PASSIVE IMMUNIZATION 469 



serum, thus carrying down the antibodies. They then extracted these 

 precipitates with weak sodium carbonate at 42, and in the super- 

 natant fluid found protective antibodies which agglutinate pneumo- 

 cocci. Huntoon has recently perfected this method of dissociation of 

 antibody from its antigen in a way that promises practical usefulness. 

 He treats large amounts of pneumococci with an excess of antibody, 

 at 3iy 2 . After throwing down the pneumococci with a centrifuge, he 

 now washes them with physiological salt solution, at almost the freez- 

 ing point in order to remove traces of serum, and then treats them at 

 a temperature of about 40 with weak sodium bicarbonate solution, a 

 treatment which, as Landsteiner and others have shown with other 

 organisms, dissociates antibodies in large amounts from the antigen- 

 antibody complex. These antibody solutions, if the volume of final 

 solvent is either at or about one-fourth the original serum volume, is 

 protective in approximately the same degree as the original sera, and 

 is almost or perhaps completely protein free. These antibody solutions 

 of Huntoon are at the present time being used experimentally and 

 promising results have already been obtained. Their intravenous 

 injection produces an initial chill, probably due to the non-specific 

 reaction caused, in our opinion, by traces of bacterial protein in the 

 solution. The cases which we have seen reported, show, however, that 

 subsequently a specific reaction seems to occur which promises to 

 render them perhaps an improvement upon treatment with whole 

 serum. 



Standardization of Pneumococcus Serum. After a considerable 

 amount of discussion as to which of the antibody reactions should be 

 used for pneumococcus serum standardization, it has been generally 

 accepted that standardization by mouse protection is the most reliable 

 method. The pioneer work on such standardization was done largely 

 by Neufeld. Recently, it has been developed by various pneumococcus 

 workers, Wadsworth and Kirkbride, 88 the workers at the Rockefeller 

 Hospital, and a number of the manufacturers of pneumococcus serum. 

 The standardization depends upon the amount of serum necessary to 

 protect a white mouse of 20 grams weight against a standard virulent 

 culture. 



One of the most important points in the standardization is to use 

 a culture of very great and accurately known virulence. This can be 

 produced by passage through mice. The virulence of the organism 



ss Wadsworth and Kirkbride, Jour. Exp. Med., 25, 1918. 



