684 PASSIVE IMMUNIZATION SERUM THERAPY 



bacteria, and in this manner facilitating phagocytosis. Other antibodies 

 may be operative and prove of assistance, as, e. g., agglutinins may aid 

 in bacteriolysis and anti-aggressins may aid in phagocytosis, but too 

 little is known at the present time to allow fine distinctions to be made, 

 although the indications are that not one but several antibodies are present 

 in each immune serum, which, acting together, tend to overcome an in- 

 fection. 



From the practical standpoint, therefore, immune serums may be 

 used to produce two main types of passive immunization, namely: 



1. Antitoxic immunization, due to antitoxins for the true or extra- 

 cellular toxins, as in diphtheria and tetanus (antitoxic immunity). 



2. Antibacterial immunization, due mainly to bacteriolysins and bac- 

 teriotropins, as in meningococcus, pneumococcus, streptococcus, gono- 

 coccus, and similar infections (antibacterial immunity). 



The mechanism of both of these varieties of passive immunity will be 

 considered briefly under their respective headings. 



INDICATIONS FOR PASSIVE IMMUNIZATION 



For purposes of prophylaxis only two immune serums have proved 

 their efficiency, namely, the antitoxin of diphtheria and tetanus anti- 

 toxin. 



As will be pointed out further on, diphtheria antitoxin, when ad- 

 ministered in sufficient amounts, affords protection for at least from four 

 to six weeks; mixed immunization, by means of the simultaneous in- 

 jection of a neutral mixture of the toxin and antitoxin, as worked out by 

 von Behring, has been found to yield equally good and more prolonged 

 immunity, but because of certain technical difficulties has not as yet 

 been widely adopted. 



Tetanus antitoxin has its greatest value as a prophylactic. When 

 symptoms of tetanus have once appeared, serum treatment may be of no 

 avail, whereas it has proved its efficiency beyond doubt in neutralizing 

 the toxin before it reaches or unites with the nervous tissue. In all 

 wounds likely to be infected with tetanus the physician should include 

 the administration of tetanus antitoxin as a matter of routine treatment. 



Of the antibacterial serums, many have a prophylactic value in ex- 

 perimental animals, but none, with the exception of the antiplague 

 serum, is in general use as a prophylactic in human practice. The rea- 

 sons for this are apparent when it is remembered that pneumococcus, 

 streptococcus, and meningococcus infections are not sufficiently epidemic 





