Identity of the elusive IgM Fc receptor (FcμR) in humans

Although Fc receptors (FcRs) for switched immunoglobulin (Ig) isotypes have been extensively characterized, FcR for IgM (FcμR) has defied identification. By retroviral expression and functional cloning, we have identified a complementary DNA (cDNA) encoding a bona fide FcμR in human B-lineage cDNA libraries. FcμR is defined as a transmembrane sialoglycoprotein of ∼60 kD, which contains an extracellular Ig-like domain homologous to two other IgM-binding receptors (polymeric Ig receptor and Fcα/μR) but exhibits an exclusive Fcμ-binding specificity. The cytoplasmic tail of FcμR contains conserved Ser and Tyr residues, but none of the Tyr residues match the immunoreceptor tyrosine-based activation, inhibitory, or switch motifs. Unlike other FcRs, the major cell types expressing FcμR are adaptive immune cells, including B and T lymphocytes. After antigen-receptor ligation or phorbol myristate acetate stimulation, FcμR expression was up-regulated on B cells but was down-modulated on T cells, suggesting differential regulation of FcμR expression during B and T cell activation. Although this receptor was initially designated as Fas apoptotic inhibitory molecule 3, or TOSO, our results indicate that FcμR per se has no inhibitory activity in Fas-mediated apoptosis and that such inhibition is only achieved when anti-Fas antibody of an IgM but not IgG isotype is used for inducing apoptosis.

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Abstract P347: γδ T Cells Drive CD4 + And CD8 + T Cell Activation In Hypertension

Hypertension ◽

10.1161/hyp.70.suppl_1.p347 ◽

2017 ◽

Vol 70 (suppl_1) ◽

Author(s):

Antoine Caillon ◽

Pierre Paradis ◽

Ernesto L Schiffrin

Keyword(s):

T Cells ◽

T Cell ◽

T Lymphocytes ◽

Vascular Injury ◽

T Cell Activation ◽

Cell Activation ◽

Γδ T Cells ◽

Ang Ii ◽

Adaptive Immune Cells ◽

Induced Hypertension

Objective: Both innate (monocyte/macrophages) and adaptive immune cells (T lymphocytes) have been shown to play a role in the development of vascular injury in hypertension. Recently, we demonstrated that a small subset of “innate-like” T lymphocytes, expressing the γ/δ T cell receptor (TCR) rather than the αβ TCR, plays a key role in hypertension and vascular injury. We demonstrated an increased number and activation (CD69 + ) of γδ T cells during the development of hypertension caused by angiotensin (Ang) II infusion, and that deficiency in γδ T cells prevented Ang II-induced hypertension, resistance artery endothelial dysfunction and spleen T-cell activation in mice. We hypothesized that γδ T cells mediate activation of other T cells in hypertension. Method and Results: Fourteen to 15-week old male C57BL/6 wild-type (WT) mice were infused with Ang II (490 ng/kg/min, SC) for 3, 7 and 14 days (n=5-7) and spleen T cell profile was determined by flow cytometry. A correlation was demonstrated between the frequency (FREQ) and the number (#) of activated CD69 + γδ T cells and CD4 + CD69 + T cells (FREQ: r=0.41, P <0.05 and #: r=0.58, P <0.001) and CD8 + CD69 + T cells (FREQ: r=0.36, P <0.05 and #: r=0.50, P <0.01). We also demonstrated a high correlation between the # of CD69 + γδ T cells expressing CD27, a marker of interferon-γ expressing cells and a member of the T-T interaction molecules, with CD4 + CD69 + (r=0.88, P <0.001) and CD8 + CD69 + (r=0.81, P <0.01) T cells after 7 days of Ang II infusion. Conclusion: This study demonstrated an association between CD27 + CD69 + γδ T cells and activated T cells. These results suggest that γδ T cells drive activation of other T cells in Ang II-induced hypertension. Targeting γδ T cells may contribute to reduce inflammation in hypertension.

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Signaling function of PRC2 is essential for TCR-driven T cell responses

Journal of Experimental Medicine ◽

10.1084/jem.20170084 ◽

2018 ◽

Vol 215 (4) ◽

pp. 1101-1113 ◽

Cited By ~ 16

Author(s):

Marc-Werner Dobenecker ◽

Joon Seok Park ◽

Jonas Marcello ◽

Michael T. McCabe ◽

Richard Gregory ◽

...

Keyword(s):

T Cells ◽

T Cell ◽

T Cell Activation ◽

Cell Activation ◽

Therapeutic Potential ◽

Cell Types ◽

Polycomb Repressive Complex 2 ◽

Histone Lysine Methyltransferases

Differentiation and activation of T cells require the activity of numerous histone lysine methyltransferases (HMT) that control the transcriptional T cell output. One of the most potent regulators of T cell differentiation is the HMT Ezh2. Ezh2 is a key enzymatic component of polycomb repressive complex 2 (PRC2), which silences gene expression by histone H3 di/tri-methylation at lysine 27. Surprisingly, in many cell types, including T cells, Ezh2 is localized in both the nucleus and the cytosol. Here we show the presence of a nuclear-like PRC2 complex in T cell cytosol and demonstrate a role of cytosolic PRC2 in T cell antigen receptor (TCR)–mediated signaling. We show that short-term suppression of PRC2 precludes TCR-driven T cell activation in vitro. We also demonstrate that pharmacological inhibition of PRC2 in vivo greatly attenuates the severe T cell–driven autoimmunity caused by regulatory T cell depletion. Our data reveal cytoplasmic PRC2 is one of the most potent regulators of T cell activation and point toward the therapeutic potential of PRC2 inhibitors for the treatment of T cell–driven autoimmune diseases.

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Comparative analysis of B7-1 and B7-2 costimulatory ligands: expression and function.

Journal of Experimental Medicine ◽

10.1084/jem.180.2.631 ◽

1994 ◽

Vol 180 (2) ◽

pp. 631-640 ◽

Cited By ~ 468

Author(s):

K S Hathcock ◽

G Laszlo ◽

C Pucillo ◽

P Linsley ◽

R J Hodes

Keyword(s):

T Cell ◽

B Cells ◽

T Cell Activation ◽

Cell Activation ◽

Interleukin 2 ◽

Cell Types ◽

Cell Receptor ◽

Costimulatory Molecules ◽

Tcr Signaling ◽

And Function

Antigen-specific T cell activation requires the engagement of the T cell receptor (TCR) with antigen as well as the engagement of appropriate costimulatory molecules. The most extensively characterized pathway of costimulation has been that involving the interaction of CD28 and CTLA4 on the T cell with B7 (now termed B7-1) on antigen presenting cells. Recently, B7-2 a second costimulatory ligand for CTLA4, was described, demonstrating the potential complexity of costimulatory interactions. This report examines and compares the expression and function of B7-1 and B7-2. Overall these results indicate that (a) B7-1 and B7-2 can be expressed by multiple cell types, including B cells, T cells, macrophages, and dendritic cells, all of which are therefore candidate populations for delivering costimulatory signals mediated by these molecules; (b) stimulating B cells with either LPS or anti-IgD-dextran induced expression of both B7-1 and B7-2, and peak expression of both costimulatory molecules occurred after 18-42 h of culture. Expression of B7-2 on these B cell populations was significantly higher than expression of B7-1 at all times assayed after stimulation; (c) blocking of B7-2 costimulatory activity inhibited TCR-dependent T cell proliferation and cytokine production, without affecting early consequences of TCR signaling such as induction of CD69 or interleukin 2 receptor alpha (IL-2R alpha); and (d) expression of B7-1 and of B7-2 can be regulated by a variety of stimuli. Moreover, expression of B7-1 and B7-2 can be independently regulated by the same stimulus, providing an additional complexity in the mechanisms available for regulating costimulation and hence immune response.

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APOBEC3G: an intracellular centurion

Philosophical Transactions of the Royal Society B Biological Sciences ◽

10.1098/rstb.2008.0193 ◽

2008 ◽

Vol 364 (1517) ◽

pp. 689-703 ◽

Cited By ~ 33

Author(s):

Ya-Lin Chiu ◽

Warner C Greene

Keyword(s):

T Cells ◽

Molecular Mass ◽

T Cell Activation ◽

Cd4 T Cells ◽

Cell Activation ◽

Protein Complexes ◽

Biological Activities ◽

Cell Types ◽

Highly Active ◽

Hiv 1

The intrinsic antiretroviral factor APOBEC3G (A3G) is highly active against HIV-1 and other retroviruses. In different cell types, A3G is expressed in high-molecular-mass (HMM) RNA–protein complexes or low-molecular-mass (LMM) forms displaying different biological activities. In resting CD4 T cells, a LMM form of A3G potently restricts HIV-1 infection soon after virion entry. However, when T cells are activated, LMM A3G is recruited into HMM complexes that include Staufen-containing RNA granules. These complexes are probably nucleated by the induced expression of Alu/hY retroelement RNAs that accompany T-cell activation. HMM A3G sequesters these retroelement RNAs away from the nuclear long interspersed nuclear element-derived enzymes required for Alu/hY retrotransposition. Human immunodeficiency virus (HIV) exploits this ‘window of opportunity’ provided by the loss of LMM A3G in activated CD4 T cells to productively infect these cells. During HIV virion formation, newly synthesized LMM A3G is preferentially encapsidated but only under conditions where Vif is absent and thus not able to target A3G for proteasome-mediated degradation. Together, these findings highlight the discrete functions of the different forms of A3G. LMM A3G opposes the external threat posed by exogenous retroviruses, while HMM A3G complexes oppose the internal threat posed by the retrotransposition of select types of retroelements.

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Critical role for perforin and Fas-dependent killing of dendritic cells in the control of inflammation

Blood ◽

10.1182/blood-2011-06-363994 ◽

2012 ◽

Vol 119 (1) ◽

pp. 127-136 ◽

Cited By ~ 42

Author(s):

Min Chen ◽

Kumar Felix ◽

Jin Wang

Keyword(s):

T Cells ◽

T Cell ◽

T Cell Activation ◽

Cd8 T Cells ◽

Cell Activation ◽

Inflammatory Responses ◽

Critical Role ◽

Cell Types ◽

Activated T Cells ◽

Ifn Γ

AbstractAfter stimulation of antigen-specific T cells, dendritic cell (DCs) are susceptible to killing by these activated T cells that involve perforin and Fas-dependent mechanisms. Fas-dependent DC apoptosis has been shown to limit DC accumulation and prevent the development of autoimmunity. However, a role for perforin in the maintenance of DC homeostasis for immune regulation remains to be determined. Here we show that perforin deficiency in mice, together with the deletion of Fas in DCs (perforin−/−DC-Fas−/−), led to DC accumulation, uncontrolled T-cell activation, and IFN-γ production by CD8+ T cells, resulting in the development of lethal hemophagocytic lymphohistiocytosis. Consistently, adoptive transfer of Fas−/− DCs induced over-activation and IFN-γ production in perforin−/− CD8+ T cells. Neutralization of IFN-γ prevented the spreading of inflammatory responses to different cell types and protected the survival of perforin−/−DC-Fas−/− mice. Our data suggest that perforin and Fas synergize in the maintenance of DC homeostasis to limit T cell activation, and prevent the initiation of an inflammatory cascade.

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Expression of the Receptor Tyrosine Kinase EphB2 on Dendritic Cells Is Modulated by Toll-Like Receptor Ligation but Is Not Required for T Cell Activation

PLoS ONE ◽

10.1371/journal.pone.0138835 ◽

2015 ◽

Vol 10 (9) ◽

pp. e0138835 ◽

Cited By ~ 4

Author(s):

Patrice N. Mimche ◽

Lauren M. Brady ◽

Shirley Keeton ◽

David S. J. Fenne ◽

Thayer P. King ◽

...

Keyword(s):

Dendritic Cells ◽

T Cell ◽

Tyrosine Kinase ◽

T Cell Activation ◽

Receptor Tyrosine Kinase ◽

Cell Activation ◽

Toll Like Receptor ◽

Receptor Ligation

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Reclassification of classic T cell subsets and identification of novel cell types by single-cell RNA sequencing

10.21203/rs.3.rs-79282/v1 ◽

2020 ◽

Author(s):

Xiangru Shen ◽

Xuefei Wang ◽

Shan Chen ◽

Hongyi Liu ◽

Ni Hong ◽

...

Keyword(s):

T Cell ◽

Single Cell ◽

Rna Sequencing ◽

T Cell Activation ◽

Cell Activation ◽

Expression Profiles ◽

Gene Expression Profiles ◽

Cell Types ◽

T Cell Subsets ◽

Single Cell Rna Sequencing

Abstract Single cell RNA sequencing (scRNA-seq) clusters cells using genome-wide gene expression profiles. The relationship between scRNA-seq Clustered-Populations (scCPops) and cell surface marker-defined classic T cell subsets is unclear. Here, we interrogated 6 bead-enriched T cell subsets with 62,235 single cell transcriptomes and re-grouped them into 9 scCPops. Bead-enriched CD4 Naïve, CD8 Naïve and CD4 memory were mainly clustered into their scCPop counterparts, while the other T cell subsets were clustered into multiple scCPops including unexpected mucosal-associated invariant T cell and natural killer T cell. Most interestingly, we discovered a new T cell type that highly expressed Interferon Signaling Associated Genes (ISAGs), namely IFNhi T. We further enriched IFNhi T for scRNA-seq analyses. IFNhi T cluster disappeared on tSNE after removing ISAGs, and IFNhi T cluster showed up by tSNE analyses of ISAGs alone, indicating ISAGs are the major contributor of IFNhi T cluster. BST2+ cells and BST2- cells showing different efficiencies of T cell activation indicates high ISAGs may contribute to quick immune responses.

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Shortening of 3' UTRs in most cell types composing tumor tissues implicates alternative polyadenylation in protein metabolism

10.1101/2021.06.30.450496 ◽

2021 ◽

Author(s):

Dominik Burri ◽

Mihaela Zavolan

Keyword(s):

T Cell Activation ◽

Cell Activation ◽

Alternative Polyadenylation ◽

Cell Types ◽

Regulatory Elements ◽

Computational Method ◽

Control Tissue ◽

Mrna Maturation ◽

The Individual ◽

And Control

During pre-mRNA maturation 3' end processing can occur at different polyadenylation sites in the 3' untranslated region (3' UTR) to give rise to transcript isoforms that differ in the length of their 3' UTRs. Longer 3' UTRs contain additional cis-regulatory elements that impact the fate of the transcript and/or of the resulting protein. Extensive alternative polyadenylation (APA) has been observed in cancers, but the mechanisms and roles remain elusive. In particular, it is unclear whether the APA occurs in the malignant cells or in other cell types that infiltrate the tumor. To resolve this, we developed a computational method, called SCUREL, that quantifies changes in 3' UTR length between groups of cells, including cells of the same type originating from tumor and control tissue. We used this method to study APA in human lung adenocarcinoma (LUAD). SCUREL relies solely on annotated 3' UTRs and on control systems, such as T cell activation and spermatogenesis gives qualitatively similar results at much greater sensitivity compared to the previously published scAPA method. In the LUAD samples, we find a general trend towards 3' UTR shortening not only in cancer cells compared to the cell type of origin, but also when comparing other cell types from the tumor vs. the control tissue environment. However, we also find high variability in the individual targets between patients. The findings help to understand the extent and impact of APA in LUAD, which may support improvements in diagnosis and treatment.

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Lymphatic Control of the Tumor Immune Microenvironment

Blood ◽

10.1182/blood-2019-123389 ◽

2019 ◽

Vol 134 (Supplement_1) ◽

pp. SCI-46-SCI-46

Author(s):

Melody A. Swartz

Keyword(s):

T Cell ◽

Tumor Microenvironment ◽

Tumor Cell ◽

Cancer Immunotherapy ◽

T Cell Activation ◽

Immune Suppression ◽

Cell Activation ◽

Conflicts Of Interest ◽

Lymphatic Vessels ◽

Cell Types

Tumor engagement or activation of surrounding lymphatic vessels is well-known to correlate with tumor progression and metastasis in melanoma and many other cancers. We and others have identified several mechanisms by which the lymphatic growth factor VEGF-C and lymphangiogenesis can promote metastasis, including (i) increasing immune suppressive cell types and factors in the tumor microenvironment both directly and indirectly, (ii) inhibiting maturation of antigen-presenting cells and T cell activation, and (iii) driving changes in the stromal microenvironment that promote both cancer invasion and immune suppression. However, lymphatic activation also enhances communication with cells in the draining lymph node by antigen and cell transport, which may trigger the initiation of adaptive immune responses against the tumor. Under normal conditions, the potential anti-tumor effects are rendered 'dormant' by the pro-tumor immune suppression, and the tumor progresses. However, we are now observing that lymphangiogenic tumors are exceptionally responsive to immunotherapy, implying that the anti-tumor aspects can be unleashed when the overall balance of pro- and anti-tumor immune aspects is tipped enough towards the latter (e.g., upon tumor cell killing). On the mechanistic side, we are finding that 'lymphangiogenic potentiation' depends on tumor cell infiltration of both CD103+ dendritic cells and naïve T cells, driving local T cell education post-immunotherapy and antigen spreading. On the translational side, we are developing novel strategies to exploit lymphangiogenesis for cancer immunotherapy. Understanding the yin and yang of lymphatic activation in the tumor microenvironment and how it affects immunity may lead to exciting new translational strategies for cancer immunotherapy. Disclosures No relevant conflicts of interest to declare.

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