Gene coexpression networks reveal a broad role for lncRNAs in inflammatory bowel disease.

The role of long noncoding RNAs (lncRNAs) in disease is incompletely understood, but their regulation of inflammation is increasingly appreciated. We addressed the extent of lncRNA involvement in inflammatory bowel disease (IBD) using biopsy-derived RNA-sequencing data from a large cohort of deeply phenotyped patients with IBD. Weighted gene correlation network analysis revealed gene modules of lncRNAs coexpressed with protein-coding genes enriched for biological pathways, correlated with epithelial and immune cell signatures, or correlated with distal colon expression. Correlation of modules with clinical features uncovered a module correlated with disease severity, with an enriched interferon response signature containing the hub lncRNA IRF1-AS1. Connecting genes to IBD-associated single nucleotide polymorphisms (SNPs) revealed an enrichment of SNP-adjacent lncRNAs in biologically relevant modules. Ulcerative colitis-specific SNPs were enriched in distal colon-related modules, suggesting that disease-specific mechanisms may result from altered lncRNA expression. The function of the IBD-associated SNP-adjacent lncRNA IRF1-AS1 was explored in human myeloid cells, and our results suggested IRF1-AS1 promoted optimal production of TNF-α, IL-6, and IL-23. A CRISPR/Cas9-mediated activation screen in THP-1 cells revealed several lncRNAs that modulated LPS-induced TNF-α responses. Overall, this study uncovered the expression patterns of lncRNAs in IBD that identify functional, disease-relevant lncRNAs.

The lncRNA HOXA11os regulates mitochondrial function in myeloid cells to maintain intestinal homeostasis.

This study reveals a previously uncharacterized mechanism to restrict intestinal inflammation via a regulatory RNA transcribed from a noncoding genomic locus. We identified a novel transcript of the lncRNA HOXA11os specifically expressed in the distal colon that is reduced to undetectable levels in colitis. HOXA11os is localized to mitochondria under basal conditions and interacts with a core subunit of complex 1 of the electron transport chain (ETC) to maintain its activity. Deficiency of HOXA11os in colonic myeloid cells results in complex I deficiency, dysfunctional oxidative phosphorylation (OXPHOS), and the production of mitochondrial reactive oxygen species (mtROS). As a result, HOXA11os-deficient mice develop spontaneous intestinal inflammation and are hypersusceptible to colitis. Collectively, these studies identify a new regulatory axis whereby a lncRNA maintains intestinal homeostasis and restricts inflammation in the colon through the regulation of complex I activity.

IFN-γR/STAT1 signaling in recipient hematopoietic antigen-presenting cells suppresses graft-versus-host disease.

The absence of IFN-γ receptor (IFN-γR) or STAT1 signaling in donor cells has been shown to result in reduced induction of acute graft-versus-host disease (GVHD). In this study, we unexpectedly observed increased activation and expansion of donor lymphocytes in both lymphohematopoietic organs and GVHD target tissues of IFN-γR/STAT1-deficient recipient mice, leading to rapid mortality following the induction of GVHD. LPS-matured, BM-derived Ifngr1-/- Stat1-/- DCs (BMDCs) were more potent allogeneic stimulators and expressed increased levels of MHC II and costimulatory molecules. Similar effects were observed in human antigen-presenting cells (APCs) with knockdown of Stat1 by CRISPR/Cas9 and treatment with a JAK1/2 inhibitor. Furthermore, we demonstrated that the absence of IFN-γR/STAT1 signaling in hematopoietic APCs impaired the presentation of exogenous antigens, while promoting the presentation of endogenous antigens. Thus, the indirect presentation of host antigens to donor lymphocytes was defective in IFN-γR/STAT1-deficient, donor-derived APCs in fully donor chimeric mice. The differential effects of IFN-γR/STAT1 signaling on endogenous and exogenous antigen presentation could provide further insight into the roles of the IFN-γ/STAT1 signaling pathway in the pathogenesis of GVHD, organ rejection, and autoimmune diseases.

The lncRNA LUCAT1 is elevated in inflammatory disease and restrains inflammation by regulating the splicing and stability of NR4A2.

The nuclear long non-coding RNA LUCAT1 has previously been identified as a negative feedback regulator of type I interferon and inflammatory cytokine expression in human myeloid cells. Here, we define the mechanistic basis for the suppression of inflammatory gene expression by LUCAT1. Using comprehensive identification of RNA-binding proteins by mass spectrometry as well as RNA immunoprecipitation, we identified proteins important in processing and alternative splicing of mRNAs as LUCAT1-binding proteins. These included heterogeneous nuclear ribonucleoprotein C, M, and A2B1. Consistent with this finding, cells lacking LUCAT1 have altered splicing of selected immune genes. In particular, upon lipopolysaccharide stimulation, the splicing of the nuclear receptor 4A2 (NR4A2) gene was particularly affected. As a consequence, expression of NR4A2 was reduced and delayed in cells lacking LUCAT1. NR4A2-deficient cells had elevated expression of immune genes. These observations suggest that LUCAT1 is induced to control the splicing and stability of NR4A2, which is in part responsible for the anti-inflammatory effect of LUCAT1. Furthermore, we analyzed a large cohort of patients with inflammatory bowel disease as well as asthma and chronic obstructive pulmonary disease. In these patients, LUCAT1 levels were elevated and in both diseases, positively correlated with disease severity. Collectively, these studies define a key molecular mechanism of LUCAT1-dependent immune regulation through post-transcriptional regulation of mRNAs highlighting its role in the regulation of inflammatory disease.

PIR-B Regulates CD4+ IL17a+ T-Cell Survival and Restricts T-Cell-Dependent Intestinal Inflammatory Responses.

BACKGROUND & AIMS: CD4+ T cells are regulated by activating and inhibitory cues, and dysregulation of these proper regulatory inputs predisposes these cells to aberrant inflammation and exacerbation of disease. We investigated the role of the inhibitory receptor paired immunoglobulin-like receptor B (PIR-B) in the regulation of the CD4+ T-cell inflammatory response and exacerbation of the colitic phenotype. METHODS: We used Il10-/- spontaneous and CD4+CD45RBhi T-cell transfer models of colitis with PIR-B-deficient (Pirb-/-) mice. Flow cytometry, Western blot, and RNA sequencing analysis was performed on wild-type and Pirb-/- CD4+ T cells. In silico analyses were performed on RNA sequencing data set of ileal biopsy samples from pediatric CD and non-inflammatory bowel disease patients and sorted human memory CD4+ T cells. RESULTS: We identified PIR-B expression on memory CD4+ interleukin (IL)17a+ cells. We show that PIR-B regulates CD4+ T-helper 17 cell (Th17)-dependent chronic intestinal inflammatory responses and the development of colitis. Mechanistically, we show that the PIR-B- Src-homology region 2 domain-containing phosphatase-1/2 axis tempers mammalian target of rapamycin complex 1 signaling and mammalian target of rapamycin complex 1-dependent caspase-3/7 apoptosis, resulting in CD4+ IL17a+ cell survival. In silico analyses showed enrichment of transcriptional signatures for Th17 cells (RORC, RORA, and IL17A) and tissue resident memory (HOBIT, IL7R, and BLIMP1) networks in PIR-B+ murine CD4+ T cells and human CD4+ T cells that express the human homologue leukocyte immunoglobulin-like receptor subfamily B member 3 (LILRB3). High levels of LILRB3 expression were associated strongly with mucosal injury and a proinflammatory Th17 signature, and this signature was restricted to a treatment-naïve, severe pediatric CD population. CONCLUSIONS: Our findings show an intrinsic role for PIR-B/LILRB3 in the regulation of CD4+ IL17a+ T-cell pathogenic memory responses.

GIMAP5 maintains liver endothelial cell homeostasis and prevents portal hypertension.

Portal hypertension is a major contributor to decompensation and death from liver disease, a global health problem. Here, we demonstrate homozygous damaging mutations in GIMAP5, a small organellar GTPase, in four families with unexplained portal hypertension. We show that GIMAP5 is expressed in hepatic endothelial cells and that its loss in both humans and mice results in capillarization of liver sinusoidal endothelial cells (LSECs); this effect is also seen when GIMAP5 is selectively deleted in endothelial cells. Single-cell RNA-sequencing analysis in a GIMAP5-deficient mouse model reveals replacement of LSECs with capillarized endothelial cells, a reduction of macrovascular hepatic endothelial cells, and places GIMAP5 upstream of GATA4, a transcription factor required for LSEC specification. Thus, GIMAP5 is a critical regulator of liver endothelial cell homeostasis and, when absent, produces portal hypertension. These findings provide new insight into the pathogenesis of portal hypertension, a major contributor to morbidity and mortality from liver disease.

The Variable Genomic NK Cell Receptor Locus Is a Key Determinant of CD4+ T Cell Responses During Viral Infection.

Increasing evidence points to a key role for NK cells in controlling adaptive immune responses. In studies examining the role of CD1d on CD4+ T cell responses, we found that a line of CD1d-deficient mice on the C57BL/6J background had a homozygous 129 locus on chromosome 6 containing the entire NK cell gene cluster. Mice possessing this locus (C57BL/6.NKC129) displayed a >10-fold reduction in antigen-specific CD4+ T cell responses after intracranial infection with lymphocytic choriomeningitis virus (LCMV). Neither parental strain displayed defects in viral-specific CD4+ T cell responses. Interestingly, following infection, increased numbers of NK cells accumulated in the lymph nodes of C57BL/6.NKC129 mice and displayed enhanced in vivo functionality. Moreover, depletion of NK cells with anti-asialo-GM-1 antibody in C57BL/6.NKC129 mice resulted in a >20-fold increase in viral-specific CD4+ T cell responses. Mechanistically, we found that dendritic cell antigen presentation and early type I IFN production were significantly decreased in C57BL/6.NKC129 mice, but were restored in perforin-deficient C57BL/6.NKC129 mice or following NK depletion. Together, these data reveal that the variable genomic regions containing the activating/inhibitory NK cell receptors are key determinants of antigen-specific CD4+ T cell responses, controlling type I IFN production and the antigen-presenting capacity of dendritic cells.

CD244 represents a new therapeutic target in head and neck squamous cell carcinoma.

BACKGROUND: Developing novel strategies to overcome the immunosuppressive tumor microenvironment is a critically important area of cancer therapy research. Here, we assess the therapeutic potential of CD244 (2B4/signaling lymphocyte activation molecule family 4), an immunoregulatory receptor found on a variety of immune cells, including exhausted CD8+ T cells, dendritic cells (DCs), and myeloid-derived suppressor cells (MDSCs). METHODS: Using de-identified human tumor and blood samples from patients with head and neck squamous cell carcinoma (HNSCC) and HNSCC models in WT and CD244-/- mice, we assessed the therapeutic potential of CD244 using flow cytometry, RT-PCR, Luminex immunoassays and histopathological analyses. RESULTS: Compared with healthy tissues, tumor infiltrating CD8+ T cells from HNSCC patients and a HNSCC mouse model showed significant increased expression of CD244 expression that correlated with PD1 expression. Moreover, CD244 was increased on intratumoral DC and MDSC and high CD244 expression correlated with PD-L1 expression and increased spontaneous expression of immune-suppressive mediators. In addition, CD244 activation inhibited production of proinflammatory cytokines in human DC in vitro. Importantly, CD244-/- mice showed significantly impaired tumor growth of HNSCC and interventional treatment of WT mice with anti-CD244 monoclonal antibody significantly impaired the growth of established HNSCC tumors and increased tumor-infiltrating CD8+ T cells. CONCLUSIONS: Together these data suggest that CD244 contributes to the overall immune-suppressive environment and therefore has potential as a new immunotherapy target in the treatment of malignancies.

Resolution of herpes simplex virus reactivation in vivo results in neuronal destruction.

A fundamental question in herpes simplex virus (HSV) pathogenesis is the consequence of viral reactivation to the neuron. Evidence supporting both post-reactivation survival and demise is published. The exceedingly rare nature of this event at the neuronal level in the sensory ganglion has limited direct examination of this important question. In this study, an in-depth in vivo analysis of the resolution of reactivation was undertaken. Latently infected C57BL/6 mice were induced to reactivate in vivo by hyperthermic stress. Infectious virus was detected in a high percentage (60-80%) of the trigeminal ganglia from these mice at 20 hours post-reactivation stimulus, but declined by 48 hours post-stimulus (0-13%). With increasing time post-reactivation stimulus, the percentage of reactivating neurons surrounded by a cellular cuff increased, which correlated with a decrease in detectable infectious virus and number of viral protein positive neurons. Importantly, in addition to intact viral protein positive neurons, fragmented viral protein positive neurons morphologically consistent with apoptotic bodies and containing cleaved caspase-3 were detected. The frequency of this phenotype increased through time post-reactivation. These fragmented neurons were surrounded by Iba1+ cells, consistent with phagocytic removal of dead neurons. Evidence of neuronal destruction post-reactivation prompted re-examination of the previously reported non-cytolytic role of T cells in controlling reactivation. Latently infected mice were treated with anti-CD4/CD8 antibodies prior to induced reactivation. Neither infectious virus titers nor neuronal fragmentation were altered. In contrast, when viral DNA replication was blocked during reactivation, fragmentation was not observed even though viral proteins were expressed. Our data demonstrate that at least a portion of reactivating neurons are destroyed. Although no evidence for direct T cell mediated antigen recognition in this process was apparent, inhibition of viral DNA replication blocked neuronal fragmentation. These unexpected findings raise new questions about the resolution of HSV reactivation in the host nervous system.

Type I IFN Drives Experimental Systemic Lupus Erythematosus by Distinct Mechanisms in CD4 T Cells and B Cells.

Myriad studies have linked type I IFN to the pathogenesis of autoimmune diseases, including systemic lupus erythematosus (SLE). Although increased levels of type I IFN are found in patients with SLE, and IFN blockade ameliorates disease in many mouse models of lupus, its precise roles in driving SLE pathogenesis remain largely unknown. In this study, we dissected the effect of type I IFN sensing by CD4 T cells and B cells on the development of T follicular helper cells (TFH), germinal center (GC) B cells, plasmablasts, and antinuclear dsDNA IgG levels using the bm12 chronic graft-versus-host disease model of SLE-like disease. Type I IFN sensing by B cells decreased their threshold for BCR signaling and increased their expression of MHC class II, CD40, and Bcl-6, requirements for optimal GC B cell functions. In line with these data, ablation of type I IFN sensing in B cells significantly reduced the accumulation of GC B cells, plasmablasts, and autoantibodies. Ablation of type I IFN sensing in T cells significantly inhibited TFH expansion and subsequent B cell responses. In contrast to the effect in B cells, type I IFN did not promote proliferation in the T cells but protected them from NK cell-mediated killing. Consequently, ablation of either perforin or NK cells completely restored TFH expansion of IFNAR-/- TFH and, subsequently, restored the B cell responses. Together, our data provide evidence for novel roles of type I IFN and immunoregulatory NK cells in the context of sterile inflammation and SLE-like disease.

Gab3 is required for IL-2- and IL-15-induced NK cell expansion and limits trophoblast invasion during pregnancy.

The scaffolding protein Grb2-associated binding protein 3 (Gab3) is a member of the Gab family, whose functions have remained elusive. Here, we identify Gab3 as a key determinant of peripheral NK cell expansion. Loss of Gab3 resulted in impaired IL-2 and IL-15-induced NK cell priming and expansion due to a selective impairment in MAPK signaling but not STAT5 signaling. In vivo, we found that Gab3 is required for recognition and elimination of "missing-self" and tumor targets. Unexpectedly, our studies also revealed that Gab3 plays an important role during pregnancy. Gab3-deficient mice exhibited impaired uterine NK cell expansion associated with abnormal spiral artery remodeling and increased trophoblast invasion in the decidua basalis. This coincided with stillbirth, retained placenta, maternal hemorrhage, and undelivered fetoplacental units at term. Thus, Gab3 is a key component required for cytokine-mediated NK cell priming and expansion that is essential for antitumor responses and limits trophoblast cell invasion during pregnancy.

Loss of GTPase of immunity-associated protein 5 (Gimap5) promotes pathogenic CD4+ T-cell development and allergic airway disease.

BACKGROUND: GTPase of immunity-associated protein 5 (GIMAP5) is essential for lymphocyte homeostasis and survival. Recently, human GIMAP5 single nucleotide polymorphisms have been linked to an increased risk for asthma, whereas loss of Gimap5 in mice has been associated with severe CD4+ T cell-driven immune pathology. OBJECTIVE: We sought to identify the molecular and cellular mechanisms by which Gimap5 deficiency predisposes to allergic airway disease. METHODS: CD4+ T-cell polarization and development of pathogenic CD4+ T cells were assessed in Gimap5-deficient mice and a human patient with a GIMAP5 loss-of-function (LOF) mutation. House dust mite-induced airway inflammation was assessed by using a complete Gimap5 LOF (Gimap5sph/sph) and conditional Gimap5fl/flCd4Cre/ert2 mice. RESULTS: GIMAP5 LOF mutations in both mice and human subjects are associated with spontaneous polarization toward pathogenic TH17 and TH2 cells in vivo. Mechanistic studies in vitro reveal that impairment of Gimap5-deficient TH cell differentiation is associated with increased DNA damage, particularly during TH1-polarizing conditions. DNA damage in Gimap5-deficient CD4+ T cells could be controlled by TGF-ß, thereby promoting TH17 polarization. When challenged with house dust mite in vivo, Gimap5-deficient mice displayed an exacerbated asthma phenotype (inflammation and airway hyperresponsiveness), with increased development of TH2, TH17, and pathogenic TH17/TH2 cells. CONCLUSION: Activation of Gimap5-deficient CD4+ T cells is associated with increased DNA damage and reduced survival that can be overcome by TGF-ß. This leads to selective survival of pathogenic TH17 cells but also TH2 cells in human subjects and mice, ultimately promoting allergic airway disease.

The Emerging Role of CD244 Signaling in Immune Cells of the Tumor Microenvironment.

In cancer, immune exhaustion contributes to the immunosuppressive tumor microenvironment. Exhausted immune cells demonstrate poor effector function and sustained expression of certain immunomodulatory receptors, which can be therapeutically targeted. CD244 is a Signaling Lymphocyte Activation Molecule (SLAM) family immunoregulatory receptor found on many immune cell types-including NK cells, a subset of T cells, DCs, and MDSCs-that represents a potential therapeutic target. Here, we discuss the role of CD244 in tumor-mediated immune cell regulation.

Peroxisomal ß-oxidation regulates whole body metabolism, inflammatory vigor, and pathogenesis of nonalcoholic fatty liver disease.

Nonalcoholic fatty liver disease (NAFLD), a metabolic predisposition for development of hepatocellular carcinoma (HCC), represents a disease spectrum ranging from steatosis to steatohepatitis to cirrhosis. Acox1, a rate-limiting enzyme in peroxisomal fatty acid ß-oxidation, regulates metabolism, spontaneous hepatic steatosis, and hepatocellular damage over time. However, it is unknown whether Acox1 modulates inflammation relevant to NAFLD pathogenesis or if Acox1-associated metabolic and inflammatory derangements uncover and accelerate potential for NAFLD progression. Here, we show that mice with a point mutation in Acox1 (Acox1Lampe1) exhibited altered cellular metabolism, modified T cell polarization, and exacerbated immune cell inflammatory potential. Further, in context of a brief obesogenic diet stress, NAFLD progression associated with Acox1 mutation resulted in significantly accelerated and exacerbated hepatocellular damage via induction of profound histological changes in hepatocytes, hepatic inflammation, and robust upregulation of gene expression associated with HCC development. Collectively, these data demonstrate that ß-oxidation links metabolism and immune responsiveness and that a better understanding of peroxisomal ß-oxidation may allow for discovery of mechanisms central for NAFLD progression.

Gimap5-dependent inactivation of GSK3ß is required for CD4+ T cell homeostasis and prevention of immune pathology.

GTPase of immunity-associated protein 5 (Gimap5) is linked with lymphocyte survival, autoimmunity, and colitis, but its mechanisms of action are unclear. Here, we show that Gimap5 is essential for the inactivation of glycogen synthase kinase-3ß (GSK3ß) following T cell activation. In the absence of Gimap5, constitutive GSK3ß activity constrains c-Myc induction and NFATc1 nuclear import, thereby limiting productive CD4+ T cell proliferation. Additionally, Gimap5 facilitates Ser389 phosphorylation and nuclear translocation of GSK3ß, thereby limiting DNA damage in CD4+ T cells. Importantly, pharmacological inhibition and genetic targeting of GSK3ß can override Gimap5 deficiency in CD4+ T cells and ameliorates immunopathology in mice. Finally, we show that a human patient with a GIMAP5 loss-of-function mutation has lymphopenia and impaired T cell proliferation in vitro that can be rescued with GSK3 inhibitors. Given that the expression of Gimap5 is lymphocyte-restricted, we propose that its control of GSK3ß is an important checkpoint in lymphocyte proliferation.

An ENU-induced splice site mutation of mouse Col1a1 causing recessive osteogenesis imperfecta and revealing a novel splicing rescue.

GU-AG consensus sequences are used for intron recognition in the majority of cases of pre-mRNA splicing in eukaryotes. Mutations at splice junctions often cause exon skipping, short deletions, or insertions in the mature mRNA, underlying one common molecular mechanism of genetic diseases. Using N-ethyl-N-nitrosourea, a novel recessive mutation named seal was produced, associated with fragile bones and susceptibility to fractures (spine and limbs). A single nucleotide transversion (T → A) at the second position of intron 36 of the Col1a1 gene, encoding the type I collagen, α1 chain, was responsible for the phenotype. Col1a1 seal mRNA expression occurred at greatly reduced levels compared to the wild-type transcript, resulting in reduced and aberrant collagen fibers in tibiae of seal homozygous mice. Unexpectedly, splicing of Col1a1 seal mRNA followed the normal pattern despite the presence of the donor splice site mutation, likely due to the action of a putative intronic splicing enhancer present in intron 25, which appeared to function redundantly with the splice donor site of intron 36. Seal mice represent a model of human osteogenesis imperfecta, and reveal a previously unknown mechanism for splicing "rescue."

Type I interferons regulate susceptibility to inflammation-induced preterm birth.

Preterm birth (PTB) is a leading worldwide cause of morbidity and mortality in infants. Maternal inflammation induced by microbial infection is a critical predisposing factor for PTB. However, biological processes associated with competency of pathogens, including viruses, to induce PTB or sensitize for secondary bacterial infection-driven PTB are unknown. We show that pathogen/pathogen-associated molecular pattern-driven activation of type I IFN/IFN receptor (IFNAR) was sufficient to prime for systemic and uterine proinflammatory chemokine and cytokine production and induction of PTB. Similarly, treatment with recombinant type I IFNs recapitulated such effects by exacerbating proinflammatory cytokine production and reducing the dose of secondary inflammatory challenge required for induction of PTB. Inflammatory challenge-driven induction of PTB was eliminated by defects in type I IFN, TLR, or IL-6 responsiveness, whereas the sequence of type I IFN sensing by IFNAR on hematopoietic cells was essential for regulation of proinflammatory cytokine production. Importantly, we also show that type I IFN priming effects are conserved from mice to nonhuman primates and humans, and expression of both type I IFNs and proinflammatory cytokines is upregulated in human PTB. Thus, activation of the type I IFN/IFNAR axis in pregnancy primes for inflammation-driven PTB and provides an actionable biomarker and therapeutic target for mitigating PTB risk.

Myeloid-derived NF-κB negative regulation of PU.1 and c/EBP-ß-driven pro-inflammatory cytokine production restrains LPS-induced shock.

Sepsis is a life-threatening event predominantly caused by Gram-negative bacteria. Bacterial infection causes a pronounced macrophage (MΦ) and dendritic cell activation that leads to excessive pro-inflammatory cytokine IL-1ß, IL-6 and TNF-α production (cytokine storm), resulting in endotoxic shock. Previous experimental studies have revealed that inhibiting NF-κB signaling ameliorates disease symptoms; however, the contribution of myeloid p65 in endotoxic shock remains elusive. In this study, we demonstrate increased mortality in mice lacking p65 in the myeloid lineage (p65Δmye) compared with wild type mice upon ultra-pure LPS challenge. We show that increased susceptibility to LPS-induced shock was associated with elevated serum level of IL-1ß and IL-6. Mechanistic analyses revealed that LPS-induced pro-inflammatory cytokine production was ameliorated in p65-deficient bone marrow-derived MΦs; however, p65-deficient 'activated' peritoneal MΦs exhibited elevated IL-1ß and IL-6. We show that the elevated pro-inflammatory cytokine secretion was due, in part, to increased accumulation of IL-1ß mRNA and protein in activated inflammatory MΦs. The increased IL-1ß was linked with heightened binding of PU.1 and CCAAT/enhancer binding protein-ß to Il1b and Il6 promoters in activated inflammatory MΦs. Our data provide insight into a role for NF-κB in the negative regulation of pro-inflammatory cytokines in myeloid cells.

A mutation within the SH2 domain of slp-76 regulates the tissue distribution and cytokine production of iNKT cells in mice.

TCR ligation is critical for the selection, activation, and integrin expression of T lymphocytes. Here, we explored the role of the TCR adaptor protein slp-76 on iNKT-cell biology. Compared to B6 controls, slp-76(ace/ace) mice carrying a missense mutation (Thr428Ile) within the SH2-domain of slp-76 showed an increase in iNKT cells in the thymus and lymph nodes, but a decrease in iNKT cells in spleens and livers, along with reduced ADAP expression and cytokine response. A comparable reduction in iNKT cells was observed in the livers and spleens of ADAP-deficient mice. Like ADAP(-/-) iNKT cells, slp-76(ace/ace) iNKT cells were characterized by enhanced CD11b expression, correlating with an impaired induction of the TCR immediate-early gene Nur77 and a decreased adhesion to ICAM-1. Furthermore, CD11b-intrinsic effects inhibited cytokine release, concanavalin A-mediated inflammation, and iNKT-cell accumulation in the liver. Unlike B6 and ADAP(-/-) mice, the expression of the transcription factors Id3 and PLZF was reduced, whereas NP-1-expression was enhanced in slp-76(ace/ace) mice. Blockade of NP-1 decreased the recovery of iNKT cells from peripheral lymph nodes, identifying NP-1 as an iNKT-cell-specific adhesion factor. Thus, slp-76 contributes to the regulation of the tissue distribution, PLZF, and cytokine expression of iNKT cells via ADAP-dependent and -independent mechanisms.

TCR and IL-7 Signaling Are Altered in the Absence of Functional GTPase of the Immune Associated Nucleotide Binding Protein 5 (GIMAP5).

GTPase of the immune associated nucleotide binding protein (GIMAP) family of proteins are expressed essentially in cells of the hematopoietic system. Mutation in the founding member of this gene family, Gimap5, results in the lymphopenic phenotype in Bio-Breeding diabetes prone rats. In mice, deletion of functional Gimap5 gene affects the survival and renewal of hematopoietic stem cells in addition to the defects observed in T cells. Here we show that T cells from OTII TCR-transgenic Gimap5sph/sph mice do not proliferate in response to its cognate antigen. Furthermore, T cells from Gimap5 mutant rats and mice show decreased phosphorylation of STAT5 following stimulation with IL-7. Our results suggest that functional Gimap5 is required for optimal signaling through TCR and IL-7R in T cells.