Attempts to immunize F1 hybrid mice against their parents.

Attempts were made to immunize F hybrid mice to their inbred parental strains by active immunization with either living or dead parental cells and by adoptive transfer of isogenic (F) lymph node cells to irradiated hybrids that subsequently received parental bone marrow. Cumulative mortality studies and erythrocyte serotyping revealed that many mice survived and retained their parental grafts for long periods of time. In most experiments reported here, Fe uptake by erythrocytes and spleens of chimeras 1 week after marrow transplantation was used as a measure of erythropoiesis and thereby of success or failure of the marrow graft. Pre-treatment (`pre-immunization') of hybrids with parental spleen cells produced no evidence of specific immunization. However, pre-treatment with spleen cells from parent 1 was detrimental to subsequently transplanted marrow from parent 2 and vice-versa. Adoptive transfer of viable F lymph node cells failed to decrease growth of parental cells in irradiated F hybrids. These findings indicate that the poor-growth phenomenon of particular parent—F combinations cannot be explained in terms of classical immune rejection of parental cells by F hybrids. Instead, growth of parental cells in the F environment is inhibited or delayed.