Biomedical subjects

Susan Gilfillan

Publications and source records attributed to Susan Gilfillan.

15 recordsLinked to original sources

PubMed2026

Brain perivascular macrophages regulate endothelial cell function via a cMAF-dependent transcriptional program in mouse and human.

Brain perivascular macrophages maintain brain physiology, yet their transcriptional regulators and functions in health and disease remain unclear. Using single-cell multi-omics and functional experiments, we identify cellular musculoaponeurotic fibrosarcoma oncogene (cMAF) as a key transcription factor for brain perivascular macrophages, and conditional deletion of cMAF disrupts their phenotype in vivo. Functionally, cMAF drives insulin-like growth factor-1 (IGF1) expression in perivascular macrophages, enabling communication with endothelial cells. Consistently, cMAF deletion in perivascular macrophages causes transcriptional alterations in cerebral arteries, affecting vascular functions. Notably, cMAF emerges as the main transcription factor for human perivascular macrophages, suggesting conservation of this transcriptional module. During Alzheimer's disease (AD), human perivascular macrophages upregulate cMAF and IGF1 to enhance communication with vascular cells, and this response is abrogated in APOE4 carriers. Lastly, we explore an uncharacterized polymorphism in cMAF, providing evidence that the cMAF program is protective against AD. Targeting cMAF in perivascular macrophages may offer new therapeutic strategies for neurodegenerative and cerebrovascular diseases.

APOE4↗

PubMed2024

Deficiency of IL-22-binding protein enhances the ability of the gut microbiota to protect against enteric pathogens.

Interleukin 22 (IL-22) promotes intestinal barrier integrity, stimulating epithelial cells to enact defense mechanisms against enteric infections, including the production of antimicrobial peptides. IL-22 binding protein (IL-22BP) is a soluble decoy encoded by the Il22ra2 gene that decreases IL-22 bioavailability, attenuating IL-22 signaling. The impact of IL-22BP on gut microbiota composition and functioning is poorly understood. We found that Il22ra2-/- mice are better protected against Clostridioides difficile and Citrobacter rodentium infections. This protection relied on IL-22-induced antimicrobial mechanisms before the infection occurred, rather than during the infection itself. Indeed, the gut microbiota of Il22ra2-/- mice mitigated infection of wild-type (WT) mice when transferred via cohousing or by cecal microbiota transplantation. Indicator species analysis of WT and Il22ra2-/- mice with and without cohousing disclosed that IL22BP deficiency yields a gut bacterial composition distinct from that of WT mice. Manipulation of dietary fiber content, measurements of intestinal short-chain fatty acids and oral treatment with acetate disclosed that resistance to C. difficile infection is related to increased production of acetate by Il22ra2-/--associated microbiota. Together, these findings suggest that IL-22BP represents a potential therapeutic target for those at risk for or with already manifest infection with this and perhaps other enteropathogens.

Animals↗

PubMed2015

Transcriptional programs define molecular characteristics of innate lymphoid cell classes and subsets.

The recognized diversity of innate lymphoid cells (ILCs) is rapidly expanding. Three ILC classes have emerged, ILC1, ILC2 and ILC3, with ILC1 and ILC3 including several subsets. The classification of some subsets is unclear, and it remains controversial whether natural killer (NK) cells and ILC1 cells are distinct cell types. To address these issues, we analyzed gene expression in ILCs and NK cells from mouse small intestine, spleen and liver, as part of the Immunological Genome Project. The results showed unique gene-expression patterns for some ILCs and overlapping patterns for ILC1 cells and NK cells, whereas other ILC subsets remained indistinguishable. We identified a transcriptional program shared by small intestine ILCs and a core ILC signature. We revealed and discuss transcripts that suggest previously unknown functions and developmental paths for ILCs.

Animals↗

PubMed2006

Cutting edge: TREM-2 attenuates macrophage activation.

The triggering receptor expressed on myeloid cells 2 (TREM-2) delivers intracellular signals through the adaptor DAP12 to regulate myeloid cell function both within and outside the immune system. The role of TREM-2 in immunity has been obscured by the failure to detect expression of the TREM-2 protein in vivo. In this study, we show that TREM-2 is expressed on macrophages infiltrating the tissues from the circulation and that alternative activation with IL-4 can induce TREM-2. TREM-2 expression is abrogated by macrophage maturation with LPS of IFN-gamma. Using TREM-2(-/-) mice, we find that TREM-2 functions to inhibit cytokine production by macrophages in response to the TLR ligands LPS, zymosan, and CpG. Furthermore, we find that TREM-2 completely accounts for the increased cytokine production previously reported by DAP12(-/-) macrophages. Taken together, these data show that TREM-2 is expressed on newly differentiated and alternatively activated macrophages and functions to restrain macrophage activation.

Adaptor Proteins, Signal Transducing↗

PubMed2006

Essential role of mda-5 in type I IFN responses to polyriboinosinic:polyribocytidylic acid and encephalomyocarditis picornavirus.

The innate immune system recognizes viral dsRNA through two distinct pathways; the Toll-like receptor 3 (TLR3) pathway detects dsRNA phagocytosed in endosomes; the helicases retinoic acid-induced protein I (RIG-I) and melanoma differentiation-associated gene-5 (mda-5) detect cytoplasmic dsRNA generated during viral replication. Both RIG-I and mda-5 can bind polyriboinosinic:polyribocytidylic acid (polyI:C), the synthetic analog of viral dsRNA, and mediate type I IFN responses to polyI:C and multiple RNA viruses in vitro. We generated mda-5-deficient mice and showed that mda-5 is the dominant receptor mediating type I IFN secretion in response to polyI:C in vitro and in vivo. Moreover, mda-5-/- mice exhibited a selectively impaired antiviral response to encephalomyocarditis picornavirus, indicating functional specialization of mda-5 in vivo.

Animals↗

PubMed2006

MR1-restricted V alpha 19i mucosal-associated invariant T cells are innate T cells in the gut lamina propria that provide a rapid and diverse cytokine response.

Mucosal-associated invariant T (MAIT) cells reside primarily in the gut lamina propria and require commensal flora for selection/expansion. They are restricted by the highly conserved MHC class I-related molecule MR1 and, like most NK T cells, express an invariant TCRalpha chain. Although they probably contribute to gut immunity, MAIT cells have not been functionally characterized because they are so rare. To create a model in which they are more abundant, we generated transgenic mice expressing only the TCRalpha chain (Valpha19i) that defines MAIT cells. By directly comparing Valpha19i transgenic mice on MR1+/+ and MR1-/- backgrounds, we were able to distinguish and characterize a population of Valpha19i T cells dependent on MR1 for development. MR1-restricted Valpha19i transgenic T cells recapitulate what is known about MAIT cell development. Furthermore, a relatively high proportion of transgenic MAIT cells express NK1.1, and most have a cell surface phenotype similar to that of Valpha14i NK T cells. Finally, MR1-restricted Valpha19i T cells secrete IFN-gamma, IL-4, IL-5, and IL-10 following TCR ligation, and we provide evidence for what may be two functionally distinct MAIT cell populations. These data strongly support the idea that MAIT cells contribute to the innate immune response in the gut mucosa.

Animals↗

PubMed2005

Phospholipase C-gamma 2 is a critical signaling mediator for murine NK cell activating receptors.

Phospholipase C-gamma (PLCgamma) is a key regulator of intracellular Ca(2+) mobilization. Two isoforms of PLCgamma have been identified, PLCgamma1 and PLCgamma2. Previously, in vitro studies indicated that activating NK cell receptors signal through both isoforms. However, PLCgamma2 deficiency alone was sufficient to induce a substantial impairment of NK cell-mediated cytotoxicity in vitro. Why PLCgamma2 is more important than PLCgamma1 for NK cell activation and whether PLCgamma2 is also critical for NK cell development, secretion of IFN-gamma, and clearance of viral infections in vivo is not known. In this study, we report that PLCgamma2 is the predominant isoform expressed in murine NK cells. PLCgamma2 deficiency did not affect NK cell numbers in bone marrow and spleen, but acquisition of Ly49 receptors by NK cells was partially impaired. PLCgamma2-deficient NK cells exhibited a dramatic impairment of cytolytic function and IFN-gamma production upon ligation of activating receptors, whereas they did secrete IFN-gamma in response to cytokines. Consequently, mice lacking PLCgamma2 controlled murine CMV infection substantially less effectively than did wild-type animals, and this defect was most evident in the spleen, where viral clearance mostly depends on NK cell lytic function. These results demonstrate that PLCgamma2 is crucial for development of the NK cell receptor repertoire and signaling of activating NK cell receptors, mediating optimal NK cell function in vivo.

Adaptor Proteins, Signal Transducing↗

PubMed2005

Evidence for MR1 antigen presentation to mucosal-associated invariant T cells.

The novel class Ib molecule MR1 is highly conserved in mammals, particularly in its alpha1/alpha2 domains. Recent studies demonstrated that MR1 expression is required for development and expansion of a small population of T cells expressing an invariant T cell receptor (TCR) alpha chain called mucosal-associated invariant T (MAIT) cells. Despite these intriguing properties it has been difficult to determine whether MR1 expression and MAIT cell recognition is ligand-dependent. To address these outstanding questions, monoclonal antibodies were produced in MR1 knock-out mice immunized with recombinant MR1 protein, and a series of MR1 mutations were generated at sites previously shown to disrupt the ability of class Ia molecules to bind peptide or TCR. Here we show that 1) MR1 molecules are detected by monoclonal antibodies in either an open or folded conformation that correlates precisely with peptide-induced conformational changes in class Ia molecules, 2) only the folded MR1 conformer activated 2/2 MAIT hybridoma cells tested, 3) the pattern of MAIT cell activation by the MR1 mutants implies the MR1/TCR orientation is strikingly similar to published major histocompatibility complex/alphabetaTCR engagements, 4) all the MR1 mutations tested and found to severely reduce surface expression of folded molecules were located in the putative ligand binding groove, and 5) certain groove mutants of MR1 that are highly expressed on the cell surface disrupt MAIT cell activation. These combined data strongly support the conclusion that MR1 has an antigen presentation function.

Animals↗

PubMed2005

Mucosal-associated invariant T (MAIT) cells: an evolutionarily conserved T cell subset.

Besides mainstream TCRalphabeta T cells harboring a very diverse repertoire, two subsets display an evolutionarily conserved invariant repertoire. This striking conservation indicates important and unique functions. CD1d-restricted NK-T cells expressing an invariant Valpha14 TCRalpha chain have been implicated in microbial and tumor responses as well as in auto-immunity. In this review, we describe the other subset, which bears the canonical hValpha7.2/mValpha19-Jalpha33 TCRalpha chain paired with a restricted set of Vbeta segments. These invariant T cells are present in mice, humans and cattle. They are preferentially located in the gut lamina propria (LP) of humans and mice and are therefore called mucosal-associated invariant T (MAIT) cells. Selection/expansion of this population requires B lymphocytes expressing MR1, a monomorphic major histocompatibility complex class I-related molecule that is also strikingly conserved in diverse mammalian species. MAIT cells are not present in germ-free mice, indicating that commensal flora is required for their expansion in the gut LP. The nature of the ligand and the putative functions of these MAIT cells are discussed.

Animals↗

PubMed2003

Biochemical features of the MHC-related protein 1 consistent with an immunological function.

MHC-related protein (MR)1 is an MHC class I-related molecule encoded on chromosome 1 that is highly conserved among mammals and is more closely related to classical class I molecules than are other nonclassical class I family members. In this report, we show for the first time that both mouse and human MR1 molecules can associate with the peptide-loading complex and can be detected at low levels at the surface of transfected cells. We also report the production of recombinant human MR1 molecules in insect cells using highly supplemented media and provide evidence that the MR1 H chain can assume a folded conformation and is stoichiometrically associated with beta(2)-microglobulin, similar to class I molecules. Cumulatively, these findings demonstrate that surface expression of MR1 is possible but may be limited by a specific ligand or associated molecule.

Amino Acid Sequence↗

PubMed2003

Selection of evolutionarily conserved mucosal-associated invariant T cells by MR1.

The evolutionary conservation of T lymphocyte subsets bearing T-cell receptors (TCRs) using invariant alpha-chains is indicative of unique functions. CD1d-restricted natural killer T (NK-T) cells that express an invariant Valpha14 TCRalpha chain have been implicated in microbial and tumour responses, as well as in auto-immunity. Here we show that T cells that express the canonical hValpha7.2-Jalpha33 or mValpha19-Jalpha33 TCR rearrangement are preferentially located in the gut lamina propria of humans and mice, respectively, and are therefore genuine mucosal-associated invariant T (MAIT) cells. Selection and/or expansion of this population requires B lymphocytes, as MAIT cells are absent in B-cell-deficient patients and mice. In addition, we show that MAIT cells are selected and/or restricted by MR1, a monomorphic major histocompatibility complex class I-related molecule that is markedly conserved in diverse mammalian species. MAIT cells are not present in germ-free mice, indicating that commensal flora is required for their expansion in the gut lamina propria. This indicates that MAIT cells are probably involved in the host response at the site of pathogen entry, and may regulate intestinal B-cell activity.

Amino Acid Sequence↗

PubMed2002

NKG2D recruits two distinct adapters to trigger NK cell activation and costimulation.

NKG2D is a receptor on natural killer (NK) cells and cytotoxic T lymphocytes that binds major histocompatibility complex (MHC) class I-like ligands expressed primarily on virally infected and neoplastic cells. In vitro studies indicate that NKG2D provides costimulation through an associated adapter, DAP10, which recruits phosphatidylinositol-3 kinase. Here we show that in DAP10-deficient mice, CD8+ T cells lack NKG2D expression and are incapable of mounting tumor-specific responses. However, DAP10-deficient NK cells express a functional NKG2D receptor due to the association of NKG2D with another adapter molecule, DAP12 (also known as KARAP), which recruits protein tyrosine kinases. Thus, NKG2D is a versatile receptor that, depending on the availability of adapter partners, mediates costimulation in T cells and/or activation in NK cells.

Adaptor Proteins, Signal Transducing↗

PubMed2002

A cluster of ten novel MHC class I related genes on human chromosome 6q24.2-q25.3.

We have identified a novel family of human major histocompatibility complex (MHC) class I genes. This MHC class I related gene family is defined by 10 members, among which 6 encode potentially functional glycoproteins. The 180-kb cluster containing them has been generated by serial duplication and minimal diversification of an ancestral prototype. They are not located within the MHC on 6p21.3, but near the tip of its long arm at q24.2-q25.3, close to the human equivalent of the mouse H2-linked t-complex, a subchromosomal region syntenic to a segment of mouse chromosome 10 harboring the orthologous MHC class I related retinoic acid early transcript loci, Raet1a-d. Hence we have named the identified loci RAET1E-N. Human RAET1 products are all devoid of the membrane-proximal immunoglobulin-like alpha3 domain and most, but not all, are predicted to remain membrane-anchored via glycosylphosphatidylinositol linkage and are shown to display an atypical pattern of polymorphism. RAET1 transcripts are absent from hematopoietic tissues, but largely expressed in tumors. The involvement of orthologous mouse RAET1A-D/H60 in natural killer and T-cell activation through NKG2D engagement augurs a similar function for the human RAET1 proteins.

Animals↗

PubMed2002

Inactivation of the hemochromatosis gene differentially regulates duodenal expression of iron-related mRNAs between mouse strains.

BACKGROUND & AIMS: Hfe knockout mice, like patients with hereditary hemochromatosis, have augmented duodenal iron absorption and increased iron deposition in hepatic parenchymal cells. The goals of the present study were to gain further insight into the control of iron absorption by comparing the transcript levels of iron-related genes in the duodenum of DBA/2 Hfe-/- mice, susceptible to iron loading, and wild-type controls, and to test whether variations in the duodenal expression of these messengers contribute to the DBA/2 and C57BL/6 strain differences in the severity of hepatic iron loading. METHODS: Expression of the different transcripts was quantified by real-time polymerase chain reaction. RESULTS: The 2 strains differ strikingly, not only in the severity of hepatic iron loading, but also in the duodenal expression of iron-related genes. In DBA/2 Hfe-/- mice, increased intestinal iron absorption results from the concomitant up-regulation of the Dcytb, DMT1, and FPN1 messengers. No increase in the expression of these messengers is seen in C57BL/6 Hfe-/- mice. CONCLUSIONS: The up-regulation of these transcripts suggests that an inappropriate iron-deficiency signal is sensed by the duodenal enterocytes, leading to an enhanced ferric reductase activity and the increase of duodenal iron uptake and transfer to the circulation. The genes modifying the hemochromatosis phenotype probably act by modifying the expression of these 3 messengers.

Animals↗

PubMedDate not supplied

Iron overload in mice expressing HFE exclusively in the intestinal villi provides evidence that HFE regulates a functional cross-talk between crypt and villi enterocytes.

Hereditary hemochromatosis (HH), a common autosomal recessive disorder due to a mutation in HFE, which encodes an atypical MHC class I glycoprotein, is characterized by excessive absorption of dietary iron. Little is known however of the apparently complex pathophysiology of HFE involvement in the process of iron influx. Here, in order to tackle the issue in vivo, we decided to target HFE expression exclusively to the relevant tissue, intestinal epithelium. This was achieved by putting HFE under transcriptional control of the rat fatty acid binding protein (Fabpi) promoter. Quite unexpectedly, Fabpi-HFE mice had significantly elevated serum transferrin saturation levels in comparison to those of normal littermates. By a careful, layer by layer analysis of transgene expression along the crypt-villus axis, we were able to affirm that the ectopic expression of transgenic HFE in the differentiated villi enterocytes was responsible for ferric hyperabsorption, a phenomenon exacerbated in the absence of endogenous HFE expression, which we assessed by crossing the transgene onto an HFE(-/-) (knockout) background. This forced dichotomy between the absence of HFE in the crypt and expression in the villi provides experimental support that HFE functions as a "gatekeeper," regulating the cross-talk between the crypt and villi enterocytes and thereby modulating the avidity of mature enterocytes for dietary iron.

Animals↗