Jm. Bertho et al., CD135 (Flk2/Flt3) expression by human thymocytes delineates a possible role of FLT3-ligand in T-cell precursor proliferation and differentiation, SC J IMMUN, 52(1), 2000, pp. 53-61
The expression of the Flk2/Flt3 molecule (CD135), the receptor for Flt3 lig
and (FL), was investigated in the human thymus. Results showed that there i
s a high level of expression of CD135 by thymocyte populations, especially
by intrathymic T-cell precursor populations. As these results suggested a r
ole for FL in the regulation of thymic T-cell precursor differentiation and
/or proliferation, we used an in vitro model of thymic stromal cell culture
s in order to delineate the activity of FL on human CD7(high)CD3(-)CD4(-)CD
8(-) triple negative intrathymic T-cell precursors. Results showed that FL,
either alone or in combination with stem cell factor (SCF) induced the pro
liferation of CD7(high) precursors, but to a lower extent than interleukin-
7 (IL-7) or IL-7 + SCF, used as positive controls. In the presence of FL SCF, CD7(high) cells developed mainly towards a CD11b(+) phenotype whereas
IL-7 + SCF preferentially induce a CD3(+)TcR gamma delta(+)CD8(+) phenotype
. Taken together, these data suggest that FL may play a role in inducing th
e proliferation of CD7(high) human intrathymic T-cell precursors, but also
in the induction of a myeloid differentiation pathway within the human thym
us.