Class Ib MHC–Mediated Immune Interactions Play a Critical Role in Maintaining Mucosal Homeostasis in the Mammalian Large Intestine

Abstract The failure to achieve durable engraftment following prenatal transplantation in immunologically normal human fetal recipients calls for a closer examination of the fetal immune response to allotransplantation. Previous studies in mice suggest that the fetal innate immune system functions as a critical barrier to allogeneic engraftment mediated by recognition of MHC class Ib antigens. We hypothesized that Qa-2 (the putative murine homolog for HLA-G) might play an essential role in the modulation of fetal immune response to prenatally transplanted allogeneic cells. To address this hypothesis, we utilized B6.K1 mice as a donor strain. B6.K1 mice are Qa-2 deficient and are congenic with wild-type B6.Ly5.2 mice. Light density mononuclear cells (LDMCs) were harvested from the livers of 14 dpc fetal B6.K1 or B6.Ly5.2 mice and transplanted into age-matched allogeneic Balb/c fetal recipients at a dose of 105 cells per fetus. Following delivery, peripheral blood chimerism was assessed serially in the recipients. Survival to weaning was similar between the groups without evidence of GVHD. At 3 weeks of age, recipients of B6.K1 cells demonstrated significantly lower peripheral blood chimerism levels than recipients of B6.Ly5.2 control cells. By 6 months of age, nearly all of the recipients of B6.K1 cells had lost their chimerism. Conversely, the chimerism levels in recipients of B6.Ly5.2 control cells remained stable suggesting that donor Qa-2 expression was essential for allograft survival. To assess the competitive capacity of the B6.K1 donor cells in the absence of immunologic disparity, B6.K1 or B6.Ly5.2 fetal liver LDMCs were transplanted into congenic B6.Ly5.1 hosts at the same cell dose per fetus. This resulted in stable long-term engraftment of the B6.K1 cells in all recipients. Chimerism levels were identical to those recipients who received B6.Ly5.2 control cells, confirming that the engraftment disparities observed in the allogeneic recipients resulted from immunologic rejection. To assess the resilience of this apparent Qa-2-dependent innate immune barrier, the allogeneic transplantation experiments were then repeated at a ten-fold higher donor cell dose (106 cells/fetus). Early chimerism levels remained significantly lower in allogeneic recipients of Qa-2 deficient cells compared to controls. However, recipients of B6.K1 cells maintained their engraftment for more than 6 months indicating that the Qa-2-dependent fetal immune barrier may be overcome with higher levels of circulating antigen. From these experiments we conclude: Host allorecognition of the class Ib antigen Qa-2 is crucial for durable engraftment following in utero transplantation; The failed engraftment of Qa-2 deficient hematopoietic cells does not result from a defective competitive engraftment capacity; Qa-2 dependent fetal immune rejection may be diminished by higher levels of early chimerism. These experiments provide direct evidence for the critical role of MHC class Ib antigens in regulation of the fetal immune response to allotransplantation. Additionally, the demonstration of reliable engraftment following transplantation of higher cell doses provides a translationally relevant approach to enhance the clinical success of prenatal transplantation in immunologically normal hosts.

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Role of PD-L1 in Gut Mucosa Tolerance and Chronic Inflammation

International Journal of Molecular Sciences ◽

10.3390/ijms21239165 ◽

2020 ◽

Vol 21 (23) ◽

pp. 9165

Author(s):

Marina Chulkina ◽

Ellen J. Beswick ◽

Irina V. Pinchuk

Keyword(s):

Current Knowledge ◽

Critical Role ◽

The Body ◽

Regulatory Cells ◽

Gi Tract ◽

Therapeutic Approaches ◽

Gut Mucosa ◽

Mucosal Homeostasis ◽

Gi Mucosa

The gastrointestinal (GI) mucosa is among the most complex systems in the body. It has a diverse commensal microbiome challenged continuously by food and microbial components while delivering essential nutrients and defending against pathogens. For these reasons, regulatory cells and receptors are likely to play a central role in maintaining the gut mucosal homeostasis. Recent lessons from cancer immunotherapy point out the critical role of the B7 negative co-stimulator PD-L1 in mucosal homeostasis. In this review, we summarize the current knowledge supporting the critical role of PD-L1 in gastrointestinal mucosal tolerance and how abnormalities in its expression and signaling contribute to gut inflammation and cancers. Abnormal expression of PD-L1 and/or the PD-1/PD-L1 signaling pathways have been observed in the pathology of the GI tract. We also discuss the current gap in our knowledge with regards to PD-L1 signaling in the GI tract under homeostasis and pathology. Finally, we summarize the current understanding of how this pathway is currently targeted to develop novel therapeutic approaches.

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ApoB mRNA editing is mediated by a coordinated modulation of multiple apoB mRNA editing enzyme components

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.00118.2006 ◽

2007 ◽

Vol 292 (1) ◽

pp. G53-G65 ◽

Cited By ~ 14

Author(s):

Zhigang Chen ◽

Thomas L. Eggerman ◽

Amy P. Patterson

Keyword(s):

Large Intestine ◽

Rna Binding ◽

Binding Protein ◽

Critical Role ◽

Regulatory Protein ◽

Intestinal Cell ◽

Mrna Editing ◽

Apo B ◽

Apob Mrna ◽

Editing Enzyme

Apolipoprotein (apo)B mRNA editing is accomplished by a large multiprotein complex. How these proteins interact to achieve the precise single-nucleotide change induced by this complex remains unclear. We investigated the relationship between altered apoB mRNA editing and changes in editing enzyme components to evaluate their roles in editing regulation. In the mouse fetal small intestine, we found that the dramatic developmental upregulation of apoB mRNA editing from ∼3% to 88% begins with decreased levels of inhibitory CUG binding protein 2 (CUGBP2) expression followed by increased levels of apoB mRNA editing enzyme (apobec)-1 and apobec-1 complementation factor (ACF) (4- and 8-fold) and then by decreased levels of the inhibitory components glycine-arginine-tyrosine-rich RNA binding protein (GRY-RBP) and heterogeneous nuclear ribonucleoprotein (hnRNP)-C1 (75% and 56%). In contrast, the expression of KH-type splicing regulatory protein (KSRP), apobec-1 binding protein (ABBP)1, ABBP2, and Bcl-2-associated athanogene 4 (BAG4) were unaltered. In the human intestinal cell line Caco-2, the increase of apoB mRNA editing from ∼1.7% to ∼23% was associated with 6- and 3.2-fold increases of apobec-1 and CUGBP2, respectively. In the mouse large intestine, the editing was 48% and had a 2.7-fold relatively greater CUGBP2 level. Caco-2 and the large intestine thus have increased instead of decreased CUGBP2 and a lower level of editing, suggesting that inhibitory CUGBP2 may play a critical role in the magnitude of editing regulation. Short interfering RNA-mediated gene-specific knockdown of CUGBP2, GRY-RBP, and hnRNP-C1 resulted in increased editing in Caco-2 cells, consistent with their known inhibitory function. These data suggest that a coordinated expression of editing components determines the magnitude and specificity of apoB mRNA editing.

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Induction of M3-Restricted Cytotoxic T Lymphocyte Responses by N-Formylated Peptides Derived from Mycobacterium tuberculosis

Journal of Experimental Medicine ◽

10.1084/jem.193.10.1213 ◽

2001 ◽

Vol 193 (10) ◽

pp. 1213-1220 ◽

Cited By ~ 48

Author(s):

Taehoon Chun ◽

Natalya V. Serbina ◽

Dawn Nolt ◽

Bin Wang ◽

Nancy M. Chiu ◽

...

Keyword(s):

T Cells ◽

Mycobacterium Tuberculosis ◽

Cd8 T Cells ◽

Cytotoxic T Lymphocyte ◽

Critical Role ◽

Spleen And Lymph Nodes ◽

Mhc Class Ia ◽

Lymphocyte Responses ◽

Peptide Binding Assay ◽

Class Ib

Major histocompatibility complex (MHC) class I–restricted CD8+ T cells play a critical role in the protective immunity against Mycobacterium tuberculosis (Mtb). However, only a few Mtb peptides recognized by MHC class Ia–restricted CD8+ T cells have been identified. Information on epitopes recognized by class Ib–restricted T cells is even more limited. M3 is an MHC class Ib molecule that preferentially presents N-formylated peptides to CD8+ T cells. Because bacteria initiate protein synthesis with N-formyl methionine, the unique binding specificity of M3 makes it especially suitable for presenting these particular bacterial epitopes. We have scanned the full sequence of the Mtb genome for NH2-terminal peptides that share features with other M3-binding peptides. Synthetic peptides corresponding to these sequences were tested for their ability to bind to M3 in an immunofluorescence-based peptide-binding assay. Four of the N-formylated Mtb peptides were able to elicit cytotoxic T lymphocytes (CTLs) from mice immunized with peptide-coated splenocytes. The Mtb peptide–specific, M3-restricted CTLs lysed the Mtb-infected macrophages effectively, suggesting that these N-formylated Mtb peptides are presented as the naturally processed epitopes by Mtb-infected cells. Furthermore, T cells from Mtb-infected lungs, spleen, and lymph nodes responded to N-formylated Mtb peptides in an M3-restricted manner. Taken together, our data suggest that M3-restricted T cells may participate in the immune response to Mtb.

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Krüppel-like factor KLF10 deficiency predisposes to colitis through colonic macrophage dysregulation

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.00309.2015 ◽

2015 ◽

Vol 309 (11) ◽

pp. G900-G909 ◽

Cited By ~ 11

Author(s):

Konstantinos A. Papadakis ◽

James Krempski ◽

Phyllis Svingen ◽

Yuning Xiong ◽

Olga F. Sarmento ◽

...

Keyword(s):

Critical Role ◽

Experimental Colitis ◽

Macrophage Phenotype ◽

Inflammatory Conditions ◽

Tnf Α ◽

Mucosal Homeostasis ◽

Anti Inflammatory ◽

Functional Relevance ◽

H3 Acetylation ◽

Lower Production

Krüppel-like factor (KLF)-10 is an important transcriptional regulator of TGF-β1 signaling in both CD8+ and CD4+ T lymphocytes. In the present study, we demonstrate a novel role for KLF10 in the regulation of TGFβRII expression with functional relevance in macrophage differentiation and activation. We first show that transfer of KLF10−/− bone marrow-derived macrophages into wild-type (WT) mice leads to exacerbation of experimental colitis. At the cell biological level, using two phenotypic strategies, we show that KLF10-deficient mice have an altered colonic macrophage phenotype with higher frequency of proinflammatory LyC6+MHCII+ cells and a reciprocal decrease of the anti-inflammatory LyC6−MHCII+ subset. Additionally, the anti-inflammatory CD11b+CX3CR1hi subset of colonic macrophages is significantly decreased in KLF10−/− compared with WT mice under inflammatory conditions. Molecularly, CD11b+ colonic macrophages from KLF10−/− mice exhibit a proinflammatory cytokine profile with increased production of TNF-α and lower production of IL-10 in response to LPS stimulation. Because KLF10 is a transcription factor, we explored how this protein may regulate macrophage function. Consequently, we analyzed the expression of TGFβRII expression in colonic macrophages and found that, in the absence of KLF10, macrophages express lower levels of TGFβRII and display an attenuated Smad-2 phosphorylation following TGF-β1 stimulation. We further show that KLF10 directly binds to the TGFβRII promoter in macrophages, leading to enhanced gene expression through histone H3 acetylation. Collectively, our data reveal a critical role for KLF10 in the epigenetic regulation of TGFβRII expression in macrophages and the acquisition of a “regulatory” phenotype that contributes to intestinal mucosal homeostasis.

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GAS6 is a key homeostatic immunological regulator of host–commensal interactions in the oral mucosa

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1614926114 ◽

2017 ◽

Vol 114 (3) ◽

pp. E337-E346 ◽

Cited By ~ 34

Author(s):

Maria Nassar ◽

Yaara Tabib ◽

Tal Capucha ◽

Gabriel Mizraji ◽

Tsipora Nir ◽

...

Keyword(s):

Critical Role ◽

Anaerobic Bacteria ◽

Anaerobic Respiration ◽

Protein S ◽

Primary Response ◽

Oral Epithelium ◽

Oral Microbiota ◽

Microbial Dysbiosis ◽

Mucosal Homeostasis ◽

Activity Of Enzymes

The oral epithelium contributes to innate immunity and oral mucosal homeostasis, which is critical for preventing local inflammation and the associated adverse systemic conditions. Nevertheless, the mechanisms by which the oral epithelium maintains homeostasis are poorly understood. Here, we studied the role of growth arrest specific 6 (GAS6), a ligand of the TYRO3–AXL–MERTK (TAM) receptor family, in regulating oral mucosal homeostasis. Expression of GAS6 was restricted to the outer layers of the oral epithelium. In contrast to protein S, the other TAM ligand, which was constitutively expressed postnatally, expression of GAS6 initiated only 3–4 wk after birth. Further analysis revealed that GAS6 expression was induced by the oral microbiota in a myeloid differentiation primary response gene 88 (MyD88)-dependent fashion. Mice lacking GAS6 presented higher levels of inflammatory cytokines, elevated frequencies of neutrophils, and up-regulated activity of enzymes, generating reactive nitrogen species. We also found an imbalance in Th17/Treg ratio known to control tissue homeostasis, as Gas6-deficient dendritic cells preferentially secreted IL-6 and induced Th17 cells. As a result of this immunological shift, a significant microbial dysbiosis was observed in Gas6−/− mice, because anaerobic bacteria largely expanded by using inflammatory byproducts for anaerobic respiration. Using chimeric mice, we found a critical role for GAS6 in epithelial cells in maintaining oral homeostasis, whereas its absence in hematopoietic cells synergized the level of dysbiosis. We thus propose GAS6 as a key immunological regulator of host–commensal interactions in the oral epithelium.

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Antigen-Specific CD4+T Cell-Derived Gamma Interferon Is Both Necessary and Sufficient for ClearingChlamydiafrom the Small Intestine but Not the Large Intestine

Infection and Immunity ◽

10.1128/iai.00055-19 ◽

2019 ◽

Vol 87 (6) ◽

Cited By ~ 6

Author(s):

Hui Lin ◽

Conghui He ◽

John J. Koprivsek ◽

Jianlin Chen ◽

Zhiguang Zhou ◽

...

Keyword(s):

T Cells ◽

Small Intestine ◽

Gastrointestinal Tract ◽

T Cell ◽

Large Intestine ◽

Genital Tract ◽

Critical Role ◽

Gamma Interferon ◽

Content Type ◽

Ifn Γ

ABSTRACTThe genital tract pathogenChlamydia trachomatisis frequently detected in the gastrointestinal tract, but the host immunity that regulates chlamydial colonization in the gut remains unclear. In aChlamydia muridarum-C57 mouse model, chlamydial organisms are cleared from the genital tract in ∼4 weeks, but the genital organisms can spread to the gastrointestinal tract. We found that the gastrointestinal chlamydial organisms were cleared from the small intestine by day 28, paralleling their infection course in the genital tract, but persisted in the large intestine for long periods. Mice deficient in α/β T cells or CD4+T cells but not CD8+T cells showed chlamydial persistence in the small intestine, indicating a critical role for CD4+T cells in clearingChlamydiafrom the small intestine. The CD4+T cell-dependent clearance is likely mediated by gamma interferon (IFN-γ), since mice deficient in IFN-γ but not interleukin 22 (IL-22) signaling pathways rescued chlamydial colonization in the small intestine. Furthermore, exogenous IFN-γ was sufficient for clearingChlamydiafrom the small intestine but not the large intestine. Mice deficient in developingChlamydia-specific Th1 immunity showed chlamydial persistence in the small intestine. Finally, IFN-γ-producing CD4+but not CD8+T cells from immunized donor mice were sufficient for eliminatingChlamydiafrom the small intestine but not the large intestine of recipient mice. Thus, we have demonstrated a critical role for Th1 immunity in clearingChlamydiafrom the small intestine but not the large intestine, indicating that chlamydial colonization in different regions of the gastrointestinal tract is regulated by distinct immune mechanisms.

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Dexamethasone Effect on Embryonic Chick Respiratory Epithelium

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100053905 ◽

1982 ◽

Vol 40 ◽

pp. 248-249

Author(s):

M.R. Richter ◽

R.V. Blystone

Keyword(s):

Lung Development ◽

Critical Role ◽

Respiratory Epithelium ◽

Chick Embryos ◽

Embryonic Chick ◽

White Leghorn ◽

Lung Maturation ◽

Synthetic Analogs ◽

Lung Physiology ◽

Avian Lung

Dexamethasone and other synthetic analogs of corticosteroids have been employed clinically as enhancers of lung development. The mechanism(s) by which this steroid induction of later lung maturation operates is not clear. This study reports the effect on lung epithelia of dexamethasone administered at different intervals during development. White Leghorn chick embryos were used so as to remove possible maternal and placental influences on the exogenously applied steroid. Avian lung architecture does vary from mammals; however, respiratory surfactant produced by the lung epithelia serves an equally critical role in avian lung physiology.

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An atomic resolution study of a carbide phase in platinum

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100120503 ◽

1992 ◽

Vol 50 (1) ◽

pp. 20-21

Author(s):

M.J. Witcomb ◽

M.A. O'Keefe ◽

CJ. Echer ◽

C. Nelson ◽

J.H. Turner ◽

...

Keyword(s):

Solid Solution ◽

Carbon Atom ◽

Carbide Phase ◽

Structural Changes ◽

Critical Role ◽

Alloy System ◽

Atomic Resolution ◽

Excess Carbon ◽

Interstitial Carbon ◽

Resolution Study

Under normal circumstances, Pt dissolves only a very small amount of interstitial carbon in solid solution. Even so, an appropriate quench/age treatment leads to the formation of stable Pt2C {100} plate precipitates. Excess (quenched-in) vacancies play a critical role in the process by accommodating the volume and structural changes that accompany the transformation. This alloy system exhibits other interesting properties. Due to a large vacancy/carbon atom binding energy, Pt can absorb excess carbon at high temperatures in a carburizing atmosphere. In regions rich in carbon and vacancies, another carbide phase, Pt7C which undergoes an order-disorder reaction was formed. The present study of Pt carburized at 1160°C and aged at 515°C shows that other carbides in the PtxC series can be produced.

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