offensive agents of bacte- 

 ria, aggressins may be their defensive agents. This belief is in keeping 

 with the hypothesis of Welch 1 and also of Walker 2 , according to which 

 it may be presumed that bacteria, as living cells, when so placed that 

 they are exposed to the defensive forces of their host, are, under favor- 

 able conditions stimulated to produce reciprocal antibodies for their 

 protection, and to generate them in increasing amounts as may be neces- 

 sary. I regard aggressins as antibodies of this nature, and consider 

 that they are produced according to the conditions laid down in Pro- 

 fessor Welch's hypothesis. 



Bail regards the aggressins as new substances; as already stated others 

 regard them as simple endotoxins; still others believe them to be free 

 bacterial receptors, and that these receptors may combine with bacterio- 

 lytic amboceptors, producing, as it were, a deflection of the amboceptors, 

 so that the bacteria themselves are not attacked, and thus continue to 

 proliferate. The action of aggressins is not dependent upon the toxicity 

 of the endotoxins, for the fluid containing them is devoid of toxic effects; 

 at most, therefore, if they are of the nature of receptors, they possess no 

 toxophorous portion. 



Whatever aggressins may be, and we regard them as antibodies of 

 bacteria, just as bacteriolysins are antibodies of tissue-cells, they appear 

 to be especially directed against opsonins, neutralizing these, paralyzing 

 leukocytes, and thus inhibiting or entirely preventing phagocytosis, 

 it. Med. Jour., 1902, 2, 1105. 2 Jour. of Path., 1902, 8, 34. 



