By
From the * Department of Disease-related Gene Regulation Research (Sandoz), Faculty of Medicine,
The University of Tokyo, Tokyo 113, Japan; and the Department of Medical Chemistry, Faculty of
Medicine, Kyoto University, Kyoto 606, Japan
IL-7R-deficient mice have severely impaired expansion of early lymphocytes and lack T cells.
To elucidate the role of IL-7R on
T cell development, we analyzed the rearrangements of
TCR-
,
,
, and
genes in the thymus of the IL-7R-deficient mice. Southern blot analysis
with a J
1 probe revealed that more than 70% of J
1 and J
2 alleles are recombined to form
distinct V
1.2-J
2 and V
2-J
1 fragments in control mice. On the contrary, no such recombination was detected in the mutant mice. The rearrangements in the TCR-
,
, and
loci
were comparably observed in control and mutant mice. PCR analysis indicated that the V-J
recombination of all the V
genes is severely hampered in the mutant mice. The mRNA of
RAG-1, RAG-2, Ku-80, and terminal deoxynucleotidyl transferase (TdT) genes was equally
detected between control and mutant thymi, suggesting that the expression of common recombination machinery is not affected. These data demonstrated that the V-J recombination of
the TCR
genes is specifically blocked in the IL-7R-deficient mice and suggested the presence of highly specific regulation for TCR
gene rearrangement.
IL-7 is a growth factor for early B and T cell precursors. It
was first characterized by its ability to support the growth of pre-B cells. Subsequently, it has been shown to support
survival and growth of early thymocytes and promote rearrangement of TCR Although T and B lymphopoiesis is severely hampered,
decreased but certain numbers of To test the latter hypothesis, we analyzed the recombination status of TCR loci in the Mice.
IL-7R-deficient mice were established by replacing
the exon 2 with a PGK-neo cassette as described (12). Animals
heterozygous (+/ Southern Blot Analysis.
Thymocyte genomic DNA was digested with HindIII or EcoRI restriction enzyme and electrophoresed through 0.7% agarose gel. The DNA was transferred to
polyvinylidene difluoride filters (Immobilon; Millipore, Bedford,
MA) and hybridized with 32P-labeled probes. The following fragments were used as probes: J PCR Analysis.
Thymocyte DNA was prepared from fetuses
at day 17 of gestation and mice at 4 wk old. PCR was carried out
in a 25 µl reaction mixture containing 0.5 ng template DNA (0.5 µg
for TCR RT-PCR Analysis.
Total RNA was isolated using the AGPC
method as described (24). RNA samples were treated with RQ-1
RNase-free DNase (Promega Corp., Madison, WI) to remove
contaminating genomic DNA. Oligo (dT)-primed cDNA was
prepared by Molony murine leukemia virus RNase H To examine whether the signal from IL-7R
affects the V-J recombination, we compared the rearrangement of the TCR
We next examined adult and fetal thymus DNA by
PCR with V
We next analyzed the rearrangement of other TCR genes by Southern blot analysis.
First, the Southern blot was hybridized with J The rearrangement of TCR Next, PCR amplification with V RAG-1 and RAG-2 are indispensable for
V-D-J recombination, and several other gene products
such as TdT, Ku p70/80 and DNA-dependent protein kinase catalytic subunit are also involved in V-D-J recombination (27). To examine whether the signal from IL-7R affects the expression of these genes, we amplified cDNA
prepared from adult thymocytes of IL-7R +/
TCR There are three significant features in our observation.
First, this blockade is specific for TCR To explain the specific inhibition of TCR and
chains in fetal thymus and fetal
liver cultures (1, 2). In vivo administration of neutralizing
antibodies to IL-7 and IL-7R resulted in the inhibition of
both B and T lymphopoiesis (3, 4). Finally, IL-7- and IL-7Rdeficient mice have severely impaired expansion of early
lymphocytes (5, 6).
T cells have unique features in contrast with
T cells
(7, 8).
T cells expressing specific V
chain appear as several successive waves in the developing thymus and each of them shows specific tissue distribution in the adult mouse.
However, little is known about the mechanism of
T cell
development. In fetal thymic organ culture, addition of IL-7
promotes expansion of mature
T cells but prevents generation of mature
T cells (9). The epithelial cells in the
skin and the gut produce IL-7 (10, 11), and dendritic epidermal T cells proliferate in response to IL-7 (10). Additionally, IL-7 induced rearrangement of V
2 and V
4, but
not V
3 or V
5 genes, and sustained expression of RAG-1
and RAG-2 genes (1, 2). Collectively, these results suggested that IL-7 may be involved in development and
maintenance of
T cells in the thymus and the periphery.
T cells and B cells exist
in the periphery of the IL-7R-deficient mice, and they normally respond to mitogenic stimuli such as Con A and LPS
(12). In contrast,
T cells are completely absent in the
IL-7R-deficient mice as well as in IL-2R-
- and Jak3-deficient mice: no
T cells were detected in fetal and adult
thymus, spleen, skin, small intestine, and liver of IL-7Rdeficient mice (12). Two possibilities can be considered
to explain the lack of
T cells in the IL-7R-deficient mice. The one is that
T cell precursors may completely
depend on IL-7 for their survival and/or proliferation. The
other is that IL-7 may be a key factor for the induction of
the TCR
gene rearrangements in T cell precursors.
T cells remaining in
IL-7R-deficient mice. The V-J recombination was almost
completely blocked in the TCR
locus in the mutant thymus, whereas the TCR
,
, and
loci were rearranged at
comparable levels with control thymus. These results clearly
demonstrated that the signal from IL-7R plays an indispensable role on the induction of TCR
gene rearrangement. Thus, the mouse TCR
locus will provide a unique
system to analyze the mechanism of cytokine-induced gene
rearrangements.
) and homozygous (
/
) for the IL-7R mutation were on the (129/Ola × C57BL/6)F3 hybrid background.
The age of fetuses was determined by scoring for the appearance
of a vaginal plug and taking as day 0 the morning on which the
mating plug was observed. All mice were maintained under the
specific pathogen-free conditions in the Animal Center for Biomedical Research, Faculty of Medicine (The University of Tokyo).
1, a 1.1 kb StyI-HindIII fragment
containing the J
1 segment and its 3
flanking region of genomic
DNA from KN6 (15); J
1, a 3.5 kb EcoRI-HindIII fragment of
TA28.1 (16); J
1, a 2.5 kb SacI fragment of pCDS17 (17); J
2, a
2.3 kb EcoRI fragment of mouse genomic J
region (18). To
confirm equal loading of genomic DNA, the membranes were
hybridized with a 1.3 kb KpnI fragment of mouse RAG-2 cDNA
(19). Southern blots were analyzed and radioactivity was quantitated using a Bio-image Analyzer (Fujix BAS2000; Fuji Film, Tokyo, Japan). The percentage of rearranged alleles was calculated
by normalizing with the radioactivity of the RAG-2 probe.
genes), 50 pmol each primer, 200 mM each dNTP,
and 2.5 U Taq DNA polymerase. For TCR
genes, samples
were amplified for 30 cycles of 45 s at 94°C, 2 min at 50°C, and 1 min at 72°C. For TCR
and
genes, PCR was performed as
described previously (20). The PCR products were electrophoresed in 3% agarose gel, blotted onto nylon membranes, and
hybridized with 32P-labeled oligonucleotide probes. PCR primers
are as follows: V
1.1 and V
1.2, 5
-CTTCCATATTTCTCCAACACAGC-3
; J
2, 5
-ACTATGAGCTTTGTTCCTTCTG-3
; J
4, 5
-ACTACGAGCTTTGTCCCTTTGG-3
;
5
RAG-2, 5
-CACATCCACAAGCAGGAAGTACAC-3
; 3
RAG-2, 5
-GGTTCAGGGACATCTCCTACTAAG-3
. V
2,
V
3, V
4, V
5, J
1, V
1, V
4, V
5, J
1, V
8.2, D
2, and J
2
primers were described previously (20). Oligonucleotide
probes used are as follows: J
2, 5
-CAAATACCTTGTGAAAGCCCGAGC-3
; J
4, 5
-CAAATATCTTGACCCATGATGTGC-3
. J
1, J
1, and J
2 oligonucleotide probes were described previously (20, 22). Radioactivity was analyzed using the
Bio-image Analyzer.
reverse
transcriptase (GIBCO BRL, Gaithersburg, MD) at 37°C for 1 h.
PCR was carried out for 25 cycles of 1 min at 94°C, 1 min at
50°C for hypoxanthine phosphoribosyl transferase (HPRT) or at
55°C for others, and 1 min at 72°C. The PCR products were
electrophoresed in 3% agarose gel, blotted onto nylon membranes, and hybridized with 32P-labeled probes. The following DNA
fragments were used as probes: RAG-1, a 1.4-kb EcoRI fragment
of mouse RAG-1 cDNA (19); terminal deoxynucleotidyl transferase (TdT), a 1.3-kb EcoRI-EcoRV fragment of mouse TdT
cDNA, M16-1b (25); Ku-80, a 540-bp PCR fragment of Ku-80
cDNA; HPRT, a 350-bp PCR fragment of HPRT cDNA. The
RAG-2 probe was described above. The following PCR primers are
used: 5
RAG-1, 5
-GCAATGAGGAAGTGAGTCTGGA-3
;
3
RAG-1, 5
-CTGAGGAAGGTATTGACACGGA-3
; 5
Ku-80,
5
-AGAGGACACTATTCAAGGGTAC-3
; 3
Ku-80, 5
-AGACACTGGTACAATCGCTGAA-3
; 5
TdT, 5
-ACTGCGACATCTTAGAGTCA-3
; 3
TdT, 5
-CTTCCCCTTAGTCCTGTCAT-3
; 5
HPRT, 5
-CTCGAAGTGTTGGATACAGG-3
;
3
HPRT, 5
-TGGCCTATAGGCTCATAGTG-3
. Radioactivity was analyzed using the Bio-image Analyzer.
V-J Recombination of TCR Genes Is Blocked in IL-7Rdeficient Mice.
genes between the thymocytes of
IL-7R +/
and
/
mice. The thymocyte DNA from 4-wk-old mice was digested with HindIII or EcoRI, and a
Southern blot was hybridized with the J
1 probe (Fig. 1 A,
left). The J
1 probe allows the analysis of DNA rearrangements involving not only J
1 but also J
2 and J
3 gene
segments (15). The ES cell DNA showed a 6.6-kb J
1, a
9.0-kb J
3, and a 11.7-kb J
2 germline fragment. The thymocyte DNA from IL-7R +/
mice showed decreased intensity of J
1 and J
2 germline fragments compared with
embryonic stem (ES) cell DNA. Furthermore, a 3.6-kb
V
1.2-J
2 and a 1.4-kb V
2-J
1 fragment was clearly detected in IL-7R +/
mice. Quantification of the radioactivity revealed that 71% and 74% of J
1 and J
2 alleles,
respectively, were rearranged in thymocytes. Because
T cells are only 0.3% of total thymocytes (12), the majority of the V
1.2-J
2 and V
2-J
1 recombined fragments are
derived from
T cells or precursor cells. On the other
hand, no fragment derived from V
1.2-J
2 or V
2-J
1
recombination was detected in IL-7R
/
mice (Fig. 1 A).
This result demonstrates that V
1.2-J
2 and V
2-J
1 rearrangements are almost completely blocked in
T cells
in IL-7R-deficient mice.
Fig. 1.
TCR gene rearrangements in the thymus of
IL-7R-deficient mice. Lane 1, thymocytes from IL-7R +/ mice;
lane 2, thymocytes from IL-7R
/
mice; lane 3, E14.1 ES
cells. The position of HindIIIdigested phage
DNA fragments was shown on the right.
(A) Thymocyte DNA was digested with HindIII. A Southern blot was sequentially hybridized with the J
1 (left), the J
2
(middle), and the RAG-2 (right)
probes. (B) Thymocyte DNA
was digested with EcoRI. A
Southern blot was sequentially
hybridized with the J
1 (left), the
J
1 (middle), and the RAG-2
(right) probes.
[View Larger Versions of these Images (72 + 75K GIF file)]
1.1+1.2, V
2, V
3, V
4, V
5, J
1, J
2,
and J
4 primers. Thymus DNA revealed large amounts of
PCR products with all the V
-J
primer pairs in IL-7R
+/
mice. On the other hand, V-J rearrangement was
greatly reduced in all the TCR
genes in IL-7R
/
thymus; the signal of V
5-J
1 product was 150-fold reduced relative to IL-7R +/
mice, and those of V
1.1-
J
4, V
1.2-J
2, V
2-J
1, V
3-J
1, and V
4-J
1 products
were undetectable in IL-7R
/
mice (Fig. 2 A). Amplification with RAG-2 primers produced roughly the equal amount of PCR products in both IL-7R +/
and
/
thymus, suggesting that approximately the same amount of
DNA was used in this analysis. These results support the
data of Southern blot analysis and suggest that the V-J recombination is almost completely blocked in IL-7R-deficient mice not only in V
1.2 and V
2 genes but also in all
the other V
genes.
Fig. 2.
TCR gene rearrangements in the thymocytes
detected by PCR. Rearrangement of TCR (A),
(B), and
(C) genes. The DNA from thymocytes of fetuses at day 17 of gestation (for V
3-J
1, V
4- J
1, and V
1-J
1 rearrangements) and at 4 wk old (for
V
1.1-J
4, V
1.2-J
2, V
2-
J
1, V
5-J
1, V
4-J
1, V
5-
J
1, and all the
gene rearrangements) was amplified by
PCR, and the Southern blots of
the products were hybridized
with oligonucleotide probes.
Combination of primers used are
shown on the left side (A and B).
D
-J
2 and V
8.2-D
-J
2 rearranged fragments are shown on
the left side (C).
[View Larger Version of this Image (39K GIF file)]
,
, and
Genes Take Place Normally in IL-7R-deficient Mice.
2 probe (see
Fig. 1 A, middle). The ES cell DNA showed a 4.8-kb germline J
2 fragment. Thymocyte DNA showed decreased intensity of the J
2 germline fragment and smear patterns of
J
2 recombined fragments in both IL-7R +/
and
/
mice. Quantification revealed that 81% and 69% of J
2 alleles are rearranged in IL-7R +/
and
/
thymus, respectively. Thus, the frequency of J
2 rearrangement is
slightly decreased in IL-7R
/
mice compared with
IL-7R +/
mice. Next, we hybridized a Southern blot
with J
1 and J
1 probes (see Fig. 1 B). A 6.8-kb J
1 and a
7.7-kb J
1 germline fragment was detected in ES cell
DNA. These were greatly reduced in the thymus because
of deletion of the
locus by V
-J
recombination in
T cells. Extra faint fragments and a smear pattern of J
recombined fragments were detected in IL-7R
/
mice as
well as in IL-7R +/
mice. Thymocyte DNA from IL-7R
/
mice showed several V
-D
-J
and D
-J
recombined fragments at the comparable intensity with that from
IL-7R +/
mice.
genes was further examined by PCR with V
1, V
4, V
5, and J
1 primers. In contrast with TCR
genes, the signals of V
1-D
-J
1, V
4-
D
-J
4, and V
5-D
-J
1 fragments were only slightly
diminished (two- to eightfold reduction) in IL-7R
/
mice relative to IL-7R +/
mice (Fig. 2 B). Because IL-7R
/
thymus lacks
T cells (12), the V
-J
recombined fragments are probably derived from
T cells
and precursor cells. Thus, the difference in the amounts of
TCR
products may be attributed to the presence and
absence of
T cells in the thymus of IL-7R +/
and
/
mice, respectively. Collectively, TCR
gene rearrangement seems not to be severely hampered in the IL-7R-deficient
mice, supporting the data of Southern blot analysis.
8.2, D
2, and J
2
primers revealed six D
-J
and six V
-J
recombined
fragments in both the IL-7R +/
and
/
thymus DNA
(Fig. 2 C). These results demonstrate that IL-7R is not essential for both D
-J
and V
-D
-J
recombinations. It
is recently reported that IL-7 supported D
to J
rearrangements but not V
to D
J
rearrangement in fetal
thymic organ culture of fetal liver precursor cells (26).
However, our results do not support the notion that IL-7
may play some specific role on D
-J
recombination. All
these results suggested that the rearrangements of TCR
,
, and
genes take place normally in IL-7R-deficient mice.
and
/
mice by PCR with RAG-1, RAG-2, TdT, and Ku-80 primers, and hybridized with each cDNA probes (Fig. 3).
The levels of RAG-1, RAG-2, TdT, and Ku-80 transcripts
in IL-7R
/
mice were almost comparable to those of
IL-7R +/
mice. These results suggest that the mutation
of IL-7R did not inhibit the expression of RAG-1, RAG-2,
TdT, and Ku-80 genes.
Fig. 3.
Expression of V-(D)-J
recombination-associating genes
in the thymus of the IL-7R-deficient mice. cDNA prepared from
4-wk-old adult thymocytes was
amplified by PCR using RAG-1,
RAG-2, TdT, Ku-80, and HPRT
primers, and the Southern blots of
PCR products were hybridized
with each probe.
[View Larger Version of this Image (64K GIF file)]
genes are frequently recombined in
T cells
(28). More than 70% of V
1.2 and V
2 alleles are recombined in total thymocytes. In this study, we used this phenomenon to examine whether TCR
recombination is
blocked in
T cell precursors of IL-7R-deficient mice.
IL-7R-deficient mice had no detectable TCR
recombination by Southern blot analysis. Furthermore, the recombination of all the V
genes was undetectable in fetal and adult thymi by PCR analysis. Thus, we demonstrated that
the signal from IL-7R is indispensable for the V-J recombination of TCR
genes in
T cell precursors. And it is
highly possible that the TCR
recombination is also
blocked in
T cell precursors as well as in
T cell precursors. This would be certainly one reason why IL-7Rdeficient mice lack
T cells.
genes. The recombination of TCR
,
, and
genes are not affected. In
addition, the recombination of IgH and L chain genes is
probably not hampered by the mutation, because the IL-7Rdeficient mice have decreased but certain numbers of surface IgM+ B cells in the periphery (12). Second, the recombination of all the V
genes is blocked. In a previous
report, IL-7 induced the rearrangement of V
2 and V
4,
but not V
3 or V
5 genes in fetal thymic organ culture of
fetal liver precursors (2). In contrast, not only V
2 and V
4
but also all the other V
genes in the TCR
1,
2, and
4
clusters are hampered to recombine in the mutant mice.
Third, TCR
gene recombination is blocked not only in
but also in
T cell precursors. These features suggest the presence of highly specific regulation for TCR
gene
rearrangement.
recombination in the IL-7R-deficient mice, one possibility can be
considered. It is to suppose that the TCR
locus may contain a specific cis-control element(s). One possible candidate
for this element is TCR
enhancers. Recently, it was reported that IL-7 induces the phosphorylation and DNA
binding activity of Stat5 protein in T cells (29). Because each TCR
enhancer contains a Stat5 binding sequence
(30, 31), Stat5 may play a role on the regulation of TCR
recombination. It is also possible that some unknown factor(s) other than Stat5 may specifically regulate the recombination of TCR
locus.
Address correspondence to Koichi Ikuta, Department of Medical Chemistry, Faculty of Medicine, Kyoto University, Yoshida, Sakyo-ku, Kyoto 606, Japan.
Received for publication 9 August 1996
This work was supported by a grant-in-aid from the Ministry of Education, Science, and Culture of Japan, and by the grant provided by the Ichiro Kanehara Foundation.We thank Drs. Y. Takagaki, H. Yamagishi, O. Koiwai, and Y. Hashimoto for probes and discussion; Ms. M. Sugimori and M. Iidaka for technical assistance; Dr. S. Takeda for critically reading the manuscript; and Drs. M. Fujiwara and T. Honjo for encouragement.
1. |
Muegge, K.,
M.P. Vila, and
S.K. Durum.
1993.
Interleukin-7:
a cofactor for V(D)J rearrangement of the T cell receptor ![]() |
2. |
Appasamy, P.M.,
T.J. Kenniston,
Y. Weng,
E.C. Holt,
J. Kost, and
W.H. Chambers.
1993.
Interleukin-7-induced expression of specific T cell receptor ![]() |
3. | Grabstein, K.H., T.J. Waldschmidt, F.D. Finkelman, B.W. Hess, A.R. Alpert, N.E. Boiani, A.E. Namen, and P.J. Morrissey. 1993. Inhibition of murine B and T lymphopoiesis in vivo by an anti-interleukin-7 monoclonal antibody. J. Exp. Med. 178: 257-264 [Abstract] . |
4. | Sudo, T., S. Nishikawa, N. Ohno, N. Akiyama, M. Tamakoshi, H. Yoshida, and S. Nishikawa. 1993. Expression and function of the interleukin-7 receptor in murine lymphocytes. Proc. Natl. Acad. Sci. USA. 90: 9125-9129 [Abstract] . |
5. | von Freeden-Jeffry, U., P. Vieira, L.A. Lucian, T. McNeil, S.E. Burdach, and R. Murray. 1995. Lymphopenia in interleukin (IL)-7 gene-deleted mice identifies IL-7 as a nonredundant cytokine. J. Exp. Med. 181: 1519-1526 [Abstract] . |
6. | Peschon, J.J., P.J. Morrissey, K.H. Grabstein, F.J. Ramsdell, E. Maraskovsky, B.C. Gliniak, L.S. Park, S.F. Ziegler, D.E. Williams, C.B. Ware, J.D. Meyer, and B.L. Davison. 1994. Early lymphocyte expansion is severely impaired in interleukin-7 receptor-deficient mice. J. Exp. Med. 180: 1955-1960 [Abstract] . |
7. | Ikuta, K., N. Uchida, J. Friedman, and I.L. Weissman. 1992. Lymphocyte development from stem cells. Annu. Rev. Immunol. 10: 759-783 [Medline] . |
8. | Haas, W., P. Pereira, and S. Tonegawa. 1993. Gamma/delta cells. Annu. Rev. Immunol. 11: 637-685 [Medline] . |
9. |
Watanabe, Y.,
T. Sudo,
N. Minato,
A. Ohnishi, and
Y. Katsura.
1991.
Interleukin 7 preferentially supports the growth of
![]() ![]() |
10. |
Matsue, H.,
P.R. Bergstresser, and
A. Takashima.
1993.
Keratinocyte-derived IL-7 serves as a growth factor for dendritic
epidermal T cells in mice.
J. Immunol.
151:
6012-6019
|
11. | Watanabe, M., Y. Ueno, T. Yajima, Y. Iwao, M. Tsuchiya, H. Ishikawa, S. Aiso, T. Hibi, and H. Ishii. 1995. Interleukin 7 is produced by human intestinal epithelial cells and regulates the proliferation of intestinal mucosal lymphocytes. J. Clin. Invest. 95: 2945-2953 [Medline] . |
12. |
Maki, K.,
S. Sunaga,
Y. Komagata,
Y. Kodaira,
A. Mabuchi,
H. Karasuyama,
K. Yokomuro,
J. Miyazaki, and
K. Ikuta.
1996.
Interleukin-7 receptor-deficient mice lack ![]() ![]() |
13. |
Cao, X.,
E.W. Shores,
L.J. Hu,
M.R. Anver,
B.L. Kelsall,
S.M. Russell,
J. Drago,
M. Noguchi,
A. Grinberg,
E.T. Bloom,
W.E. Paul,
S.I. Katz,
P.E. Love, and
W.J. Leonard.
1995.
Defective lymphoid development in mice lacking expression of the common cytokine receptor ![]() |
14. | Park, S.Y., K. Saijo, T. Takahashi, M. Osawa, H. Arase, N. Hirayama, K. Miyake, H. Nakauchi, T. Shirasawa, and T. Saito. 1995. Developmental defects of lymphoid cells in Jak3 kinase-deficient mice. Immunity. 3: 771-782 [Medline] . |
15. |
Takagaki, Y.,
N. Nakanishi,
I. Ishida,
O. Kanagawa, and
S. Tonegawa.
1989.
T cell receptor-![]() ![]() |
16. |
Winoto, A.,
S. Mjolsness, and
L. Hood.
1985.
Genomic
organization of the genes encoding mouse T-cell receptor
![]() |
17. |
Takeshita, S.,
M. Toda, and
H. Yamagishi.
1989.
Excision
products of the T cell receptor gene support a progressive rearrangement model of the ![]() ![]() |
18. |
Ikuta, K.,
M. Hattori,
K. Wake,
S. Kano,
T. Honjo,
J. Yodoi, and
N. Minato.
1986.
Expression and rearrangement of
the ![]() ![]() ![]() |
19. | Oettinger, M.A., D.G. Schatz, C. Gorka, and D. Baltimore. 1990. RAG-1 and RAG-2, adjacent genes that synergistically activate V(D)J recombination. Science (Wash. DC). 248: 1517-1523 [Medline] . |
20. |
Itohara, S.,
P. Mombaerts,
J. Lafaille,
J. Iacomini,
A. Nelson,
A.R. Clarke,
M.L. Hooper,
A. Farr, and
S. Tonegawa.
1993.
T cell receptor ![]() ![]() ![]() ![]() ![]() |
21. | Palacios, R., and J. Samaridis. 1993. Bone marrow clones representing an intermediate stage of development between hematopoietic stem cells and pro-T-lymphocyte or proB-lymphocyte progenitors. Blood. 81: 1222-1238 [Abstract] . |
22. | Levin, S.D., S.J. Anderson, K.A. Forbush, and R.M. Perlmutter. 1993. A dominant-negative transgene defines a role for p56lck in thymopoiesis. EMBO (Eur. Mol. Biol. Organ.) J. 12: 1671-1680 [Abstract] . |
23. |
Anderson, S.J.,
K.M. Abraham,
T. Nakayama,
A. Singer, and
R.M. Perlmutter.
1992.
Inhibition of T-cell receptor ![]() |
24. | Chomczynski, P., and N. Sacchi. 1987. Single-step method of RNA isolation by acid guanidinium thiocyanate-phenol- chloroform extraction. Anal. Biochem. 162: 156-159 [Medline] . |
25. | Koiwai, O., T. Yokota, T. Kageyama, T. Hirose, S. Yoshida, and K. Arai. 1986. Isolation and characterization of bovine and mouse terminal deoxynucleotidyltransferase cDNAs expressible in mammalian cells. Nucleic Acids Res. 14: 5777-5792 [Abstract] . |
26. |
Tsuda, S.,
S. Rieke,
Y. Hashimoto,
H. Nakauchi, and
Y. Takahama.
1996.
IL-7 supports D-J but not V-DJ rearrangement of TCR-![]() |
27. | Lin, W.C., and S. Desiderio. 1995. V(D)J recombination and the cell cycle. Immunol. Today. 16: 279-289 [Medline] . |
28. |
Heilig, J.S., and
S. Tonegawa.
1987.
T-cell ![]() |
29. | Foxwell, B.M., C. Beadling, D. Guschin, I. Kerr, and D. Cantrell. 1995. Interleukin-7 can induce the activation of Jak 1, Jak 3 and STAT 5 proteins in murine T cells. Eur. J. Immunol. 25: 3041-3046 [Medline] . |
30. |
Vernooij, B.T.,
J.A. Lenstra,
K. Wang, and
L. Hood.
1993.
Organization of the murine T-cell receptor ![]() |
31. | Ihle, J.N.. 1996. STATs: signal transducers and activators of transcription. Cell. 84: 331-334 [Medline] . |