810 PASSIVE IMMUNIZATION SERUM THERAPY 



bility to reinfection may be increased because of lowered local and gen- 

 eral resistance due to the previous attack. 



Antipneumococcus Serum. The indications of specific serum 

 therapy, are, therefore, mainly twofold: first, to destroy any pneumo- 

 cocci present in the blood and in the local lesion; or if the latter is im- 

 possible because of mechanical obstacles that interfere with the circula- 

 tion and prevent access of the antibodies to the cocci, to at least prevent 

 extension of 'the lesion by preventing the multiplication of organisms at 

 its margin; second, to neutralize the toxins produced during the course 

 of the disease. 



It would, of course, be highly desirable to have at our command a 

 serum that would cause solution of the local exudate and bring about a 

 crisis and a cure. It is hardly reasonable to expect, however, that a 

 serum can be produced that will contain digestants for fibrin and leuko- 

 cytes. The local lesion is most likely to be harmful because of the toxic 

 substances that emanate from it, and not because so large an area of 

 lung is temporarily incapacitated and the heart embarrassed. A serum 

 that will prevent general bacteremia, limit the extension of the local 

 lesion, and neutralize the toxins while nature is preparing to react upon 

 the exudate with a ferment, is probably fulfilling all that may be ex- 

 pected of a specific serum therapy. 



Groups of Pneumococci. Neufeld and Handel have shown that an immune 

 serum produced by the injection of a given variety of pneumococci into an animal 

 was not effective against all forms of pneumococci. In the Rockefeller Hospital a 

 serum, known as Serum 1, prepared by immunizing a horse with a culture obtained 

 from Neufeld, was found to protect against only about one-half the types of pneu- 

 mococci (Group 1) studied. By immunizing rabbits to each of the types that were 

 not acted upon by Serum 1, and testing the immune serum against all strains by 

 cross-agglutination and by cross-protection experiments, it was found that a number 

 of the serums possessed the same properties, thus indicating that their respective 

 cultures belonged to the same general group (Group 2). By immunizing a horse with 

 one of these, Serum 2 was produced. In Group 3 are placed all the organisms of the 

 so-called Pneumococcus mucosus type. In Group 4 are included all the varieties of 

 pneumococci against which Serums 1 and 2 are not effective, and which, from their 

 other properties, do not belong in Group 3. Animals may readily be immunized to 

 any member of this Group 4, and the serum of the immunized animal is protective 

 against the strain used for immunization, but in no instance has this serum been 

 found effective against any other member of this group or against the organisms of 

 the other groups. While no cultural or morphologic differences between the members 

 of Group 1, 2, and 4 exist, it has been found possible to group them by the aggluti-, 

 nation reaction in exactly the same manner as by protection experiments. Of 

 24 strains studied in the Rockefeller Hospital, 47 per cent, belonged to Group 1, 

 18 per cent, to Group 2, 13 per cent, to Group 3, and 22 per cent, to Group 4. 



Determining the Type of Pneumococcus. The method is described on page 308. 



Preparation of Antipneumococcus Serum. Horses are immunized with dead 

 and then with virulent living cultures. In view of the fact that the serum should 



