COMPLEMENT FIXATION 177 



added, followed by another period of incubation. In this particular 

 instance they employed ox blood-cells and immune serum prepared by 

 injection of ox blood-cells into the rabbit. 



MODIFIED PROTOCOL FROM NEISSER AND SACHS 



Immune serum Complement fixation 



i-io dilution Series A Series B 



1.0 C.C. + 



0.75 c.c. 



0.5 c.c. 



0.35 c.c. 



0.25 c.c. +++ 



0.15 c.c. ++ 



O.I C.C. + 



O.O C.C. 



The above protocol shows that in the strong concentration of im- 

 mune serum the fixation of complement is not as marked as in some- 

 what weaker concentration. Nevertheless, there also comes a point 

 when the concentration is too dilute to permit of fixation. The tubes 

 in series B show that the concentration of human serum in itself is not 

 sufficiently great to prevent the hemolytic reaction. Two points are 

 of interest in this connection. In the first place, it is possible to add 

 immune serum or other serum in amounts so large that the serum itself 

 will have inhibitory action upon the complement. Under optimal con- 

 ditions immune serum may be diluted to an extreme degree and still 

 act as a complement-fixing body; for example, Friedberger, by the 

 use of a well-prepared serum was able to demonstrate complement 

 fixation by an immune serum diluted 1-1,000,000,000. The same deli- 

 cacy has not been confirmed by other investigators and must be regarded 

 as a scientific curiosity. The dilution of the antigenic protein can be 

 carried to a considerable degree but not usually to the same degree as 

 is possible with antiserum. 



Group Reactions. In the application of the complement-fixation 

 test to the forensic determination of dissolved protein, Neisser and 

 Sachs showed that the group phenomenon also appears. They also 

 showed that the antigenic serum could be very much reduced in amount 

 and still give complement fixation. The following protocol illustrates 

 the manner in which such a demonstration may be made. In setting 

 up the test there was used throughout a constant quantity of o.i c.c. 

 immune serum prepared by the injection of human serum. The anti- 

 genic serum was added according to the amounts indicated in the 

 protocol. Complement was used in amounts of 0.05 c.c. The mixtures 

 were incubated and then beef blood-corpuscles which had been sensitized 

 with a specific anti-beef corpuscle serum were added, the mixtures 

 again incubated and the degree of fixation determined. 



GROUP REACTION MODIFIED FROM NEISSER AND SACHS 



Amounts of Fixation with serum of 



antigenic serum Man Monkey Goat 



0.01 +++ +++ 



0.001 +++ 



o.oooi 4-M- + 



0.00001 . -f 



O.OOOOOI 

 O.O 

 12 



