50 



D. A. L. DAVIES 



produced and it was necessary to wash out the cells, which 

 was done with pH 7*2 buffered saline (BS). Some relevant data 

 are shown in Table II. The LAN "non-specific" tumour fluids 

 (this tumour is not altogether without specificity — see below) on 

 centrifuging give packed cells occupying half of the total volume 

 of the fluid and therefore show an artificially low value for the 

 weight of soluble material in the ascitic fluid after dialysis and 

 freeze drying. The two leukaemias, CL2 and EL4, give a very 

 small yield when compared with LAN, BP8 and other tumours 

 tested, but give a relatively higher yield of H-2 antigen. 



Table II 

 Mouse tumour products 



Products of 1,000 mice 



Peritoneal contents were centrifuged slowly at room tempera- 

 ture to separate tumour cells from red cells ; LAN was chosen in 

 preference to the Ehrhch, Krebs, and other non-specific tumours 

 tested, because it was less haemorrhagic. EL4 generally gave few 

 red cells in the peritoneum but BP8 and CL2 usually required 

 repeated slow sedimentation from BS before the red cells were 

 wholly removed. The washed tumour cells were freeze dried and 

 stored at — 20°c to await extraction of antigens other than H-2. 

 The BS washings of tumour cells had little H-2 activity and were 

 discarded. The original ascitic fluid supernatants were centrifuged 

 at high speed in a continuous flow centrifuge (Alfa Laval) to 

 remove residual cells and debris before dialysis. 



Dialysis against distilled water gave an insoluble fraction of 



