D. Dunon et al., ONTOGENY OF THE IMMUNE-SYSTEM - GAMMA DELTA AND ALPHA/BETA T-CELLS MIGRATE FROM THYMUS TO THE PERIPHERY IN ALTERNATING WAVES/, The Journal of experimental medicine, 186(7), 1997, pp. 977-988
The embryonic thymus is colonized by the influx of hemopoietic progeni
tors in waves. To characterize the T cell progeny of the initial colon
ization waves, we used intravenous adoptive transfer of bone marrow pr
ogenitors into congenic embryos. The experiments were performed in bir
ds because intravenous cell infusions can be performed more efficientl
y in avian than in mammalian embryos. Progenitor cells, which entered
the vascularized thymus via interlobular venules in the capsular regio
n and capillaries located at the corticomedullary junction, homed to t
he outer cortex to begin thymocyte differentiation. The kinetics of di
fferentiation and emigration of the T cell progeny were analyzed for t
he first three waves of progenitors. Each progenitor wave gave rise to
gamma/delta T cells 3 d earlier than alpha/beta T cells. Although the
flow of T cell migration from the thymus was uninterrupted, distinct
colonization and differentiation kinetics defined three successive wav
es of gamma/delta and alpha/beta T cells that depart sequentially the
thymus en route to the periphery. Each wave of precursors rearranged a
ll three TCR V gamma but displayed a variable repertoire. The data ind
icate a complex pattern of repertoire diversification by the progeny o
f founder thymocyte progenitors.