174 LABORATORY COURSE IN SERUM STUDY 



LESSON XXX 

 TITRATION OF IMMUNE OPSONIN BY DILUTION METHOD 



INTRODUCTORY REMARKS 



THERE are several methods of titrating the opsonic power of 

 a serum. The most accurate method probably is that in which a 

 number of progressively increasing dilutions of the serum are 

 made and the opsonic power of each dilution is tested. In this 

 way the degree of dilution at which the opsonic power of the serum 

 disappears, that is, at which there is not more phagocytosis in 

 the specimen with this serum than there is in a control with salt 

 solution, is determined. In this way two sera can be compared 

 as to their opsonic strength. It is the method first used by Klein 

 in the case of typhoid opsonins, and the one utilized by Jobling 

 in the standardization of anti-meningococcus serum. 



Reagents : 



1. Suspension of Staphylococcus aureus from 24-hour agar slant. 



2. Suspension of leucocytes obtained from peritoneum of guinea 

 pig injected with aleuronat. 



(The method of preparing these two suspensions has been given in 

 a previous lesson.) 



3. Serum of rabbit immunized against Staphylococcus aureus. 

 Before beginning the experiment 0.2 c.c. of this serum should be 



placed in test tube and heated one half hour at 56 for Series III below. 



4. Serum of normal rabbit. 



Prepare dilutions of each of the sera, 1-5, 1-10, 1-20 and 1-100. 



I 



Set up a series of six tubes. In the first put 0.25 c.c. of undiluted 

 immune serum, in the next four 0.25 c.c. of 1-5, 1-10, 1-20 and 1-100 

 dilutions respectively, and in the last tube 0.25 c.c. of salt solution for 

 control. 



II 



Set up a similar series with normal serum, omitting the fifth and 

 sixth tubes. 



