GRAFT SIZE CONSIDERATIONS IN KINETICS OF SPLEEN COLONY DEVELOPMENT

The kinetics of spleen colony development has been studied after the injection of 106, 105 and 3 × 104 bone marrow cells. The results indicate that: The CFU population growth rate is independent of cell dose until the logarithmic growth phase is passed. Slowing of growth was seen by day 12 after the highest dose, by day 15 after the median dose, but was not observed during the period of observation after the low dose. The growth rate of CFU per colony is independent of cell dose, but the curves are not identical. The differences between the curves leads to the conclusion that there is a dose‐dependent delay in the commencement of CFU proliferation. The delay is roughly equal to one cell cycle time between the medium and high inoculum groups and also between the medium and low inoculum groups. The number of cells per colony is graft size dependent, the doubling times, where these can be roughly assessed, being inversely related to the graft size. From the average number of cells per colony on day 6 it is calculated that the mean doubling time in the early stages of colony development is less than 7 hr. The proportion CFU:colony cells is dose dependent with the highest inoculum having the highest proportion and the low inoculum group having the lowest proportion. Copyright © 1969, Wiley Blackwell. All rights reserved