A. Poggi et al., EXTRATHYMIC DIFFERENTIATION OF T-LYMPHOCYTES AND NATURAL-KILLER-CELLSFROM HUMAN EMBRYONIC LIVER PRECURSORS, Proceedings of the National Academy of Sciences of the United Statesof America, 90(10), 1993, pp. 4465-4469
Liver cells were isolated on Ficoll/Hypaque gradients from embryos or
fetuses at 6-10 weeks of gestation; 2-20% of the cells expressed CD45
or HLA class I surface antigens and 2-6% expressed CD7. Other T- or na
tural-killer (NK)-cell-lineage-specific markers were undetectable. Liv
er-cell suspensions cultured in the presence of phytohemagglutinin and
recombinant interleukin 2 gave rise to large proportions of CD3+ lymp
hocytes expressing either alpha/beta or gamma/delta T-cell receptors.
This occurred not only in bulk cultures but also when cells were clone
d under limiting dilution conditions. Importantly, these figures were
obtained also in embryos at 6-8 weeks of gestation, which is before co
lonization of the thymic rudiment by T-cell precursors. When the same
liver-cell suspensions were cultured in the presence of irradiated H9
cells and recombinant interleukin 2 (either in bulk cultures or under
cloning conditions), large proportions of cells (or clones) expressed
surface CD16 and CD56 antigens and displayed a strong cytolytic activi
ty against both NK-sensitive (K562) and NK-resistant (M14) target cell
s. In addition, liver-derived T or NK cells expressed functional recep
tor molecules since they could be activated via either CD3/T-cell rece
ptor or CD16 surface antigens, respectively. Further fractionation of
liver cells on the basis of CD45 antigen expression indicated that onl
y CD45+ cells could give rise to T or NK cells in culture. Thus, CD45
can be used as a marker for identification of an early liver-cell popu
lation containing T- and NK-cell precursors. That T or NK cells were d
erived from male embryos and not from the mother was shown by PCR ampl
ification of X and Y chromosomal sequences. Our present data may offer
an in vitro model for extrathymic embryonic T-cell maturation that ca
n be used to examine fundamental aspects of human T-cell development a
nd function.