292 GUY A. VOISIN AND RADSLAV KINSKY 



II. Methods 



A. Preparation of facilitating antisera 



CBA adult mice received tissues from A-strain mice, either 

 normal lyophilized tissues or living tumour tissues. 



(i) Normal lyophilized tissues 



The immunization schedules of animals receiving lyophilized A 

 newborn and spleen tissues corresponded to that used by Kahss 

 (personal communication) for lyophilized tumour or splenic 

 tissues. Five injections of o- 5 ml. suspension each were injected 

 intraperitoneally at regular intervals within 3 weeks. Blood was 

 withdrawn 10 days after the last injection and sometimes once 

 more 4 days later. Occasional booster injections (up to 4) were 

 followed by bleedings 5 to 7 days later, with sometimes one more 

 bleeding 4 days later. 



(2) Living tumour tissues 



Subcutaneous inclusions of approximately 200 mg. of Hving, 

 non-infected, non-necrotic tumour tissue were performed on 

 CBA recipients and the animals bled 10 and 18 days later. By 

 this time the transplanted tumours had stopped growing and after 

 20 days a regression was observed. Blood was drawn through a 

 perpendicular incision of the caudal artery. The sera obtained 

 were stored at —20°. 



B. Tests for activity of the antisera 



(i) In vitro: haemagglutination 



Gorer's haemagglutination test (Gorer and Mikulska, 1954) 

 was adopted, using as medium absorbed human serum with 

 dextran. The human serum was absorbed at 4° first with rat red 

 blood cells (RBC), as suggested by Amos (personal communica- 

 tion through Dr. Ha ward), then with miscellaneous (various H-2 

 alleles) mouse erythrocytes. We found it technically more 

 convenient to mix the A-strain RBC-CBA serum dilution 



