Repression of colony‐forming ability of C57BL hematopoietic cells transplanted into non‐isologous hosts

The present experiments have shown that a suspension of cells derived from C57BL mice consistently yields a lower value for the CFU content when tested in irradiated (C57BL X C3H)F1 recipients than when tested in irradiated isologous recipients, though the ability of the transplanted cells to enhance survival of the irradiated mice remains similar in both cases. This effect is termed CFU repression. The results of experiments designed to delineate this phenomenon do not permit us to make a ready identification of CFU repression with any of the well-established phenomena of tissue transplantation. Though the mechanism of CFU repression remains obscure, its elucidation may provide valuable information about the factors influencing the development of spleen colonies.