Ability of thymic lymphocytes to alter CFU kinetics in radiation chimeras

It is known that the poor colony-forming ability of B6 bone marrow transplanted into B6D2F1 hybrids can be improved if B6 lymphocytes are given in addition. It was recently reported that the augmenting lymphocytes decrease the doubling time of differentiating hemopoietic cells. To determine whether thymus cells alter the self-renewal of CFUs in this parent leads to F1 combination, retransplantation and 3H-thymidine 'suicide' were employed as methods to determine the cell-division rate. We have observed that in the presence of thymocytes, parental bone marrow cells are seeded more efficiently in the spleen, and the lag phase of the CFUs growth curve is shortened. However, thymic lymphocytes do not increase the slope of the exponential growth phase of CFUs.