258 INFLAMMATION 



Influence of the Serum on Phagocytosis (Opsonins). — Phagocytosis of bac- 

 teria by leucocytes seems not to be merely a reaction between the leucocytes and 

 the bacteria. Wright and Douglas have demonstrated that certain substances 

 in the blood-serum are necessary to prepare the bacteria for phagocytosis, these 

 substances being termed by them "opsonins." If leucocytes are washed free 

 from serum with salt solution and let stand in a test-tube with such bacteria as 

 Streptococcus pyogenes, Staphylococcus pyogenes, B. typhosus, B. coli, B. tuberculosis, 

 and various other organisms, no phagocytosis occurs. If, however, some serum 

 from a normal or an immunized animal is added to the mixture, active phago- 

 cytosis soon takes place. The action of opsonins is also involved in phagocytosis 

 by endothelium." The character and properties of the opsonins are further 

 considered among the reactions of immunity (Chapter vii). 



Results of Phagocytosis. — After phagocytosis has been accom- 

 phshed, the fate of the engulfed object depends upon its nature. If 

 digestible by the intracellular enzymes it is soon destroyed, but in 

 the case of engulfed living cells, it seems probable that they must be 

 first killed — ^they form no exception to the rule that living protoplasm 

 cannot be digested. This brings forward the question of so much 

 importance in the problems of immunity: Do living bacteria enter 

 phagocytes, or are they first killed by extracellular agencies before 

 they can be taken up? At the present time it seems to be positively 

 established that leucocytes do take up bacteria which are still viable, 

 and which may either grow inside the leucocytes or may be destroyed 

 by intracellular processes. ^^ On the other hand, leucocytes do not 

 take up extremely virulent bacteria, and hence the question as to the 

 relative importance played by the leucocytes and by the body fluids is 

 still undetermined. It is probable that phagocytosis by fixed tissue- 

 cells is of much less importance in checking bacterial growth than is 

 phagocytosis by leucocytes. Thus Ruediger's experiments showed 

 that emulsions of organs, with the exception of bone-marrow, do not 

 destroy streptococci which are readily destroyed by leucocytes. How- 

 ever, the phagocytic activity of certain endothelial cells, especially in 

 lymph sinuses and the Kupffer cells of the liver, is so great that these 

 cells may equal or surpass the leucocytes in bactericidal power. Leu- 

 cocytes do not seem to bind bacterial toxins. ^^ 



Indigestible substances may remain in cells, particularly in fixed 

 tissue cells, for very long periods, if the substances are chemically in- 

 ert. The leucocytes seem to transfer the indigestible particles which 

 they have engulfed to other tissues, particularly to the lymph-glands; 

 this is probably accomplished by phagocytosis of the laden leuco- 

 cytes by the macrophages of the lymph sinuses, but how the insoluble 

 particles are later transferred to the gland stroma or perilymphangial 

 tissues, where they are chiefly found in such conditions as anthracosis, 

 etc., is quite unknown. 



" Briscoe, Jour. Path, and Bact., 1907 (12), GO. 



" See Iluediger, Jour. Amcr. Med. Assoc, 1905 (44). 19S. 



"* Pettersson, Zcit. Ininninitat., 1911 (S), 498. Koozarenko, however, states 

 that horse leucocvtos ucutrnli/.c diphtheria but not tetanus to.\in. (Ann. Inst. 

 Pasteur, 191.'') (29), 190.) 



