Studies on Immunity to Leukemia L1210 in Mice.

suspensions from DBA/2 mice. Under the same conditions any immune response in DBA/2 mice was doubtful. Pretreatment with normal or x-radiated normal DBA/2 spleen did not protect CDBA animals against L1210 challenge. DBA/2 skin grafts were rejected by a proportion of normal CDBA animals and by CDBA animals preimmunized with L1210. The rejections were late—about 140 days for normal animals and 93 days for the immune mice. Control grafts of CDBA or of BALB/c skin were uni formly accepted. Possible explanations for the unexpected rejection of DBA/2 skin grafts by the Fi hybrids are considered. The variation in response to L1210 between DBA/2 and CDBA animals is discussed with reference to possible approaches for alter ing the host-tumor relationship so as to augment the effect of chemotherapy.