THE CHEMICAL MECHANISMS OF DEFENCE 1037 



has been heated. The serum separated from the corpuscles has thus lost the 

 amboceptor, but retained the complement. The amboceptor is found to have 

 attached itself to' the red blood-corpuscles. If these be washed and then 

 added to normal sheep's serum, i.e. serum containing the complement, they 

 are rapidly dissolved. When solution has taken place both complement and 

 amboceptor are found to have disappeared. The function of the amboceptor 

 thus seems to be to enable the complement already present in normal serum 

 to act upon the red blood- corpuscles. We may regard the amboceptor 

 therefore as having two haptophore groups, one of which anchors on to the 

 red blood-corpuscle, while the other attaches itself to the complement 

 (Fig. 484, 7). The amboceptor plus the complement thus comes to resemble 



FIG. 484. Diagram to show the relation of amboceptor and complement 

 to the animal cell (7) and to red corpuscles (8). (EHRLICH.) 



the toxin molecule, having a free haptophore group at one end and a toxo- 

 phore group (the complement) at the other end. The reaction to the injec- 

 tion of the red blood-corpuscles consists in the formation of the amboceptor, 

 which is essentially the anti-body of the red blood- corpuscle (Fig. 484, 8). 

 Similar specific anti-bodies effecting the dissolution of cells or organisms 

 may be produced by the injection of various species of bacterium or of 

 animal cells, such as leucocytes, spermatozoa, liver-cells, &c., and there can 

 be no doubt that bacteriolytic substances play a considerable part in acquired 

 immunity. 



OPSONINS. In some cases the antibodies produced by the injection 

 of living or dead micro-organisms do not bring about actual destruction of 

 the bacteria, but alter them in such a way as to make them more susceptible 

 to the action of the phagocytes. If washed white blood-corpuscles be mixed 

 with micrococci, such as those found in an ordinary boil, they are found to 

 take up the micro-organisms in considerable numbers. The numbers taken 

 up are much increased in the presence of serum derived from an individual 

 who has received repeated minute injections of the dead micrococci in 

 question. To the substances in the serum which thus prepares the micrococci 

 for ingestion by the phagocytes Wright has given the name of opsonins. 



