Differential Effects of IL-2 and IL-6 on the Development of Three Distinct Precursor T-Cell Populations in the Thymus
Differential Effects of IL-2 and IL-6 on the Development of Three Distinct Precursor T-Cell Populations in the Thymus
NAOKO NAKANO
HITOSHI KIKUTANI
TADAMITSU KISHIMOTO
Three distinct T-cell precursors: bone marrow cells that express low levels of the Thy-1 antigen but no lineage markers (Thy-l-lo/BM); CD4-, CD8-, and CD3- thymocytes that express low levels of the Thy-1 antigen (Thy-l-lo/Thym); and CD4-, CD8-, and CD3thymocytes that express high levels of the Thy-1 antigen and the IL-2 R cz chain (Thy-1 // IL2R /) were isolated by fluorescence-activated cell sorter (FACS). These three populations expanded with different kinetics in the thymus of irradiated recipient mice after intrathymic transfer. When a high dose of human recombinant IL-2 (r-IL-2) or human recombinant IL-6 (r-IL-6) was administered, r-IL-6 accelerated donor Thy-1 +/IL2R to differentiate, whereas r-IL-2 blocked normal differentiation and expansion of donor Thy-l-lo/Thym, but did not show any significant effect on donor Thy-1 //IL2R /. Neither r-IL-2 nor r-IL-6 worked directly on donor Thy-lalo/BM in this transfer system.
IL-2; IL-6; T-cell progenitor; thymic development
-
has been reported to work as a T-cell growth factor
(Le et al., 1988; Uttenhove et al., 1988)
, and it is
possible that IL-6 plays a role in thymocyte
development.
In an attempt to understand the differentiation
process of precursor T cells, we took advantage of
intrathymic injection
(Goldschneider et al., 1986)
,
combining with the three-color
fluorescence-activated cell sorter (FACS) to isolate distinct T-cell
precursors and to chase the fate of only donor-derived
thymocytes in the host thymus. Effects of IL-2 and
IL-6 on the development of T cells were also studied
in this experimental system by administration of a
relatively large amount of human recombinant IL-2
(r-IL-2) or human recombinant IL-6 (r-IL-6) to
recipient mice that had been injected with sorted
precursor T cells.
RESULTS
Capacity of Expansion and the Stage of Development of Precursor T Cells
On the basis of Thy-1 and IL-2-R expression,
double-negative and CD3-negative C3H/HeN
thymocytes were subfractionated into three
populations, IL-2-R / and IL-2-R- thymocytes (Thy-l+/
IL2R / and Thy-I//IL2R -, respectively), both of
which express high levels of the Thy-1 antigen, and
thymocytes with low levels of the Thy-1 antigen
(Thy-l-lo/Thym)
(Nakano et al., 1987)
. Bone marrow
cells expressing low levels of the Thy-1 antigen
(Thy-l-lo/BM), which have been demonstrated to
give rise to T cells as well as all lineages of
hematopoietic cells
(Muller-Sieburg et al., 1986)
, were also
sorted from C3H/HeN bone marrow cells as another
source of precursor T cells. Sorted precursor T-cell
populations were intrathymically injected into
sublethally irradiated AKR/J recipients and examined
for their ability to reconstitute the recipient
thymuses.
T cells derived from injected precursor cells were
chased by staining the Thy-l.2 antigen, which
allows distinguishing T cells of donor origin from
those of host AKR/J (Thy-l.1), and Fig. 1A shows
kinetics of expansion of donor-derived T cells
detected as Thy-l.2 /. When I xl06 Thy-I//IL2R
were injected, cells detectable as Thy-l.2 / tapered
off within a few days and did not expand in the
thymuses of irradiated recipients. In the recipient
thymuses injected with 2x10 Thy-I+/IL2R / cells,
B
a
b
Thy-llL2oot
Thy-l-loKhymoot
day 11
day 12
C Thy-l-lo/BM /
0
CD8
00
CD8
CD8
CD8
oo
;o ;oo
CD8
day 18
day 38
Thy-l.2 / donor-derived cells expanded one I//IL2R +, Thy-l-lo/Thym, and Thy-l-lo/BM, all of
hundredfold within 10-14 days and decreased there- which were capable to expand in the thymus, as
after. T cells derived from this precursor population described before. First, irradiated AKR/J recipients
were mostly CD4+/CD8 / on day 11, and gradually were intrathymically transferred with Thy-I//IL2R +
shiftedtoward CD4 //CD8- and CD4-/CD8 / on day C3H/HeN cells and then injected with saline, 10 g
18, Fig. 1B(a). A delay in expansion of donor- of r-IL-2, or 10 g of r-lL-6 every day. By gating on
derived thymocytes was observed when I xl0 Thy- donor-derived Thy-l.2 positive cells, the expression
1-1o/Thym was injected. Although cells detected as of CD4 and CD8 on the donor-derived thymocytes
Thy-l.2 / expressed mostly both CD4 and CD8 on was analyzed on day 11. As shown in Fig. 2A,
day 12, their cell number was only tenfold higher surface phenotypes of donor-derived cells were
than that of injected cells, Fig. 1A and Fig. 1B(b). mostly CD4+/CD8 / at this point. The relative
proThey continued to expand and reached the portion of CD4-/CD8-cells in r-IL-6-treated mice
maximum level on day 21 with one hundredfold was lower than in the control, Fig. 2A(c). The
absoexpansion. As shown in Fig. 1B(b), the differentiated lute number of donor-derived cells in r-IL-6-treated
cells such as single positive cells were observed on recipient thymus was found to be several times
day 21. The (...truncated)