105 



CAN OPSONINS BE OBTAINED DIRKCTLY FROM 



BACTERIA AND YEASTS 1 



By R. Greig-Smith, D.Sc, Maclbay Bacteriologist to the 



Society. 



The curve of the opsonic indices of an individual who has been 

 treated with a bacterial vaccine, shows soon after inoculation a 

 fall and a subsequent rise, after which the curve remains at a 

 level higher than it had before the inoculation. The falling and 

 rising have been called by Wright the negative and positive 

 phases. It is reasonable to suppose that the injected microbe 

 gives out a substance, either an anti-opsonin or an anti- 

 phagin, which is responsible for the negative phase. We 

 know that saline does extract such a substance from bacteria.* 

 But it is not known if, subsequent to the liberation of all the 

 anti-phagin, the bacteria give off the opsonin which produces the 

 positive phase. From what we believe to be the mechanism of 

 immunisation, it is probable that the opsonin is not derived 

 directly from the bacteria but rather from the body-cells in 

 response to the anti-phagin. On the other hand we know that 

 the ingestion of yeast, from which I have not been able ta 

 obtain evidence of the secretion of an anti-opsonin, leads to the 

 production of a certain amount of immunity against staphylo- 

 coccus. The digestion of the yeast would therefore appear to 

 give rise to opsonin, and such being the case, it is difficult to 

 think otherwise than that the digestion of the bacteria would 

 bring about the same result. We know that bacteria and yeast 

 are comparatively rich in nucleoproteid, and we have it from 

 Busse that nucleic acid protects the individual against the 

 invasion of staphylococci and B. coli. 



*These Proceedings, 1908, p. 669. As the anti-body is not destroyed at 

 70° it is not aggressin. 



