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-Induced MHC Class II Expression in Mice Lacking Class II Transactivator Due to Targeted Deletion of the GTP-Binding Domain1
*
Lineberger Comprehensive Cancer Center, and Departments of
Microbiology-Immunology and
Medicine, University of North Carolina, Chapel Hill, NC 27599; and
§
Department of Surgery, Duke University, Durham, NC 27710
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Abstract |
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 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
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. These findings demonstrate a requirement for CIITA in
IFN--, IL-4-, and endotoxin-induced MHC class II expression as well
as the possibility of rare CIITA-independent MHC class II
expression. |
Introduction |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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The presentation of antigenic peptides to CD4+ T cells by MHC class II molecules requires the coexpression of invariant chain (Ii)5 and DM in humans or H2-M in mice. In the endoplasmic reticulum, newly synthesized MHC class II molecules associate with Ii and form nonameric complexes consisting of three MHC class II dimers and an Ii trimer (reviewed in Ref. 1). The targeting signal in Ii shuttles these complexes through the Golgi apparatus to a specialized endosomal/lysosomal compartment where class II-associated invariant chain peptide (CLIP) is replaced by a foreign antigenic peptide. The DM molecule plays a critical role in the removal of CLIP and the loading of foreign peptides (2, 3, 4, 5, 6, 7). Peptide-loaded MHC class II complexes subsequently move to the cell surface to present peptides to CD4+ T cells.
Unlike MHC class I molecules, which are expressed by all cell types,
the expression of MHC class II molecules in mice is restricted to B
cells, professional APCs, and thymic epithelial cells (8, 9). In most cell types, except B cells, the expression of MHC
class II molecules is inducible by IFN-. This complex pattern of MHC
class II gene expression is regulated by a number of transcription
factors, including the transcriptional coactivator class II
transactivator (CIITA). CIITA, which was first isolated by
complementation cloning of the MHC class II-defective cell line
RJ2.2.5, restores MHC class II expression in cells of the bare
lymphocyte syndrome complementation group A (10). CIITA is
expressed only in cells that express MHC class II molecules and is the
IFN- inducible trans-acting factor required for the
induction of MHC class II gene expression (11, 12, 13). CIITA
is also necessary for expression of the other IFN- inducible genes
involved in Ag presentation, namely DM and Ii (11, 14, 15, 16). Promoter analyses of the DM, Ii, and MHC class II genes
have revealed the presence of several shared cis-acting
regulatory elements known as the W, X, and Y motifs; however, CIITA
does not appear to bind directly to these promoter sequences.
Structure function analyses of CIITA have been performed to understand the mode of action of CIITA. These analyses revealed that a conventional acidic domain consisting of residues 26–137 (17, 18) and a proline/serine/threonine-rich domain consisting of residues 163–322 are important for transcriptional activities (19). Intriguingly, a GTP-binding consensus sequence contained in residues 421–561 is also important for CIITA function (19, 20). The involvement of acidic and proline/serine/threonine-rich domains in transcriptional activation has been observed for several transcription factors (21, 22, 23, 24, 25); however, a role for a GTP-binding domain in transcriptional activation has not been described previously. The GTP-binding sequence is typically important in signal transduction, protein synthesis, and intracellular protein transport. To further assess the functional role of the GTP-binding domain of CIITA in vivo, we targeted a region of the CIITA gene that spans the GTP-binding domain for removal by homologous recombination. This study reports the production and characterization of such a knockout (KO) mouse strain and demonstrates that CIITA is critical for constitutive as well as inducible expression of MHC class II by a variety of biologic effector molecules. However, a very low level of MHC class II mRNA is still detectable by RT-PCR. This finding is in agreement with a recent report indicating that low levels of class II are still detected on dendritic cells from CIITA null mice (26).
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Materials and Methods |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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Mouse CIITA genomic clones were isolated from a 129/Sv library
(Stratagene, La Jolla, CA) and mapped using restriction enzymes and
human CIITA cDNA probes (19). The targeting vector was
constructed by replacing a 3.0-kb HindIII fragment
containing the GTP-binding domain of CIITA with a neomycin
(neo) gene cassette in plasmid pPNT (27), which
contains the HSV thymidine kinase gene (Fig. 1
A). The targeting vector was
linearized with NotI and electroporated into E14TG2a
embryonic stem (ES) cells. The cells were placed under double selection
with G418 and ganciclovir to enrich for those that had undergone
homologous recombination. Clones were subjected to Southern blot
analysis using a 1.2-kb KpnI CIITA gene fragment as the
probe. Of the 127 clones screened, 3 carried the GTP-binding domain
deletion. These were identified by the presence of a 7-kb hybridizing
mutant band in addition to the 12-kb wild-type (WT) band that was seen
in nontargeted cells (Fig. 1B). Targeted ES cell clones were
injected into C57BL/6 blastocysts, the resulting embryos were implanted
into foster mothers, and these embryos subsequently gave rise to 18
chimeric mice. The male chimeras were mated to 6-wk-old female C57BL/6
mice obtained from The Jackson Laboratory (Bar Harbor, ME). Offspring
carrying the targeted CIITA gene were identified by Southern blot
analysis of tail DNA, which was prepared as described previously
(28). Male and female heterozygotes were intercrossed to
produce the deletion mutant (hereafter designated as
CIITA-/-). All mice were propagated at the
University of North Carolina Animal Facility (approved by the
Institutional Animal Care and Use Committee) and were maintained in a
pathogen-free colony.
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Thymus, spleen, and lymph node (LN) RNAs were isolated from 5- to 6-wk-old mice using Trizol reagent (Molecular Research Center, Cincinnati, OH) according to the manufacturer’s protocol. For Northern blot analyses, total RNA was electrophoresed in a 1% formaldehyde agarose gel, transferred to Nytran membranes (Schleicher and Schuell, Keene, NH), and hybridized with random-primed genomic or cDNA probes according to the manufacturer’s protocol (Schleicher and Schuell). The probes used were: human ß-actin as a control, pI-Aß2 for MHC class II (a gift of Carolyn Doyle, Duke University, Durham, NC), pmIip34 for Ii (a gift of Ron Germain, National Institutes of Health, Bethesda, MD), and pH-2IIa for MHC class I (a gift of Sherman Weissman, Yale University, New Haven, CT). For RT-PCR, first-strand cDNA was synthesized using reverse transcriptase (Life Technologies, Grand Island, NY); PCR was performed using AmpliTaq DNA polymerase (Perkin-Elmer, Norwalk, CT) in a Perkin-Elmer 9600 thermocycler. PCR conditions were: predenaturation at 94°C for 20 s, followed by 30 cycles of denaturation at 94°C for 20 s, annealing at 70°C for 20 s, and elongation at 72°C for 30 s. The primers used were: H-2Aa, 5'-TATGTGGACTTGGATAAGAAG-3' (sense), 5'-ACAAAGCAGATAAGGGTGTTG-3' (antisense); H-2Dd, 5'-CCCTGACCTGGCAGTTGAATG-3' (sense), 5'-AGCTCCAAGGATGACCACAGC-3' (antisense); mouse ß-actin, 5'-GGCATTGTTACCAACTGGGAC-3' (sense), 5'-ACCAGAGGCATACAGGGACAG-3' (antisense); mouse Ii, 5'-GTGTCTGTTTCATCGTCCCAG-3' (sense), 5'-AAGGCAGCAAATGTGTCCAGC-3' (antisense); mouse CIITA, 5'-TGCAGGCGACCAGGAGAGACA-3' (sense), 5'-GAAGCTGGGCACCTCAAAGAT-3' (antisense); and CIITA-5', 5'-GCAGCTACCTGGAACTCCTTA-3' (sense), 5'-CTCATTTACACGGGAGGTCAG-3' (antisense).
Flow cytometric analyses
Cells from the thymus and spleen were dispersed in ice-cold PBS
supplemented with 2% FBS (PBS-FBS). Spleen erythrocytes were lysed by
hypotonic shock. Splenic cells were incubated with rat anti-mouse
CD16/CD32 FcIII/IIR Fc Block (PharMingen, San Diego, CA) at 4°C
for 15 min to block Fc receptors before staining. The cells were
resuspended at 1 x 108 cells/ml in PBS-FBS. A
total of 10 µl of the cell suspension was incubated with Abs on ice
for 30 min in a final volume of 100 µl. Cells that were incubated
with biotinylated Abs were washed three times with PBS-FBS and
subsequently stained with FITC or PE avidin D (Vector Laboratories,
Burlingame, CA) on ice for 30 min. The stained cells were fixed in 2%
paraformaldehyde and analyzed by FACScan (Becton Dickinson, Mountain
View, CA). The Abs used were: biotinylated
anti-H-2Kb/H-2Db for
MHC class I,
anti-I-Ab/I-Eb-FITC for
MHC class II, anti-CD45R/B220-PE for B cells, anti-CD4-FITC for
CD4+ T cells, anti-CD8-PE for
CD8+ T cells, and biotinylated anti-CD11b for
Mac-1. All Abs were purchased from PharMingen.
Fluorescent immunohistology
Thymus, LN, and splenic tissues were snap-frozen in liquid nitrogen for cryostat sectioning. Sections (4–5 µm thick) were air dried and fixed in acetone for 1 min. Before staining, sections were rehydrated in 1x PBS and subsequently incubated with primary Abs. The primary Abs (all purchased from American Type Culture Collection, Manassas, VA) used in this study were: GK1.5 for CD4 staining, Lyt2.2 for CD8 staining, M5/114.15.2 for MHC class II, and M1/42.3.9.8.HLK for MHC class I. The primary Abs were incubated for 30 min at room temperature followed by incubation with affinity-isolated, FITC-conjugated goat anti-rat IgG for 1 h at room temperature. IgG2b was used as an isotype control for MHC class II.
Serum IgM and IgG levels
Serum was isolated from blood using serum separators (Microtainer, Becton Dickinson) according to the manufacturer’s protocol. For ELISA, 100 µl of anti-mouse IgM or IgG (Sigma, St. Louis, MO) at 30 µg/ml were plated and incubated for 2 h at room temperature. The plate was washed three times with 200 µl of PBS/well and blocked overnight with 1% BSA (BSA/PBS) at 4°C. The plate was washed again as described and incubated with 100 µl of the diluted samples for 3 h at room temperature; the sample sera were diluted 1/100, 1/250, 1/500, 1/750, and 1/1000 with 0.02% BSA/PBS. The plate was washed, and alkaline phosphatase-conjugated anti-mouse IgG or anti-mouse IgM (Sigma) was added to the wells and incubated for 1 h at room temperature. After a final wash, 100 µl of phosphatase substrate (Sigma) was added to the wells; the OD results were read at 405 nm.
IL-4, LPS, and IFN- injections
An established protocol was used to demonstrate the IL-4
induction of MHC class II expression (29). Briefly, 6- to
8-wk-old mice were injected i.v. with 2 µg of IL-4 (Endogen, Woburn,
MA) and 5 µg of anti-IL-4 Ab 11B11 (PharMingen) or with normal
saline as a control. Anti-IL-4 Ab was added because of its potentiating
effects on IL-4-induced class II expression, as documented previously
(29). Mice were sacrificed after 48 h, and
single-cell suspensions were prepared from spleens and LNs. Cells were
stained with
anti-I-Ab/I-Eb-FITC and
anti-CD45R/B220-PE or with biotinylated anti-CD11b and
subjected to flow cytometric analyses as described above. LPS and
IFN- (Genzyme, Cambridge, MA) were injected i.p. at doses of 400
µg and 50,000 U, respectively. Again, spleen and LNs were harvested
48 h later, and cells were stained with
anti-I-Ab/I-Eb-FITC and
anti-CD45R/B220-PE or with biotinylated anti-CD11b and
subjected to flow cytometric analyses.
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Results |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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The GTP-binding motifs in CIITA (amino acids 421–561) consist of
the phosphate-binding, Mg2+-binding, and
guanine-binding motifs (19). Mutation of any of these
motifs greatly diminishes the ability of CIITA to
trans-activate the MHC class II promoter (19, 20). To further assess the in vivo function of the GTP-binding
domain of CIITA, a 3.0-kb HindIII fragment containing the
GTP-binding domain of CIITA was replaced by a neomycin (neo)
gene cassette to generate a mouse lacking the GTP-binding domain
(CIITA-/-) (Fig. 1
, A and
B, also see Materials and Methods). Spleen,
thymus, and LN RNAs were isolated from WT control mice and
CIITA-/- mice and examined for CIITA gene
expression by RT-PCR (Fig. 2). The use of
PCR was necessary because endogenous CIITA levels are extremely low.
The use of serially diluted cDNA in PCRs permits the semiquantitative
comparison of two samples in the range where cDNA is not in excess.
These experiments were repeated in three mice with identical results.
In the WT control mice, CIITA expression was detected in the spleen,
thymus (albeit to a lesser extent), and LNs. CIITA expression was not
detected in these same cells isolated from the
CIITA-/- mice using either oligonucleotides
specific for the GTP-binding domain or for the acidic domain (Fig. 2, A and B). The acidic domain lies upstream of the
targeted region.
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To assess whether the CIITA-/- phenotype
affected MHC class II expression, cDNAs prepared from WT and
CIITA-/- mice were examined for MHC class II
and Ii gene expression by RT-PCR. As shown in Fig. 3A, the expression of MHC
class II was greatly reduced in the spleen, thymus, and LNs of the
CIITA-/- mice compared with that of the WT
controls, although the signal was not completely eliminated. The Ii
transcript was also reduced, although to a lesser extent than MHC class
II. There was no significant or consistent difference in MHC class I or
ß-actin gene expression in these mice. Northern blot analyses were
also performed using total RNA isolated from the spleen, thymus, and
LNs to verify the RT-PCR results. According to this assay, the Ii RNA
was markedly reduced and MHC class II RNA was not visible; however,
there were no changes in MHC class I and ß-actin RNA levels in the
CIITA-/- mice compared with the control mice
(Fig. 3B). The differences in gene expression between WT and
CIITA-/- mice were more clearly revealed by
Northern blot analyses than by PCR. This is expected, as PCR is likely
to amplify minor signals, thus mitigating some of the actual
differences between the WT and gene KO mice. Regardless, it is clear
from both types of analyses that the targeted deletion results in a
great change in MHC class II and Ii gene expression in vivo.
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Using flow cytometric analyses, the presence of cell surface MHC
class I and II molecules was examined on splenic B cells isolated from
CIITA-/- and WT mice (Fig. 4). Approximately 50–60% of the splenic
cells were B cells, and the CIITA-/- mice
showed a small increase in this population. In the
CIITA-/- mice, virtually all
B220+ B cells were MHC class II negative
(99.5%). In the control mice, nearly all of
B220+ B cells were MHC class II positive
(92.3%). However, there was no significant difference in MHC class I
expression on B220+ B cells between the
CIITA-/- and control mice. The splenic
Mac-1+ cells were also normal in number but
devoid of MHC class II expression in the
CIITA-/- mice, whereas in the control mice,
60% of the Mac-1+ cells were MHC class II
positive (data not shown). Immunofluorescence studies were also
performed on tissue sections, and the results were identical with the
flow cytometric analyses (data not shown). Taken together, the RT-PCR,
Northern blot, flow cytometry, and fluorescent immunohistology data
clearly show that there is a great reduction of MHC class II expression
in the CIITA-/- mice.
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In I-Aß-/- (MHC class
II gene KO) mice, a sharp reduction in the number of
CD4+ T cells and a proportional increase in
CD8+ T cells were observed in the spleen, thymus,
and LNs (30). When splenic and thymic cells from
CIITA-/- mice were stained with anti-CD4
and anti-CD8 mAbs and analyzed by flow cytometry, we also saw a
great reduction of CD4+ T cells present only in
both the thymus and spleen (Fig. 5A). In the
CIITA-/- mice, CD4+ T
cells represent 1.8% of the cells in the thymus and 4.5% of the cells
in the spleen, whereas in the WT controls, CD4+ T
cells comprised 
14.3% in the thymus and 21.6% of the cells in the
spleen. There was a compensatory increase in CD8+
T cells (from 14.2% to 23.1%) in the spleens of the
CIITA-/- mice. There was also a slight increase
in CD4+ CD8+ T cells (from
79.4% to 92.5%) in the thymi of the
CIITA-/- mice.
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B shows thymus and spleen sections
from CIITA-/- and control mice. In thymic
sections from the CIITA-/- mice, very few cells
stained with anti-CD4; however, we saw a compensatory increase in
cells stained with anti-CD8 in the medulla compared with the normal
staining pattern seen in the WT mice (Fig. 5B, left). Spleen
sections from the CIITA-/- mice showed a lack
of perivascular staining with anti-CD4, with proportionally
increased staining with anti-CD8 (Fig. 5B, right); WT
mice showed a normal perivascular staining. The same results were
obtained with LNs (data not shown). Taken together, these data indicate that the differentiation of CD4+ T cells is greatly perturbed in the thymus in CIITA-/- mice due to the drastic reduction of MHC class II molecule expression. This leads to a decrease in the peripheral CD4+ T cell population and a compensatory up-regulation of CD8+ T cells in CIITA-/- mice.
Reduction of IgG but not IgM levels in CIITA-/- mice
Although the number of B220+ B cells in the
spleen appears to be normal in the CIITA-/-
mice, virtually all of these cells are MHC class II negative. When
serum IgM and IgG levels were examined, there was a slight increase in
serum IgM and a severe reduction in serum IgG levels in
CIITA-/- mice (Fig. 6). This parallels the finding in
I-Aß-/- mice and shows that
there is a defect in MHC class II-dependent Ig class-switching from IgM
to IgG (30, 31).
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-induced MHC class II
expression in CIITA-/- mice
CIITA is clearly an important molecule for both constitutive
expression and the IFN- induction of MHC class II expression. Using
the mice generated in this report, we confirmed the finding that the
IFN- induction of MHC class II was eliminated (data not shown)
(32). This was not surprising, because the role of CIITA
in the IFN- induction of MHC class II is well documented
(11, 12, 13). However, the role of CIITA in mediating the
induction of MHC class II expression by other biologic inducers had not
been elucidated previously. To address this, we tested the capacity of
IL-4 and LPS (endotoxin) to induce MHC class II expression in the
absence of CIITA. IL-4 and LPS are known to up-regulate MHC class II
expression on both B lymphocytes and macrophages (33),
whereas IFN- up-regulates expression on macrophages but not B cells.
As expected, i.v. injection of IL-4 increased MHC class II expression
on total splenic cells from WT mice (Fig. 7A). When these cells were
analyzed further, it was apparent that MHC class II was significantly
amplified on B220+ B cells and
Mac-1+ cells in the spleens of WT mice (Fig. 7A). In contrast, MHC class II expression was negligible in
cells isolated from CIITA-/- mice that had been
treated with IL-4. The CIITA-/- mean channel
fluorescence, although slightly above baseline, clearly shows an
absence of induction by IL-4 when compared with saline-treated controls
(Fig. 7A). Only 0.41% of all
CIITA-/- events fell outside of the MHC class
II negative quadrants, and a similar number of "positive" events
(0.43%) was seen with our isotype control (Fig. 7B).
Therefore, this low level of binding probably represents nonspecific
staining of our Abs and not actual MHC class II expression. Treatment
with LPS (Fig. 7C) produced similar results. Identical
results were obtained with the LNs of these animals (data not shown).
These data indicate that CIITA expression is pivotal for controlling
MHC class II induction by IL-4, endotoxin, and IFN-.
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Discussion |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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Three primary inducers were tested, and all three were shown to depend
upon CIITA for the induction of MHC class II expression. IFN- is the
most potent inducer of MHC class II, and many in vitro analyses have
pointed to CIITA as the critical molecule in mediating the IFN-
response; thus the involvement of CIITA in this response is not
surprising (11, 12, 13). Composite studies from our group and
other groups indicate that IFN- up-regulates CIITA promoter
activation, which then leads to the downstream activation of MHC class
II expression (34, 35). IFN- up-regulates the activity
of two distinct CIITA promoters: promoter III is most likely activated
directly by the IFN--induced phosphorylation of the STAT1 protein,
whereas promoter IV is activated primarily by interferon regulatory
factor-1 (IRF-1) and, to a lesser extent, by the STAT1 protein
(35). The IL-4 induction of MHC class II is less well
studied, and the role of CIITA in this response has not been tested.
Although IL-4 was known to induce the binding of DNA-binding proteins,
which recognize DNA sequences in the MHC class II promoter by gel shift
analysis, the involvement of these DNA-binding proteins in MHC class II
expression was not directly verified (36). The results in
this report indicate that IL-4 induction of MHC class II transcription
is in fact mediated by CIITA, and this dependency upon CIITA is present
in both B220+ B cells and
Mac-1+ cells. This finding provides a starting
point for revisiting the issue of MHC class II induction by IL-4.
Finally, endotoxin has long been shown to induce MHC class II, and
there is some evidence that endotoxin and IL-4 constitute overlapping
pathways (37). Others have shown that IL-1, a primary product of
endotoxin treatment, induces IL-4 (38). It is likely that
both IL-4 and endotoxin activate MHC class II expression by enhancing
the expression of CIITA.
These data clearly demonstrate that CIITA is a crucial regulator of MHC class II expression, with its elimination abrogating most of the MHC class II expression. However, RT-PCR analysis shows some residual MHC class II expression in all primary and secondary lymphoid tissues examined. Several attempts in our laboratory to identify the cell(s) harboring this CIITA-independent, MHC class II expression by immunohistochemistry and FACS have not generated credible data, because this cell is likely very rare. Previously, Chang et al. (26) detected MHC class II in the thymic tissue of their CIITA-/- mice (32). Since the preparation of this manuscript, Williams et al. have shown the presence of Ia expression among dendritic cells found in the LNs of CIITA knockouts, although the expression level was significantly reduced. Other reports have used mutants with defects in MHC class II expression to dissociate MHC class II expression from CIITA expression by in vitro analysis (39, 40, 41). All of these findings support a crucial role for CIITA-dependent MHC class II gene expression under a variety of conditions; however, one or more than one CIITA-independent pathway(s) also exist. The biologic function of both pathways will be of interest and testable with the mouse strain described here. Another consideration that is testable is the possibility that an isotype-specific control of MHC class II genes is differentially dependent upon CIITA (39, 42, 43).
The one difference between the CIITA-/- strain
reported here and the CIITA-/- mouse strain
produced by Chang et al. (32) is the level of Ii
expression. The CIITA-/- mice described here
exhibit a greater reduction of Ii gene expression, although this is
likely attributed to inherent differences in the assays used to measure
Ii RNA levels. The previous report used RT-PCR, whereas both PCR and
Northern blot analyses were used in this report. The RT-PCR assay is
more prone to artifacts, particularly in underestimating differences
among samples. In this report, the Northern blot analysis showed a
significant drop in the level of Ii gene expression, although the
reduction is less pronounced than that for MHC class II transcripts.
This is most likely due to the presence of additional regulatory
elements in the Ii promoter, such as Sp-1, NF-
B, and an additional
NF-Y binding site, all of which contribute to the up-regulation of Ii
(44, 45, 46). This dichotomy of MHC class II and Ii gene
expression has a biologic basis: in addition to its role in Ag
processing, Ii has also been shown to regulate/direct B cell
development (47).
Previously, we and others have demonstrated in cell lines that CIITA
can regulate the cytokine-induced (e.g., IFN-) expression of MHC
class I genes and Ags in vitro (48, 49). This regulation
is most evident in cell lines that either do not express or express
very low levels of basal MHC class I expression. In contrast, MHC class
I expression is not affected by CIITA in cell lines that express
moderate to high levels of MHC class I. The control of MHC class I
promoters by CIITA is mediated through the 
site in these promoters.
The site is similar but not identical with an AP-1 binding site,
and its interaction with AP-1 is, at best, poor. However, the
importance of the site is substantiated by genomic footprint
analysis, which shows that the in vivo occupancy of this site is
correlated with MHC class I gene expression (50).
The creation of CIITA-/- mice allowed us to determine whether CIITA can regulate MHC class I expression in vivo. This report shows that MHC class I expression is not grossly altered in these mice; however, it should be emphasized that the tissues examined in this report typically express relatively high levels of MHC class I. The effect of CIITA in vitro is only evident in cell lines with little MHC class I expression (49). Thus, the in vivo effect of CIITA on MHC class I expression may be cell type-restricted; further analyses will be necessary to resolve the physiologic significance of MHC class I induction by CIITA.
In summary, a CIITA gene KO mouse strain was created by the targeted
deletion of a region that includes the GTP-binding consensus sequence.
The CIITA-/- mice exhibited a near elimination
of constitutive MHC class II expression and induced expression in
response to IL-4, LPS, and IFN-. Effects on MHC class II expression
in this strain are correlated with a gross impairment of
CD4+ T cell maturation in the thymus and with the
depletion of these cells in the periphery. These mice will be useful as
a vehicle for gene knock-in experiments as well as for the study of the
biologic functions of CIITA and other molecules in the MHC class II
Ag-processing pathway.
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Footnotes |
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2 Y.I.-L. and J.F.P. contributed equally to this work.
3 Current address: Department of Medicine, Division of Nephrology, University of North Carolina, Chapel Hill, NC 27599-7155.
4 Address correspondence and reprint requests to Dr. Jenny Ting, CB7295, Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC, 27599-7295. E-mail address:
5 Abbreviations used in this paper: Ii, invariant chain; CIITA, class II transactivator; WT, wild type; LN, lymph node; KO, knockout; ES, embryonic stem.
Received for publication March 23, 1999. Accepted for publication June 2, 1999.
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References |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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ß dimers and facilitates peptide loading. Cell 82:155.[Medline]
mutants reveals that defects in CIITA or RFX result in defective class II MHC and Ii gene induction. Immunity 1:687.[Medline]
mediated by the transactivator gene CIITA. Science 265:106. requires cooperative interaction between Stat1 and USF-1. Immunity 8:157.[Medline]
, STAT1, and TGF-ß-regulated expression of the class II transactivator gene [In Process Citation]. J. Immunol. 160:233. gene. J. Immunol. 147:2377.[Abstract]
B/Rel binding sites in the major histocompatibility complex class II invariant chain promoter is dependent on cell-specific binding of different NF-B/Rel subunits. Mol. Cell. Biol. 14:2926. is crucial for two routes of IFN--induced MHC class I transactivation: the ISRE-mediated route and a novel pathway involving CIITA. Immunity 6:601.[Medline]
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R. K. Pai, M. Convery, T. A. Hamilton, W. H. Boom, and C. V. Harding Inhibition of IFN-{gamma}-Induced Class II Transactivator Expression by a 19-kDa Lipoprotein from Mycobacterium tuberculosis: A Potential Mechanism for Immune Evasion J. Immunol., July 1, 2003; 171(1): 175 - 184. [Abstract] [Full Text] [PDF]
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J.-M. Waldburger, S. Rossi, G. A. Hollander, H.-R. Rodewald, W. Reith, and H. Acha-Orbea Promoter IV of the class II transactivator gene is essential for positive selection of CD4+ T cells Blood, May 1, 2003; 101(9): 3550 - 3559. [Abstract] [Full Text] [PDF]
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L. A. Otten, F. Tacchini-Cottier, M. Lohoff, F. Annunziato, L. Cosmi, L. Scarpellino, J. Louis, V. Steimle, W. Reith, and H. Acha-Orbea Deregulated MHC Class II Transactivator Expression Leads to a Strong Th2 Bias in CD4+ T Lymphocytes J. Immunol., February 1, 2003; 170(3): 1150 - 1157. [Abstract] [Full Text] [PDF]
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 E. V. Acosta Rodriguez, E. Zuniga, C. L. Montes, and A. Gruppi Interleukin-4 biases differentiation of B cells from Trypanosoma cruzi-infected mice and restrains their fratricide: role of Fas ligand down-regulation and MHC class II-transactivator up-regulation J. Leukoc. Biol., January 1, 2003; 73(1): 127 - 136. [Abstract] [Full Text] [PDF]
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O. Stuve, S. Youssef, A. J. Slavin, C. L. King, J. C. Patarroyo, D. L. Hirschberg, W. J. Brickey, J. M. Soos, J. F. Piskurich, H. A. Chapman, et al. The Role of the MHC Class II Transactivator in Class II Expression and Antigen Presentation by Astrocytes and in Susceptibility to Central Nervous System Autoimmune Disease J. Immunol., December 15, 2002; 169(12): 6720 - 6732. [Abstract] [Full Text] [PDF]
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R. K. Pai, D. Askew, W. H. Boom, and C. V. Harding Regulation of Class II MHC Expression in APCs: Roles of Types I, III, and IV Class II Transactivator J. Immunol., August 1, 2002; 169(3): 1326 - 1333. [Abstract] [Full Text] [PDF]
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S. M. Tompkins, J. Padilla, M. C. Dal Canto, J. P.-Y. Ting, L. Van Kaer, and S. D. Miller De Novo Central Nervous System Processing of Myelin Antigen Is Required for the Initiation of Experimental Autoimmune Encephalomyelitis J. Immunol., April 15, 2002; 168(8): 4173 - 4183. [Abstract] [Full Text] [PDF]
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 J.-M. Waldburger, T. Suter, A. Fontana, H. Acha-Orbea, and W. Reith Selective Abrogation of Major Histocompatibility Complex Class II Expression on Extrahematopoietic Cells in Mice Lacking Promoter IV of the Class II Transactivator Gene J. Exp. Med., August 13, 2001; 194(4): 393 - 406. [Abstract] [Full Text] [PDF]
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