794 PASSIVE IMMUNIZATION SERUM THERAPY 



ing dilutions are injected intraperitoneally two hours before the injection of 1 M. L. D. 

 culture. These protection tests have been found to parallel the extent of immuni- 

 zation more closely than agglutination or complement-fixation tests. 



Action of Antimeningococcus Serum. As previously stated, ex- 

 periments in vitro show that a potent antimeningitic serum possesses 

 three chief antibodies upon which its curative powers probably depend, 

 namely: (1) Bacteriotropins (immune opsonins), which lower the re- 

 sistance of the meningococci and facilitate their phagocytosis; (2) 

 bactericidins, which kill the cocci extracellularly, either with or without 

 final lysis; and (3) antitoxins, which neutralize the true extracellular 

 toxin, which some strains of meningococci apparently produce in varying 

 degree. Other than these are the agglutinins, which probably aid in 

 bacteriolysis, and anti-aggressins, which may assist in the process of 

 phagocytosis. 



Microscopic examination of a direct stained smear of the sediment of 

 cerebrospinal fluid obtained from fresh cases will show large numbers of 

 polynuclear leukocytes and cocci, the majority of the latter being ex- 

 tracellular. As the case improves, whether under serum treatment or 

 spontaneously, the microorganisms diminish in number and become 

 intracellular, frequently appearing clumped and failing to grow in 

 culture. It would appear, therefore, that a cure is brought about 

 partly by means of phagocytosis aided by bacteriotropins; by bacte- 

 riolysis through the agency of specific bacteriolytic amboceptors in the 

 immune serum and complements in the spinal fluid and blood-serum, and 

 to some extent by neutralization of a toxin with antitoxin. 



A potent antimeningococcus serum furnishes these main antibodies, 

 and since the first two must act locally upon the cocci infecting the 

 meninges, the serum must be applied locally and directly by intra- 

 spinous and subdural injection, since only traces of immune serum could 

 eventually find their way into the cerebrospinal fluid if the serum were 

 injected subcutaneously or intravenously. On the other hand, in the 

 treatment of meningococcus bacteremia and toxemia the serum should 

 be injected intravenously and subcutaneously. 



Unfortunately, an immune serum may not contain the antibodies 

 for the cocci producing a given infection, and hence the serum, even 

 though it is skilfully administered in large doses, will have no influence 

 upon the disease. Apparently the cocci of these resistant or "fast" 

 strains are uninjured by the antibodies in the serum. To overcome this 

 difficulty, a large number of different strains of meningococci are used 

 in immunizing horses. If, however, the serum of one laboratory is 



