104 



LABORATORY COURSE IN SERUM STUDY 



hsemolytic action of complement then use 0.1 c.c. of emulsion in the 

 tests as follows : 



Incubate 1 hour at 37 C. Add to all tubes 0.5 c.c. of sensitized 

 cells and incubate again. 



Tubes 2 and 3 are necessary control tests in all complement fixation 

 work, to prove that under the precise conditions under which comple- 

 ment is fixed in Tube 1 it is not fixed by antigen alone or by antiserum 

 alone. 



Materials for each student : 



6 half-inch test tubes. Test tube rack. 

 4 large test tubes. 

 24 hour typhoid culture. 



Platinum loop. 

 6 one-c.c. pipettes 



1.5 c.c. immune antityphoid serum (diluted). 

 4.0 c.c. 5 per cent sheep cell emulsion. 

 4.0 c.c. 10 per cent guinea pig serum. 

 15 units amboceptor. 

 Salt solution. 



LESSON XVII 



ALEXIN FIXATION BY DISSOLVED PROTEINS AS ANTIGENS 

 (AND BY SPECIFIC PRECIPITATES) 



THE phenomenon of fixation of alexin by the union of antiserum 

 and antigens is not limited to cellular antigens, but occurs when- 

 ever a serum containing antibodies is mixed with its corresponding 

 protein antigen in the presence of alexin, or when alexin is treated 

 with the precipitate so obtained. The binding of complement 

 does not, however, depend on the formation of a precipitate, for 

 it occurs in dilutions at which a precipitate no longer can be seen. 



