106 



LABORATORY COURSE IN SERUM STUDY 



Complement fixation is even more delicate a method of identifying 

 a protein than is the precipitin reaction. 



Reagents : 



1. Serum of rabbit immunized against human serum, diluted 1-5. 1 



2. Human serum, diluted 1-5. 



3. Guinea pig serum, diluted 1-10. 



4. Washed sheep cells, 5% suspension. 



5. Serum of rabbit immunized against sheep cells (antisheep-cell 



amboceptor). 



Set up the following tubes : 



Bring all volumes to 2 c.c. 



Incubate mixtures one hour at 37 C. 



Sensitize sheep cells by adding two units of antisheep-cell serum to 

 each 0.5 c.c. of cells. 



At the end of the hour add a dose of these sensitized cells to each 

 tube. (The dose is 0.5 c.c. of 5 per cent cells + the proportionate vol- 

 ume of amboceptor.) 



Incubate until haemolysis is complete in control tubes 4, 5 and 6. 



Tube 4 is inserted as a control test to show that fixation is not given 

 with serum in general but only with human serum. Different students 

 use the sera of different animals as control. If monkey serum is avail- 

 able, let some of the students set up control tests with it. 



Compare the dilution of human serum which still gives a positive 

 reaction with the titer which gave a precipitin reaction with the same 

 antiserum in Lesson VII. 



1 Where dilutions are made to economize material they must not be taken 

 to have any significance of principle. 



2 (Make a preliminary dilution of 1-20 and add 0.5 c.c. and 0.1 c.c.) 



