244 



HILDEMANN, LINSCOTT AND MORLINO 



considered to be technical losses and are not included in the 

 results. 



When newborn A/Jax mice each received two million adult 

 C57BL/6 small lymphocytes, 35/45 or 77-9 per cent died of runt 

 disease, whereas 40/45 or 89 per cent gave evidence of graft- 

 versus-host reactions. Although the incidence of runt disease was 

 substantially greater at this higher cell dosage, the time-mortahty 



T— yA 



J 



10 15 20 



DAYS AFTER INJECTION 



Fig. 2. The time distribution of deaths of 63 A/Jax mice that received 

 0-9-1 '5 milhon C57BL/6 small lymphocytes via the heart during the 



day of birth. 



distribution revealed no acceleration of the syndrome. Thus an 

 MST of 17*4 (15 •6-19* 6) days was calculated for the normal 

 distribution, whereas an MST of 19-9 (17- 8-22* 3) days was 

 obtained on the assumption of a truncated distribution with 

 n = 45. Technical difficulties in the isolation of viable blood 

 lymphocytes in higher dosage have not yet been surmounted. 

 More highly concentrated preparations than those obtained by the 

 straightforward filtration-centrifugation procedure described 

 contained so many red cells that immediate or very early death 

 resulted when newborns were injected by the intracardiac route. 



