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1 and T3R2 Gene Deletion on T and B Lymphocyte Development1
Ecole Normale Supérieure de Lyon, Laboratoire de Biologie Moléculaire et Cellulaire, Unité Mixte de Recherche 5665 Centre National de la Recherche Scientifique/Ecole Normale Supérieure, Lyon, France
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Abstract |
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and T3Rß genes. There is now accumulating evidence that
thyroid hormones act on the immune system. Indeed, mice deficient for
thyroid hormones show a reduction in lymphocyte production. However,
the mechanisms involved and, in particular, the role of the different
thyroid hormone receptors in lymphocyte development have not been
investigated. To address that question, we have studied lymphocyte
development in mice deficient for the T3R1 and T3R2 gene
products. A strong decrease in spleen cell numbers was found compared
with wild-type littermates, B lymphocytes being more severely affected
than T lymphocytes. A significant decrease in splenic macrophage and
granulocyte numbers was also found. In bone marrow, a reduction in
CD45+/IgM- pro/pre-B cell numbers was found in
these mice compared with wild-type littermates. This decrease seems to
result from a proliferation defect, as
CD45+/IgM- cells incorporate less
5-bromo-2'-deoxyuridine in vivo. To define the origin of the bone
marrow development defect, chimeric animals between
T3R-/- and Rag1-/- mice were generated.
Results indicate that for B cells the control of the population size by
T3R1 and T3R2 is intrinsic. Altogether, these results show that
T3R1 or T3R2 gene products are implicated in the control of the B
cell pool size. |
Introduction |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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The influence of thyroid hormones on the immune system has been extensively studied in mice deficient for hormones of the pituitary/thyroid axis. Snell dwarf (dw/dw) mice are deficient in anterior pituitary hormones, i.e., growth hormone (GH),4 prolactin, and thyroid-stimulating hormone (TSH), due to a point mutation in the gene encoding the Pit-1 transcription factor (5). Lack of GH and TSH production subsequently causes a drop in seric concentrations of insulin-like growth-factor-I (IGF-I) (6) and thyroid hormones, respectively. The numerous studies of the immune system in Snell dwarf mice have revealed a role for thyroid hormones in B and T cell development (7, 8, 9, 10, 11, 12, 13). For example, an increase in thymocyte cellularity is induced by exogenously administered thyroxine (T4) in Snell dwarf mice, and this effect has been confirmed in the thyroid hormone deficient hyt/hyt strain of mice (13) and in normal mice (4). For the B cell lineage, there is a drop in cell numbers at the pro/pre-B cell stage (10, 12, 13), which could result from a proliferation or differentiation defect.
Deficient thyroid hormone production seems the main factor responsible for impaired B cell development in Snell dwarf mice. Indeed, pre-B cell numbers reach normal levels after thyroxine injections, while they are not restored by prolactin, GH, or IGF-I treatment (12, 14). The latter findings are consistent with the observation that B cell development occurs normally in IGF-I, GH, and prolactin-deficient mice (13, 14). The predominant effect of thyroid hormones on B cell development was confirmed by the recovery of the pre-B cell compartment in the hyt/hyt thyroid hormone-deficient mice following T4 injections (13).
In these studies, the target of thyroid hormones was not identified,
i.e., it is still unclear whether they regulate the size of the B cell
pool by acting directly on B cell progenitors or by optimizing the
cellular environment necessary for their development. In addition, the
thyroid hormone receptors that influence lymphoid development have not
been identified. The thyroid gland produces T4
that is metabolized by thyroxine 5'-deiodinases to its active form:
triiodo-thyronine (T3) (15, 16).
T3 binds to several nuclear receptors encoded by
the T3R and T3Rß loci (17, 18). T3R
(19)-, T3Rß (20)-, and T3R1
(21)-deficient mice have recently been generated by
targeted gene disruption. The T3R KO mice are deficient for the
T3R1 and T3R2 isoforms (19). However, they are still
able to express the T3R
1 and T3R2 short transcripts
(22), which function is unknown. These mice have a general
growth defect and die between 4–6 wk of age. A number of defaults,
including bone and small intestine development, have been investigated
(19).
We have studied the development of lymphocytes in these T3R KO mice.
We have found that the size of the mature B cell pool is particularly
affected. This default was at least partly due to a lack of B cell
progenitor proliferation. Finally, we show that intrinsic expression of
T3R1 or T3R2 gene products is needed for the development of a
normal B cell pool.
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Materials and Methods |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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Rag1-/- mice were purchased from
Transgenic Alliance (l’Arbresle, France). T3R KO mice, developed on
the outbred OF1 background, were generated in our
laboratory (19). All mice were bred in the institute’s
animal facility and kept under pathogen-free conditions. As homozygous
T3R KO mice die between 4 and 6 wk of age, heterozygous animals were
routinely crossed to generate the T3R-/- and
T3R+/+ littermates used in the experiments.
The genotype of the offspring was analyzed by PCR, using a mixture of
oligonucleotides specific for T3R (A and B) and a lacZ
oligonucleotide (lacZ-A5) specific for the targeting vector. A PCR
product is amplified with the oligonucleotides A and B when the
wild-type allele is present, and with the oligonucleotides A and
lacZ-A5 when the gene is disrupted (A, 5'-GGACAAGTCTCTGAAGACTTCC-3'; B,
5'-GTCTGACCCACACTCCACCTTG-3'; lacZ A5,
5'-CCTCTTCGCTATTACGCCAGCTGG-3'). The amplification conditions used
were 20 s at each of the following temperatures: 94°C, 58°C,
and 72°C, for 32 cycles.
Fluorescence staining and flow cytometry sorting
For surface marker analysis, spleen cells were stained as
previously described (23). The following Abs were used:
2B8-biotin (anti-CD117 (c-kit)), anti-CD4-PE, and
anti-CD8-Tricolor from Caltag Laboratories (Burlingame, CA);
R6-60.2-biotin (anti-IgM), M1/70-biotin (anti-CD11b/Mac-1),
S7-biotin (anti-CD43), 7D4-FITC (anti-CD25), and RB6-8C5-biotin
(anti-Ly-6G/Gr-1) from Becton Dickinson (Le Pont de Claix, France);
RA3 6B2-PE (anti-B220) from Sigma Immunochemicals (St. Quentin
Fallavier, France); 145.2C11-FITC (anti-CD3) and M1.93-biotin
(anti-CD45) were prepared in house. Avidin-Tricolor (Caltag
Laboratories) was used to reveal biotin-conjugated Abs.
BrdU labeling and staining were performed as previously reported (23). Briefly, mice were injected twice i.p. with 1 mg BrdU (Sigma-Aldrich Chimie, St. Quentin Fallavier, France) at a 30-min interval. Six hours later, animals were sacrificed and the lymphocytes were surface stained. Cells were then fixed and permeabilized, and after partial DNA digestion, BrdU incorporation was revealed by a FITC-conjugated anti-BrdU Ab from Becton Dickinson (Le Pont de Claix, France; clone B44).
Cells were analyzed using the FACScan device (Becton Dickinson, Mountain View, CA) and the CellQuest software (Becton Dickinson Immunocytometry Systems, San Jose, CA). For cell cycle analysis, cells were surface stained and then fixed in 70% cold ethanol. Before analysis, cells were washed in PBS and incubated for 30 min to 2 h in 0.5 µg/ml Hoechst 33342 (Molecular Probes, Leiden, The Netherlands). Cells were analyzed in the presence of the die on a FACStarPlus (Becton Dickinson) equipped with an UV argon laser.
Hormone assays
Cortisol levels in sera were assayed by a private laboratory (Laboratoire d’Analyses Médicales Collombel-Orfeuvre, France) using an enzyme-linked fluorescent assay (ELFA).
Generation of chimeric animals by morulae aggregation
Rag1-/- and
T3R+/- animals were crossed independently. On
2.5 days postcoitum, mice were sacrificed, oviducts were dissected out,
and morulae were isolated. The zona pellucida was removed from morulae
by acid Tyrode’s solution. Morulae from the
Rag1-/- cross were aggregated to the morulae
from the T3R+/-, as previously described
(24). After overnight in vitro expansion, the resulting
blastocysts were transferred to the uteruses of 2.5-day postcoitum
pseudo-pregnant females. For each offspring, the T3R genotype of the
morulae derived from the T3R+/- cross was
determined on mature lymphocytes. Indeed, as mature lymphocytes cannot
be derived from the Rag1-/- morulae, this
cellular subset is not chimeric. The degree of chimerism was estimated
by measuring the ratio between PCR products corresponding to the
wild-type and targeted T3R gene locus, amplified from
hepatocytes.
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Results |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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KO mice show a defect in lymphoid organ cell numbers
To assess the effect of T3R1 and T3R2 deletion on lymphocyte
development, we first determined cell numbers in primary (thymus and
bone marrow) and secondary (spleen) lymphoid organs of T3R KO mice,
at different times following birth. As shown in Fig. 1
, at 10 days of age, cell numbers of
T3R KO mice are not significantly different when compared with
wild-type littermates. In contrast, by day 18 there is a sharp
difference in thymocyte and splenic lymphocyte numbers in T3R KO
compared with wild-type animals, while bone marrow cell numbers remain
equivalent in both types of mice. By day 24, cell numbers in all three
lymphoid organs are drastically reduced in KO mice. This defect is
further increased at later time points (data not shown).
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KO mice also suffer from stress-inducing defects,
including decreased nutritional functions due to a delayed maturation
of the small intestine (19). The stress response
influences the immune system, notably through glucocorticoid
production, which down-regulates immune processes and induces
apoptosis of lymphoid cells (25). In particular, the
percentage of double-positive thymocytes is a good indicator of stress,
as these cells are the most sensitive to glucocorticoid-induced
depletion (26). Hence, to assess stress levels, we have
measured cortisol levels in the blood of mice aged 18 or 32 days. At 18
days of age, there is no significant difference in the levels of
cortisol measured in T3R KO and wild-type mice (28 ± 8 nM vs
21 ± 1 nM). However, by day 32, T3R KO mice show a sharp rise
in their levels of circulating cortisol compared with wild-type mice
(76 ± 25 nM vs 28 ± 12 nM). Moreover, we have found that
the CD4+CD8+
double-positive subset of thymocytes in T3R KO mice is not
significantly affected up to day 24 of age (Fig. 1
), confirming the
absence of major stress-induced modifications of the immune system
during early life in these mice.
Therefore, to study the impact of T3R1 and T3R2 deletion on the
immune system without potential interference of the stress response, we
have performed all further analyses on 17- to 19-day-old animals.
Moreover, in all experiments, the percentage of double-positive
thymocytes was measured, and the few mice (less than 3%) showing a
preferential deletion of double-positive thymocytes, i.e., mice in
which the double-positive subset represented less than 80% of total
thymocytes, were not included in the analysis.
Finally, as T3R KO mice are smaller than wild-type littermates
(19), cellularity in lymphoid organs was normalized by
calculating a cellularity index, which corresponds to the total cell
number divided by the weight of the animal (27).
Splenic B lymphocytes are severely affected by T3R1 and T3R2
deletion
To further characterize splenic subpopulations affected in T3R
KO mice, splenocytes were stained with anti-CD45R (B220), CD3, CD4,
and CD8 Abs. As shown in Fig. 2, both B
and T lymphocyte numbers were decreased in spleens from T3R KO
animals. However, if T lymphocyte cellularity was reproducibly
decreased by about 30% as compared with the control littermates (Table I), the small number of animals analyzed
in each group and the wide variability among them led to a poorly
significant difference between deficient and wild-type animals in each
experiment (0.05 < p < 0.1; Student’s
t test, Fig. 2). It is noteworthy that the numbers of
CD4+ and CD8+ T lymphocytes
were reproducibly reduced to the same extent (data not shown).
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) decreased by about 60% in T3R-deficient mice
compared with wild-type littermates (Fig. 2). Similar results were
obtained when IgM+ splenic cells were measured,
indicating that all B cell subsets were affected in the periphery (data
not shown). Thus, T3R1 and T3R2 gene deletion affects splenic B
cells more profoundly than splenic T lymphocytes.
As shown in Fig. 2, the numbers of splenic granulocytes and
macrophages, identified by anti-Ly-6G (Gr-1+)
and anti-CD11b (Mac-1+) Abs, respectively,
were also significantly reduced by about 50% in T3R-deficient mice
compared with wild-type aged-matched control animals.
T3R1 and T3R2 deletion affects lymphocytes in primary
lymphoid organs
As T3R1 and T3R2 gene deletion affects both B and T
lymphocyte numbers in the periphery, we questioned whether they
developed normally in primary lymphoid organs. As shown in Fig. 3A, the total number of cells
in bone marrow, when corrected for the weights of mice, was not
significantly different in wild-type and T3R KO mice. However, the
numbers and percentages of B lineage (B220+) bone
marrow cells were significantly (Fig. 3A) and reproducibly
(Table II) reduced by about 20% in
T3R-deficient animals. This decrease in the number of B lymphocyte
precursors preferentially affects the pro/pre-B cell
(B220+IgM-) stage (Fig. 3A, Table II). Immature/mature
(B220+IgM+) B cell numbers
were not reproducibly reduced in bone marrow of T3R KO mice (Table II). To further pinpoint the B cell progenitor defect, we have used
anti-CD43, CD25, and CD117 (c-kit) Abs to look at the
different progenitor B cell subsets, as defined by A. Rolink and
colleagues (28). Results in Table III show that only the
B220+CD25+ pre-BII cells
were significantly decreased in T3R KO animals. When cells were
analyzed according to their size, we found that only the small
B220+CD25+ pre-BII cells
were affected (Table III).
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1 and T3R2 gene deletion
reproducibly (Table II) induces a slightly significant (0.025 <
p < 0.05; Student’s t test, Fig. 3B) decrease of about 30% in thymocyte numbers.
Interestingly, thymic subpopulations were equally affected as the
percentages of CD4-CD8-,
CD4+CD8+,
CD4+CD8-, and
CD4-CD8+ thymocytes were
not modified in 17- to 19-day-old T3R KO animals (data not
shown).
Lymphocyte precursors from T3R KO mice proliferate less in
primary lymphoid organs
To determine whether the reduction in lymphocyte numbers in both
primary and secondary lymphoid organs of T3R KO mice was due to a
decreased proliferative capacity of these cells, we have measured their
proliferation in vivo. For that purpose, T3R KO mice and wild-type
littermates were injected twice i.p. at a 30-min interval with 1 mg
BrdU. This thymidine analogue is incorporated in the DNA of
cycling cells. Incorporation of BrdU in bone marrow and thymic cells
was measured 6 h after the last injection. Cells were first
stained for surface markers to identify lymphocyte subsets.
BrdU+ cells were then revealed by a
FITC-conjugated anti-BrdU Ab, as described in Materials and
Methods. PBS-injected animals were used as a negative control for
background staining.
As shown in Fig. 4A and Table IV, the proportion of bone marrow
B220+ cycling cells is decreased by 40% in
T3R KO mice. When looking at bone marrow subpopulations, as expected
(29, 30), most of the cycling B lymphocyte precursors were
contained in the pro/pre-B cell subset (Table IV).
However, in T3R KO animals, the percentage of
BrdU+ cells was decreased in both the pro/pre-B
cell (B220+IgM-) and the
immature/mature B cell
(B220+IgM+) subset by 30%
and 50%, respectively, compared with wild-type controls.
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KO mice, a small (15%) but significant
(p 
0.05) reduction in the percentage of
cycling cells was observed among all B cell progenitor subsets defined
by these markers (Fig. 5, data not
shown). Thus, T3R1 and T3R2 gene deletion affects the
proliferation of all subsets of progenitor B cells. This effect was
particularly obvious in large
B220+CD25+ pre-BII cells,
which represent the major subset of cycling cells (28)
(Fig. 5B). This reduced proliferation might explain the
defect in the number of small
B220+CD25+ pre-BII cells
observed in T3R KO mice.
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KO mice also proliferate less in vivo than
thymocytes from wild-type animals. Under the experimental conditions,
using BrdU, the percentage of cycling thymocytes is decreased by about
20% (Fig. 4B).
T3R1 or T3R2 gene products control the size of the B cell
pool by intrinsic mechanisms
As T3R1 and T3R2 are widely expressed among murine
tissues (19, 31, 32), we questioned whether the deficient
lymphocyte development was intrinsic to these cells or whether it was
due to a defect in environmental factors. To address this question, we
produced T3R-/- x
Rag1-/- chimeric animals.
T3R+/- mice were crossed and the resulting
morulae were aggregated to morulae from Rag1-deficient mice. Rag1 is
necessary for TCR and Ig gene recombination (33), and mice
deficient for this enzyme are not able to develop mature T or B
lymphocytes (34). Thus, in T3R x
Rag1-/- chimera, all mature B and T lymphocytes
can only derive from the T3R morulae, while all other cell types are
a mix of cells derived from T3R or Rag1-/-
morulae. The degree of chimerism was analyzed by PCR analysis on liver
cells, as described in Materials and Methods. For the
experiment described, it was estimated that
Rag1-/- T3R-/-
chimeric animals contained about 60% to 75% of liver cells from
Rag1-/- (i.e., T3R+/+
genotype) origin. This implies that in
T3R-/- x Rag1-/-
chimeric animals, mature lymphocytes that do not ex-press T3R1 and
T3R2 have developed in a cellular environment in which a significant
proportion of cells express these proteins. Hence, any decrease in
lymphocyte cell numbers generated in these chimeric mice would indicate
an intrinsic involvement of T3R1 or T3R2 gene products in the
control of the development of these cells.
As shown in Fig. 6B, there is
no significant difference in thymocyte numbers between
T3R-/- x Rag1-/-
and T3R+/+ x Rag1-/-
mice. In contrast, splenic cellular indices are significantly reduced
by about 55% in T3R-/- x
Rag1-/- mice compared with the
T3R+/+ x Rag1-/-
control chimera. This decrease results mainly from a strong reduction
in splenic B cell numbers (Fig. 6A). Indeed, splenic T
cells, granulocytes, and macrophages are found in equivalent numbers in
T3R-/- x Rag1-/-
and T3R+/+ x Rag1-/-
mice. This indicates that the defect in T cell numbers observed in
T3R KO mice was not intrinsic to T3R-/- T
cells and, more importantly, that the cellular environment provided in
chimeric animals was able to support T lymphocyte, granulocyte, and
macrophage development. Thus, these results indicate that B cells, in
contrast to T cells, are direct targets for thyroid hormone regulation
through the T3R receptor.
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Discussion |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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KO mice
The aim of this study was to determine the role of T3R receptor
isoforms in the immune system. Mice deficient for T3R1 and T3R2
isoforms show a reduced T and B lymphocyte development that results in
a decreased cellularity. However, lymphocyte development seems
qualitatively normal, as no difference was observed in terms of surface
phenotype and function. Indeed, in vitro, spleen lymphocytes from
T3R KO mice show a normal proliferative response following LPS or
anti-CD3 activation (data not shown). Furthermore, we show that
T3R1 and T3R2 gene products are involved in the proliferation
control of progenitor cells in primary lymphoid organs. This does not
exclude a role for these proteins in the differentiation of the T or B
lymphocyte precursor cells. The reduced lymphocyte cellularity observed
in T3R KO mice could also result from an increased sensibility to
programmed cell death (35). This does not seem to be the
case, at least for bone marrow cells, as we did not find
sub-G1 apoptotic cells following Hoechst cell
cycle analyses on freshly isolated bone marrow cells. Similarly, no
detectable increase in apoptosis after in vitro bone marrow cell
culture was found (data not shown).
Multiple levels of T3 actions on the immune system development
Previous observations in Snell dwarf mice strongly supported a
direct effect of T3 on B cell development, but
they could not completely exclude a possible indirect effect on
GH/IGF-I production by the cellular environment. Indeed, thyroid
hormones regulate GH/IGF-I production by enhancing GH gene
transcription in a pituitary cell line (36). Furthermore,
IGF-I has been shown to promote B lymphopoiesis (37, 38).
Our results show that T3 seems to act directly on
B lymphocytes. This could be explained by the direct control by T3R1
or T3R2 of genes involved in B cell progenitor proliferation and/or
differentiation. Indeed, it has been shown that bone marrow-derived B
lineage cell lines express these isoform of the
T3 nuclear receptors (39). Still,
one cannot exclude that T3 acts only to
up-regulate GH/IGF-1 secretion by B lineage cells (40, 41). However, this seems unlikely, as it has been shown that GH
is unable to fully restore the pre-B cell compartment in Snell dwarf
mice (12).
Conversely, defective T cell development in T3R KO mice was shown to
depend only on cellular environment, as it is fully restored in
T3R-/- x Rag1-/-
chimeric animals. This is in accordance with previous reports showing
that thymic cellularity is enhanced by treatment with IGF-I
(42) or GH (11, 43). Furthermore, these
hormones are locally produced in the thymus (25, 44).
T3 could also influence thymocyte development
through the regulation of other thymic-origin hormonal factors, such as
thymulin (Zn-FTS), which induces thymocyte proliferation and
differentiation (45). Indeed, the production of thymulin
is correlated to seric concentrations of T3 and
T4 (46, 47). However, T3R1 or
T3R2 expression seems to influence the immune system development at
multiple levels, as it acts directly on B lymphocytes and through the
cellular environment on T lymphocytes.
In the case of myeloid cell development, we have found a deficit in
macrophage (Mac-1+) and granulocyte
(Gr-1+) splenic cell numbers in T3R KO mice.
However, T3 again seems to act at another level,
as it is unlikely that a defective myeloid central development accounts
for this decreased macrophage and granulocyte splenic cellularity.
Indeed, we did not observe any significant differences in the number of
Gr-1+ and Mac-1+ bone
marrow myeloid precursors (data not shown), as previously reported in
Snell dwarf mice (12). As myeloid cells do not need Rag1
enzyme expression during their development, our experiments with
chimeric animals did not allow us to identify the thyroid hormone
target. However, a direct effect of T3 on
macrophages and granulocytes has been reported in a number of systems.
Indeed, thyroid hormones modulate the metabolism and the functions of
purified rat macrophages (48, 49) and stimulate
phagocytosis by purified human polymorphonuclear granulocytes
(50). Moreover, the production of TSH by cultured
monocytes following thyrotropin-releasing factor stimulation is
inhibited by T3 (51).
The role of the different isoforms in the immune system development
The immune deficiencies observed in T3R KO mice are directly
attributable to the absence of the T3R1 and T3R2 gene products.
Gene transcriptional regulation by T3 nuclear
receptor isoforms is complex. The first degree of complexity is given
by the numerous isoforms of T3 nuclear receptors,
some of which do not bind T3 nor act as
transcription factors. Furthermore, these isoforms act as homodimers or
heterodimers together with other members of the nuclear receptor family
(52, 53) and, depending on the targeted genes and the
presence of their ligand, coactivators or corepressors either activate
or repress gene transcription (17, 53, 54, 55).
T3 nuclear receptor isoforms can also inhibit one
another’s transcriptional activities (22, 56). Finally,
T3R isoforms specifically retro-control thyroid hormone production in a
complex fashion. Indeed, although thyroid hormones negatively
retro-control pituitary TSH production, T3Rß-deficient mice have
elevated seric levels of T3 and
T4, together with high TSH serum concentrations
(20, 57), while the level of all three hormones is reduced
after 3–4 wk of age in T3R KO mice compared with wild-type
littermates. (19). In T3R1-deficient mice
(21), seric T3 is unaffected, while
T4 seric concentrations are reduced only in male
animals. It is important to note that in our experiments using 17- to
19-day-old animals, T3 and
T4 seric concentrations were always found in the
normal range, definitely establishing a specific role for T3R1 and
T3R2 gene deletion in the observed phenotype.
Given the complexity of the regulation of gene transcription by nuclear
hormone receptors, it would be of particular interest to correlate the
hormonal status and immune deficiencies in different mice deficient for
T3R isoforms and other members of the nuclear receptor family. We have
preliminary data showing a decreased granulocyte, macrophage, and T and
B lymphocyte cellularity in spleens from T3Rß KO mice (data not
shown). Our preliminary experiments also show drastically reduced
numbers of these cells in the spleens of mice deficient for all T3R
isoforms, indicating an additive effect of T3R and T3Rß gene
deletions (data not shown). This further supports a role for
T3 in B lymphocyte development and suggests a
partial redundancy between thyroid hormone and ß receptors. It
has also been shown that T3R plays a major role in the control of
the proliferation of the crypt cells in the intestine, and that partial
redundancy between T3R and T3Rß also occurs in this system
(58). Moreover, additive effect of T3R and T3Rß gene
deletions excludes the possibility that in absence of T3R1,
T3 would act through T3Rß to reduce cell cycle
progression. Indeed, it has been shown that thyroid hormones regulate
proliferation arrest and differentiation of oligodendrocyte precursor
cells and that the level of T3Rß1 receptor expression in these cells
is involved in determining the time when they will withdraw from cell
cycle and differentiate (59).
In conclusion, this study shows that T3R1 and T3R2 gene products
are involved in immune system development. It also shows for the first
time that expression of these receptors in bone marrow B lineage cells
is intrinsically needed for a proper B lymphopoiesis. Finally, it
supports increasing amounts of data demonstrating the importance of
cross-talks between neuro/endocrine and immune systems. In terms of
functional consequences of these receptors’ defect, we have found that
T3R-deficient lymphocytes proliferate after polyclonal activation
(data not shown), but we have not been able to test Ag-specific
responses in T3R KO mice that die within a few weeks after birth.
However, this needs to be investigated in the different thyroid
hormone-deficient mice. Indeed, in humans with thyroid hormone
resistance due to mutations in T3Rß receptors, a cohort study showed
a high frequency of nose, ear, and throat infections, which could
indicate a partial impairment of their immune system
(60).
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Acknowledgments |
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KO mice breeding, and
genetic analyses. We also thank Dr. K. Dorshkind for critical
reading of the manuscript. |
Footnotes |
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2 C.A. and M.P. equally contributed to the work and should be considered as first authors.
3 Address correspondence and reprint requests to Drs. J. Marvel or O. Chassande, Ecole Normale Supérieure de Lyon, Laboratoire de Biologie Moléculaire et Cellulaire, UMR5665 Centre National de la Recherche Scientifique/Ecole Normale Supérieur, 46, allée d’Italie, 69364 Lyon Cedex 07, France. E-mail addresses:
4 Abbreviations used in this paper: GH, growth hormone; BrdU, 5-bromo-2'-deoxyuridine; IGF, insulin-like growth factor; KO, knockout; T3, triiodo-thyronine; T4, thyroxine; TSH, thyroid-stimulating hormone.
Received for publication April 2, 1999. Accepted for publication October 19, 1999.
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References |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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  L. Quignodon, S. Vincent, H. Winter, J. Samarut, and F. Flamant A Point Mutation in the Activation Function 2 Domain of Thyroid Hormone Receptor {alpha}1 Expressed after CRE-Mediated Recombination Partially Recapitulates Hypothyroidism Mol. Endocrinol., October 1, 2007; 21(10): 2350 - 2360. [Abstract] [Full Text] [PDF]
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 J. R. Klein The immune system as a regulator of thyroid hormone activity. Experimental Biology and Medicine, March 1, 2006; 231(3): 229 - 236. [Abstract] [Full Text] [PDF]
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 C. Angelin-Duclos, C. Domenget, A. Kolbus, H. Beug, P. Jurdic, and J. Samarut Thyroid hormone T3 acting through the thyroid hormone {alpha} receptor is necessary for implementation of erythropoiesis in the neonatal spleen environment in the mouse Development, March 1, 2005; 132(5): 925 - 934. [Abstract] [Full Text] [PDF]
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F. Flamant, A.-L. Poguet, M. Plateroti, O. Chassande, K. Gauthier, N. Streichenberger, A. Mansouri, and J. Samarut Congenital Hypothyroid Pax8-/- Mutant Mice Can Be Rescued by Inactivating the TR{alpha} Gene Mol. Endocrinol., January 1, 2002; 16(1): 24 - 32. [Abstract] [Full Text] [PDF]
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 K. Gauthier, M. Plateroti, C. B. Harvey, G. R. Williams, R. E. Weiss, S. Refetoff, J. F. Willott, V. Sundin, J.-P. Roux, L. Malaval, et al. Genetic Analysis Reveals Different Functions for the Products of the Thyroid Hormone Receptor {alpha} Locus Mol. Cell. Biol., July 15, 2001; 21(14): 4748 - 4760. [Abstract] [Full Text] [PDF]
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 F. R. S. Lima, A. Gervais, C. Colin, M. Izembart, V. M. Neto, and M. Mallat Regulation of Microglial Development: A Novel Role for Thyroid Hormone J. Neurosci., March 15, 2001; 21(6): 2028 - 2038. [Abstract] [Full Text] [PDF]
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G. R. Williams Cloning and Characterization of Two Novel Thyroid Hormone Receptor beta Isoforms Mol. Cell. Biol., November 15, 2000; 20(22): 8329 - 8342. [Abstract] [Full Text]
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 K. Dorshkind and N. D. Horseman The Roles of Prolactin, Growth Hormone, Insulin-Like Growth Factor-I, and Thyroid Hormones in Lymphocyte Development and Function: Insights from Genetic Models of Hormone and Hormone Receptor Deficiency Endocr. Rev., June 1, 2000; 21(3): 292 - 312. [Abstract] [Full Text]
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) and
wild-type (
) mice are shown. Inset, An example of
double anti-CD4/anti-CD8 staining of thymocytes from 18-day-old
T3R
