124 The Chemistry of the Injured Cell 



with albumin and «i globulin. The active principle is probably 

 neither of these proteins but is more likely to be a highly soluble 

 protein with a considerable carbohydrate component in its mole- 

 cule. The substance is non-dialysable, relatively heat-labile, in- 

 soluble in 5 per cent trichloracetic acid and inactivated by trypsin. 

 In its origin in leucocytes, its presence in the fluid phase of leuco- 

 cyte-rich exudates and in skin several hours after injury, and its 

 response to heating, the leucocyte emigration factor resembles the 

 endogenous fever-producing substance demonstrated by American 

 workers. 



There are two possible modes of action for the leucocytic factor 

 that induces polymorph migration. It might exert a chemotactic 

 influence, the white cells being attracted through a vessel wall whose 

 properties have been altered by other influences, e.g. histamine, 

 globulins or peptides. Alternatively, the leucocyte migration factor 

 might itself induce a change in vessel walls rendering them specific- 

 ally permeable to white cells and this hypothesis seems the more 

 likely. Accumulation of polymorphs around a bacterial colony or 

 foreign body in the tissues is no proof of chemotaxis by the colony 

 or foreign body, since the white cells may have arrived at their 

 destination by random migration and then had their progress or 

 their life terminated by toxic influences. The relative dissociation 

 of vascular permeability to protein on the one hand and to leuco- 

 cytes on the other suggested by the results presented above may 

 seem remarkable. It may be explained, however, by assuming that 

 much of the protein escapes into the tissues by passing through the 

 cytoplasm of the endothelial cell (Alksne, 1959) , whereas the 

 leucocytes may leave the vessel by making their way between the 

 endothelium. Thus two distinct but normally coexistent mechan- 

 isms may be involved. The mode of action of the leucocyte emigra- 

 tion factor is of course unknown but in view of the known enzymic 

 properties of leucocytes it seems possible that the active principle 

 of leucocyte extracts may be a mucopolysaccharidase or other 

 enzyme which attacks the constituent substances of the vessel wall. 

 When large numbers of leucocytes have collected in the tissues, pus 

 may be formed. Pus is the creamy viscous fluid derived from the 

 autolysis of dead leucocytes (although it may contain the liquefied 



