ABROGATION OF ALLOGENEIC INHIBITION BY CORTISONE.

Tumor cells from homozygous mice grow better upon transplanation to syngeneic mice than to F(1) hybrids between the tumor strain and a foreign strain. The inhibition of cell growth in the hybrids (called allogeneic inhibition), which is detected by tumor transplantation into mice, cotuld be abrogated by treatment of the recipient mice with cortisone acetate. Cortisone also abolished allogeneic inhibition in vitro; abolition was detected by treating tumor cultures with cell extracts containing foreign isoantigens of the H-2 type.

GROWTH INHIBITION OF SARCOMA AND CARCINOMA CELLS OF HOMOZYGOUS ORIGIN.

Three sarcomas and one carcinoma, originating in homozygous mice, were tested for growth in isologous animals and various semi-isologous F(1) hybrids after inoculation of 10(3) to 10(5) cells. Findings indicated the existence of an "F(1) hybrid effect" for sarcomas and carcinomas, as previously described for lymphomas and normal hematopoietic cells, there being a lower tumor frequency and a longer latency period in the hybrids than in isologous mice.