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Cheong-Hee Chang

Publications and source records attributed to Cheong-Hee Chang.

At least 19 recordsLinked to original sources
PubMed2006

Protein kinase C delta is essential to maintain CIITA gene expression in B cells.

Expression of MHC class II genes requires CIITA. Although the transactivation function of CIITA is well characterized, the signaling events that regulate CIITA expression are less understood. In this study, we report that CIITA expression in B cells depends on protein kinase Cdelta (PKCdelta). PKCdelta controls CIITA gene transcription mainly via modulating CREB recruitment to the CIITA promoter without affecting CIITA mRNA stability. Inhibition of PKCdelta by a pharmacological inhibitor or knocking down of endogenous PKCdelta expression by small interfering RNA reduced CREB binding to the CIITA promoter. The decrease of CIITA gene expression in the presence of the PKCdelta inhibitor was prevented by ectopically expressing a constitutively active form of CREB. In addition, histone acetylation of the CIITA promoter is regulated by PKCdelta since the PKCdelta inhibitor treatment or PKCdelta small interfering RNA resulted in decreased histone acetylation. Taken together, our study reveals that PKCdelta is an important signaling molecule necessary to maintain CIITA and MHC class II expression in B cells.

B-Lymphocytes↗
PubMed2006

ERK and p38 MAPK signaling pathways negatively regulate CIITA gene expression in dendritic cells and macrophages.

The CIITA is a master regulator for MHC class II expression, but the signaling events that control CIITA expression remain poorly understood. In this study, we report that both constitutive and IFN-gamma-inducible expression of CIITA in mouse bone marrow-derived dendritic cells (DC) and macrophages, respectively, are regulated by MAPK signals. In DC, the inhibitory effect of LPS on CIITA expression was prevented by MyD88 deficiency or pharmacological MAPK inhibitors specific for MEK (U0126) and p38 (SB203580), but not JNK (SP600125). In macrophages, LPS inhibited IFN-gamma-inducible CIITA and MHC class II expression without affecting expression of IFN regulatory factor-1 and MHC class I. Blocking ERK and p38 by MAPK inhibitors not only rescued LPS-mediated inhibition, but also augmented IFN-gamma induction of CIITA. Moreover, the induction of CIITA by IFN-gamma was enhanced by overexpressing MAPK phosphatase-1 that inactivates MAPK. Conversely, CIITA expression was attenuated in the absence of MAPK phosphatase-1. The down-regulation of CIITA gene expression by ERK and p38 was at least partly due to decreased histone acetylation of the CIITA promoter. Our study indicates that both MAPK and phosphatase play an important role for CIITA regulation in DC and macrophages.

Adaptor Proteins, Signal Transducing↗
PubMed2006

Negative regulation of MHC class II gene expression by CXCR4.

OBJECTIVE: CXCR4 is overexpressed in 23 types of cancers of both hematopoietic and nonhematopoietic origin. Based on the known role of CXCR4 and its ligand CXCL12 in homing of hematopoietic cells, CXCR4 is likely to play a role in metastasis. We have initiated a study aimed at dissecting additional functions of CXCR4 in cancer cells, particularly in relation to the immune system. MATERIALS AND METHODS: RNA from CXCR4+ and CXCR4- subpopulations of MDA-MB-231 breast cancer cells was subjected to microarray analysis. Cell surface expression of CXCR4 and MHC class II proteins were determined by flow cytometry. Real-time PCR was used for measuring mRNA levels of MHC class II and CIITA, the master regulator of MHC class II gene expression. RESULTS: 1988 genes were differentially expressed (p < 0.001) between CXCR4+ and CXCR4- cells. The expression of class II genes HLA-DPalpha1, HLA-DQbeta1, HLA-DRalpha, HLA-DRbeta1, HLA-DRbeta3, and CD74 was lower by 2.6-fold to eightfold in CXCR4+ cells compared to CXCR4- cells. Basal and IFN-gamma-inducible HLA-DR mRNA and protein levels were lower in CXCR4+ cells than in CXCR4- cells. HLA-DR mRNA expression in both cell types was reduced by CXCL12; the ability of CXCL12 to reduce HLA-DR was lower in cells expressing short interfering RNA against CXCR4. PKA inhibitor H89 and the SRC kinase inhibitor PP2 increased HLA-DR expression in CXCR4+ cells. The basal but not IFN-gamma-inducible expression of CIITA was 2.5-fold higher in CXCR4- cells compared to CXCR4+ cells. CD34+/CD38- hematopoietic cells from the human bone marrow contain a distinct CXCR4+/HLA-DR- subpopulation of cells. CONCLUSION: CXCR4 may influence the immune system under physiologic and pathologic conditions through negative regulation of MHC class II expression, possibly through PKA and SRC kinase.

Cell Line↗
PubMed2006

Class II transactivator-mediated regulation of major histocompatibility complex class II antigen expression is important for hematopoietic progenitor cell suppression by chemokines and iron-binding proteins.

OBJECTIVE: Iron-binding proteins H-ferritin (HF) and lactoferrin (LF), as well as chemokines, tumor necrosis factor (TNF)-alpha, and interferon (IFN)-gamma suppress hematopoietic progenitor cell (HPC) proliferation. Major histocompatibility complex (MHC) class II antigens have been associated with suppressive effects of HF and LF. Because the transcription factor class II transactivator (CIITA) regulates expression of MHC class II antigens, we evaluated influences of CIITA and MHC class II antigens on suppression of colony formation by murine bone marrow HPC in response to HF, LF, CC, and CXC chemokines, TNF-alpha, and IFN-gamma. We also evaluated hematopoiesis in mice deficient in both CIITA and MHC class II antigens (CIITA -/-), in mice deficient in MHC class II antigens but not in CIITA (MHC class II -/-), and in mice deficient in CIITA but not in MHC class II antigens (CIITA-IE). MATERIALS AND METHODS: HF, LF, CCL3/MIP-1alpha, CXCL5/ENA-78, CXCL8/IL-8, CCL5/RANTES, TNF-alpha, and IFN-gamma were assessed for effects on colony formation by bone marrow HPC (colony-forming unit granulocyte-macrophage, burst-forming unit erythroid, and colony-forming unit multipotential) stimulated in vitro by combinations of growth factors including erythropoietin, stem cell factor, pokeweed mitogen mouse spleen cell conditioned medium, and hemin. Bone marrow cells were from CIITA -/-, MHC class II antigen -/-, CIITA-IE, and littermate control mice. We also evaluated cycling status (percent cells in S-phase) and absolute numbers of marrow and spleen HPC in these mice. RESULTS: Multiple growth factor-stimulated colony formation by control bone marrow HPC was significantly suppressed by HF, LF, CCL3, CXCL5, CXCL8, TNF-alpha, and IFN-gamma, but not by CCL5. However, HPC from CIITA -/- and MHC class II antigen -/- mouse marrow was insensitive to inhibition by HF, LF, CCL3, CXCL5, CXCL8, and CCL5; these HPC were inhibited by TNF-alpha and IFN-gamma. Restoration of MHC class II expression in CIITA -/- (CIITA-IE) mice restored responsiveness of HPC to inhibition by HF, LF, CCL3, CXCL5, and CXCL8. Increased cycling of splenic HPC in CIITA -/- and MHC class II antigen -/-, compared to control and CIITA-IE, mice was noted. CONCLUSIONS: Myelosuppressive effects of iron-binding proteins HF and LF and chemokines CCL3, CXCL5, and CXCL8 on mouse bone marrow HPC require expression of MHC class II antigens, and CIITA is involved in this responsiveness through its regulation of expression of MHC class II antigens.

Animals↗
PubMed2006

Pulmonary immunity to viral infection: adenovirus infection of lung dendritic cells renders T cells nonresponsive to interleukin-2.

Adenovirus (Ad) infection has been identified as predisposing hosts to the development of pulmonary disease through unknown mechanisms. Lung dendritic cells (DCs) are vital for initiating pulmonary immune responses; however, the effects of Ad infection on primary lung DC have not been studied. In contrast to the effects on bone marrow- and monocyte-derived DCs, the current study shows that Ad infection of murine BALB/c lung DCs in vitro and in vivo suppresses DC-induced T-cell proliferation. The effect of Ad on DCs was not due to a downregulation of major histocompatibility complex or costimulatory molecules. Analysis of the production of interleukin-12 (IL-12), alpha interferon (IFN-alpha), and IFN-gamma by the Ad-infected DCs shows no significant differences over noninfected control lung DCs. Ad-induced suppression was not due to a deficiency of IL-2 or other DC-secreted factors and was dependent on viral protein synthesis, as UV irradiation of Ad abrogated the suppressive effect. Results suggest that Ad-infected DCs induce T cells to be nonresponsive to IL-2 during primary coculture, as the addition of IL-2 in secondary cultures recovered T-cell proliferation. In vivo studies supported in vitro results showing that Ad infection resulted in lung T cells with decreased proliferative ability. This study demonstrates that Ad infection induces local immunoincompetence by altering DC-T-cell interactions.

Adenoviridae Infections↗
PubMed2005

MAP kinase phosphatase 1 controls innate immune responses and suppresses endotoxic shock.

Septic shock is a leading cause of morbidity and mortality. However, genetic factors predisposing to septic shock are not fully understood. Excessive production of proinflammatory cytokines, particularly tumor necrosis factor (TNF)-alpha, and the resultant severe hypotension play a central role in the pathophysiological process. Mitogen-activated protein (MAP) kinase cascades are crucial in the biosynthesis of proinflammatory cytokines. MAP kinase phosphatase (MKP)-1 is an archetypal member of the dual specificity protein phosphatase family that dephosphorylates MAP kinase. Thus, we hypothesize that knockout of the Mkp-1 gene results in prolonged MAP kinase activation, augmented cytokine production, and increased susceptibility to endotoxic shock. Here, we show that knockout of Mkp-1 substantially sensitizes mice to endotoxic shock induced by lipopolysaccharide (LPS) challenge. We demonstrate that upon LPS challenge, Mkp-1-/- cells exhibit prolonged p38 and c-Jun NH2-terminal kinase activation as well as enhanced TNF-alpha and interleukin (IL)-6 production compared with wild-type cells. After LPS challenge, Mkp-1 knockout mice produce dramatically more TNF-alpha, IL-6, and IL-10 than do wild-type mice. Consequently, Mkp-1 knockout mice develop severe hypotension and multiple organ failure, and exhibit a remarkable increase in mortality. Our studies demonstrate that MKP-1 is a pivotal feedback control regulator of the innate immune responses and plays a critical role in suppressing endotoxin shock.

Animals↗
PubMed2005

Disruption of MHC class II-restricted antigen presentation by vaccinia virus.

Vaccinia virus (VV), currently used in humans as a live vaccine for smallpox, can interfere with host immunity via several discrete mechanisms. In this study, the effect of VV on MHC class II-mediated Ag presentation was investigated. Following VV infection, the ability of professional and nonprofessional APC to present Ag and peptides to CD4+ T cells was impaired. Viral inhibition of class II Ag presentation could be detected within 1 h, with diminished T cell responses dependent upon the duration of APC infection and virus titer. Exposure of APC to replication-deficient virus also diminished class II Ag presentation. Virus infection of APC perturbed Ag presentation by newly synthesized and recycling class II molecules, with disruptions in both exogenous and cytoplasmic Ag presentation. Virus-driven expression of an endogenous Ag, failed to restore T cell responsiveness specific for this Ag in the context of MHC class II molecules. Yet, both class II protein steady-state and cell surface expression were not altered by VV. Biochemical and functional analysis revealed that VV infection directly interfered with ligand binding to class II molecules. Together, these observations suggest that disruption of MHC class II-mediated Ag presentation may be one of multiple strategies VV has evolved to escape host immune surveillance.

Animals↗
PubMed2005

MHC class II expression through a hitherto unknown pathway supports T helper cell-dependent immune responses: implications for MHC class II deficiency.

MHC class II (MHCII) deficiency or bare lymphocyte syndrome (BLS) is a severe immunodeficiency characterized by deficient T helper (Th)-cell-dependent immunity. The disease is caused by defects of the MHCII promoter complex resulting in low or absent MHCII expression. We demonstrate in a murine model of MHCII deficiency (RFX5- or CIITA-deficient mice) that residual MHCII expression by professional antigen-presenting cells (APCs) is sufficient to support activation of adoptively transferred Th cells. Furthermore, upon transplantation of WT thymic epithelium, we observed development of endogenous Th cells with restoration of Th-cell-dependent antibody responses and immunity to cytomegalovirus infection, thus opening the possibility of an alternative treatment regimen for BLS. Residual MHCII expression was further induced by the presence of Th cells and also other stimuli. Analysis of CIITA/RFX5 double-deficient animals revealed that this inducible MHCII expression is genetically independent of the known promoter complex and thus constitutes an alternative MHCII expression pathway. In these experiments, we also detected a novel repressive function of the RFX complex in the absence of CIITA.

Animals↗
PubMed2005

Interleukin (IL)-4 inhibits IL-10 to promote IL-12 production by dendritic cells.

Interleukin (IL)-4 is known to be the most potent cytokine that can initiate Th2 cell differentiation. Paradoxically, IL-4 instructs dendritic cells (DCs) to promote Th1 cell differentiation. We investigated the mechanisms by which IL-4 directs CD4 T cells toward the Th1 cell lineage. Our study demonstrates that the IL-4-mediated induction of Th1 cell differentiation requires IL-10 production by DCs. IL-4 treatment of DCs in the presence of lipopolysaccharide or CpG resulted in decreased production of IL-10, which was accompanied by enhanced IL-12 production. In IL-10-deficient DCs, the level of IL-12 was greatly elevated and, more importantly, the ability of IL-4 to up-regulate IL-12 was abrogated. Interestingly, IL-4 inhibited IL-10 production by DCs but not by B cells. The down-regulation of IL-10 gene expression by IL-4 depended on Stat6 and was at least partly caused by decreased histone acetylation of the IL-10 promoter. These data indicate that IL-4 plays a key role in inducing Th1 cell differentiation by instructing DCs to produce less IL-10.

Acetylation↗
PubMed2005

A role for caspases in controlling IL-4 expression in T cells.

Although caspase activation is critical for T cell proliferation following activation, the role of caspases in T cell differentiation is unclear. In this study, we have examined the effect of inhibition of caspases on the process of Th1/Th2 differentiation. Naive CD4+ T cells activated under neutral differentiation conditions in the presence of the pan caspase inhibitor benzyloxycarbonyl-Val-Ala-Asp (Z-VAD) fluoromethylketone showed increased Th2 cell differentiation concomitant with an up-regulation of GATA-3. Z-VAD induced optimal Th2 differentiation when T cells were stimulated under strong primary activation conditions. Treatment of naive CD4+ T cells with Z-VAD under strong activation conditions led to a 6-fold increase in IL-4 mRNA compared with control-treated T cells. The Z-VAD-induced increase in IL-4 transcription occurred within 24 h of activation and was independent of Stat6. IFN-gamma mRNA expression was not affected by Z-VAD at the 24-h time point. Z-VAD did not augment IL-4 expression from a committed Th2 cell, suggesting that caspases regulate IL-4 expression specifically during primary T cell activation. Z-VAD did not augment IL-12-driven Th1 differentiation. Activation of T cells in the presence of Z-VAD led to a specific increase in the expression of the transcription factor c-fos. Lastly, retrovirus-mediated expression of the antiapoptotic protein Bcl-2 resulted in an enhancement of Th2 cytokine expression, suggesting that inhibition of caspase activation by Bcl-2 can also modulate IL-4 expression. These findings reveal a novel regulatory mechanism of cytokine expression by caspases, and may explain how signaling pathways that inhibit apoptosis tend to promote Th2 differentiation.

Amino Acid Chloromethyl Ketones↗
PubMed2005

Enhanced production of IL-10 by dendritic cells deficient in CIITA.

Dendritic cells (DC) are professional APCs that play a critical role in regulating immunity. In DC, maturation-induced changes in MHC class II expression and Ag presentation require transcriptional regulation by CIITA. To study the role of CIITA in DC, we evaluated key cell functions in DC from CIITA-deficient (CIITA(-/-)) mice. The ability to take up Ag, measured by fluid phase endocytosis, was comparable between CIITA(-/-) and control DC. Although CIITA(-/-) DC lack MHC class II, they maintained normal expression of costimulatory molecules CD80, CD86, and CD40. In contrast, CIITA(-/-) DC activated with LPS or CpG expressed increased IL-10 levels, but normal levels of TNF-alpha and IL-12 relative to control. Enhanced IL-10 was due to greater IL-10 mRNA in CIITA(-/-) DC. Abeta(-/-) DC, which lack MHC class II but express CIITA normally, had exhibited no difference in IL-10 compared with control. When CIITA was cotransfected with an IL-10 promoter-reporter into a mouse monocyte cell line, RAW 264.7, IL-10 promoter activity was decreased. In addition, reintroducing CIITA into CIITA(-/-) DC reduced production of IL-10. In all, these data suggest that CIITA negatively regulates expression of IL-10, and that CIITA may direct DC function in ways that extend beyond control of MHC class II.

Animals↗
PubMed2005

Graft rejection mediated by CD4+ T cells via indirect recognition of alloantigen is associated with a dominant Th2 response.

CD4(+) T cells that respond to indirectly presented alloantigen have been shown to mediate chronic rejection, however, the role of the indirect pathway in acute rejection has yet to be completely elucidated. To this end, BALB/c or C57BL/6 mice were depleted of CD8(+) T cells and transplanted with class II transactivator (CIITA)-deficient cardiac allografts, which cannot directly present class II alloantigens to CD4(+) T cells. In this manner, the rejection response by CD4(+) cells was forced to rely upon the indirect recognition pathway. When not depleted of CD8(+) cells, both BALB/c and C57BL/6 mice rejected CIITA-/- allografts and a polarized Th1 response was observed. In contrast, when BALB/c recipients of CIITA-/- allografts were depleted of CD8(+) T cells, the grafts were acutely rejected and a strong Th2 response characterized by eosinophil influx into the graft was observed. Interestingly, CD8-depleted C57BL/6 recipients of CIITA-/- allografts did not acutely reject their transplants and a Th2 response was not mounted. These findings indicate that CD4(+) T cells responding to indirectly presented alloantigens mediate graft rejection in a Th2-dominant manner, and provide further evidence for the role of Th2 responses in acute graft rejection.

Animals↗
PubMed2005

Constitutive expression of CIITA directs CD4 T cells to produce Th2 cytokines in the thymus.

We generated mice expressing a human type III CIITA transgene (CIITA Tg) under control of the CD4 promoter to study the role of CIITA in CD4 T cell biology. The transgene is expressed in peripheral CD4 and CD8 T cells, as well as in thymocytes. When CD4 T cells were differentiated towards the Th2 lineage, both control and CIITA Tg Th2 cells expressed similar levels of Th2 cytokines. Th1 cells from control and CIITA Tg mice cells produced comparable levels of IFN-gamma. CIITA Tg Th1 cells also expressed IL-4, IL-5, and IL-13 in the absence of Stat6. There was an approximate 10-fold increase in the number of peripheral naïve CD4 T cells and NK1.1- thymocytes producing IL-4 from CIITA Tg mice compared to control mice. Finally, Th1 cells from irradiated control mice reconstituted with CIITA Tg bone marrow displayed the same cytokine production profiles as Th1 cells from CIITA Tg mice. Together, our data demonstrate that CIITA expression pre-disposes CD4 T cells to produce Th2 type cytokines. Moreover, phenotypic similarities between Th1 cells expressing the CIITA transgene and CIITA deficient Th1 cells suggest that the role of CIITA in cytokine regulation is complex and may reflect both direct and indirect mechanisms of T cell development and differentiation.

Adoptive Transfer↗
PubMed2005

An alternate pathway for CD4 T cell development: thymocyte-expressed MHC class II selects a distinct T cell population.

Conventional understanding of CD4 T cell development is that the MHC class II molecules on cortical thymic epithelial cell are necessary for positive selection, as demonstrated in mouse models. Clinical data, however, show that hematopoietic stem cells reconstitute CD4 T cells in patients devoid of MHC class II. Additionally, CD4 T cells generated from human stem cells in immunocompromised mice were restricted to human, but not mouse, MHC class II. These studies suggest an alternative pathway for CD4 T cell development that does not normally exist in mice. MHC class II is expressed on developing human thymocytes, indicating a possible role of MHC II on thymocytes for CD4 T cell generation. Therefore, we created mice in which MHC class II is expressed only on T lineage cells. Remarkably, the CD4 compartment in such mice is efficiently reconstituted with unique specificity, demonstrating a novel thymocyte-driven pathway of CD4 T cell selection.

Animals↗
PubMed2004

Altered Th1 cell differentiation programming by CIITA deficiency.

CD4 T cell differentiation is a complex process affected by many transcription factors interacting in a tightly regulated manner. We have previously shown that CIITA-deficient mouse Th1 cells expressed Th2-type cytokines, while IFN-gamma expression was normal. In this study, we show that CIITA-deficient Th1 cells contain three distinct populations: cells secreting IL-4 alone, IFN-gamma alone, and both IL-4 and IFN-gamma together. This novel phenotype is stable over multiple rounds of stimulation in the presence of Th1-inducing factors. CIITA-deficient Th1 cells require TCR-mediated signaling to express Th2 cytokines, and this occurs with similar kinetics as wild-type Th2 cells. Both GATA-3 and IL-4 appear to be required for CIITA-deficient Th1 cells to express Th2-type cytokines. Interestingly, however, CIITA-deficient Th1 cells can produce IL-4 in the absence of exogenous IL-4. Introducing either CIITA or antisense GATA-3 during Th1 differentiation partially reduces Th2-type cytokine expression. With the exception of Th2-type cytokine expression, Th1 differentiation occurs normally in the absence of CIITA, as measured by expression of T-bet, IL-12Rbeta2, IL-18Ralpha, and IFN-gamma. Therefore, CIITA plays a key role to repress Th2-type cytokine expression as naive CD4 T cells differentiate toward the Th1 lineage.

Animals↗
PubMed2004

Cathepsin E: a novel target for regulation by class II transactivator.

The aspartic proteinase cathepsin E (CatE) has been implicated in Ag processing. In this study we report that CatE expression is negatively regulated by the MHC class II transactivator (CIITA). CIITA-deficient murine and human B cells expressed greater CatE than wild-type B cells, whereas overexpression of CIITA in a human gastric carcinoma cell line, AGS, resulted in decreased CatE mRNA and protein. AGS cells expressing CIITA also exhibited decreased processing of OVA Ag. Inhibition of CatE expression is specific to the type III CIITA isoform and maps to the acidic and proline/serine/threonine-rich (PST) protein domains of CIITA. We found that CatE expression is inducible by PU.1 and p300, and that this induction can be reversed by CIITA. These findings demonstrate a novel phenomenon: regulation of CatE Ag processing by CIITA in an isoform-dependent manner.

Animals↗
PubMed2004

Mechanisms governing B cell developmental defects in invariant chain-deficient mice.

Invariant chain (Ii)-deficient mice exhibit profound B cell defects that have remained poorly understood, because they could not be simply explained by impaired Ag presentation. We found that Ii deficiency induced cell autonomous defects of two distinct B cell lineages. The life span of mature follicular (FO) B cells was reduced, accounting for their markedly decreased frequency, whereas, in contrast, marginal zone (MZ) B cells accumulated. Other Ii-expressing lineages such as B1 B cells and dendritic cells were unaffected. Surprisingly, the life span of FO B cells was fully corrected in Ii/I-Abeta doubly deficient mice, revealing that Ii-free I-Abeta chains alter FO B cell survival. In contrast, the accumulation of MZ B cells was controlled by a separate mechanism independent of I-Abeta. Interestingly, in Ii-deficient mice lacking FO B cells, the MZ B cells invaded the FO zone, suggesting that intact follicules contribute to the retention of B cells in the MZ. These findings reveal unexpected consequences of Ii deficiency on the development and organization of B cell follicles.

Animals↗