Reconstitution Properties of Thymus Stem Cells in Murine Fetal Liver

摘要

Injection of day-12 murine fetal liver cells into thymus lobes of Thy-1 congenic adultrecipients results in a wave of thymocyte development. The kinetics of repopulation bydonor cells reaches a peak after 20–25 days. The frequency of thymic stem cells (TSC) inday-12 fetal liver was estimated, by limit dilution, as 1 in 4x104cells. Within 8 hr ofinjection into a thymus lobe, fetal liver TSC commit to T-cell development, losing stem-cellactivity. When fetal liver cells are maintained in culture for 7 days, with no exogenouscytokines added, and then injected intra-thymically (I.T.), thymus recolonization is notobserved. However, TSC can be maintained in culture for 7 days with IL-1β, IL-3, IL-6, orLIF added, alone or in combination, with steel factor (SLF). Poisson analysis of fetal livercells cultured with SLF and IL-3 together revealed a precursor frequency of 1 in 1.8x 105cells. In contrast, the frequency of TSC in adult bone marrow was estimated by limitdilution as 1 in 12,000 cells.