OPSONIC ACTION 577 



whose liver cells were used. These are mentioned as examples of a very 

 large group of specific activities. 



With regard to the sites of origin of immune-bodies our 

 information is still very deficient. Pfeiffer and Marx brought 

 forward evidence in the case of typhoid, and Wassermann in the 

 case of cholera, that the immune-bodies are chiefly formed in 

 the spleen, lymphatic glands, and bone-marrow. According to 

 certain workers of the French school, the chief source of anti- 

 substances acting on cells such as red blood corpuscles is the 

 large mononuclear leucocytes, whilst those acting on bacteria 

 are chiefly derived from the polymorpho-nuclear leucocytes (vide 

 p. 589). Another view is that immune-bodies are chiefly formed 

 by the large mononuclear leucocytes, whilst complements are 

 products of the polymorphs. That these cells are concerned in 

 the production of antagonistic and protective substances is almost 

 certain, though another possible source of wide extent, namely, 

 the endothelium of the vascular system, has been largely over- 

 looked. As yet, definite statements cannot be made on this 

 point. 



(b) Opsonic Action. — The presence of a substance in an 

 immune-serum which makes the corresponding organism sensi- 

 tive to phagocytosis was first demonstrated by Denys and Leclef 

 in 1895, in the case of an anti-streptococcal serum. They also 

 showed that the serum produced this effect by acting on the 

 organism, not on the leucocytes. It is, however, chiefly to the 

 researches of Wright and his co-workers that this subject has 

 come into special prominence. Wright and Douglas in their 

 first paper showed that the phagocytosis of staphylococci by 

 leucocytes depended on a body in the normal serum which 

 became fixed to the cocci and made them a prey to the 

 phagocytes. To this they gave the name of "opsonin" (vide 

 p. 120). There is no phagocytosis of cocci by leucocytes 

 washed in salt solution ; normal serum heated to 55° C. is also 

 without effect in inducing this phenomenon. They could not 

 demonstrate any effect of the opsonin on the leucocytes. On the 

 other hand, if bacteria be exposed to the fresh serum, and they 

 be freed from the excess of serum and then exposed to leuco- 

 cytes, also washed free from serum, they will be readily taken 

 up by the cells. It has been shown that the opsonic action 

 of the serum against an organism is increased by the process of 

 immunisation, and the opsonic index represents the degree of 

 immunity in one of its aspects as already explained (p. 122). 

 The matter has, however, become complicated by the fact that 

 in an immune-serum an opsonin may still be present after the 



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