The CLEC-2–podoplanin axis controls fibroblastic reticular cell contractility and lymph node microarchitecture

In lymph nodes, fibroblastic reticular cells (FRCs) form a collagen-based reticular network that supports migratory dendritic cells (DCs) and T cells and transports lymph. A hallmark of FRCs is their propensity to contract collagen, yet this function is poorly understood. Here, we demonstrate that podoplanin (PDPN) regulated actomyosin contractility in FRCs. Under resting conditions, when FRCs are unlikely to encounter mature DCs expressing the PDPN receptor, CLEC-2, PDPN endowed FRCs with contractile function and exerted tension within the reticulum. Upon inflammation, CLEC-2 on mature DCs potently attenuated PDPN-mediated contractility, resulting in FRC relaxation and reduced tissue stiffness. Disrupting PDPN function altered the homeostasis and spacing of FRCs and T cells, resulting in an expanded reticular network and enhanced immunity

Small RNAs and Small Proteins Involved in Resistance to Cell Envelope Stress and Acid Shock in Escherichia coli: Analysis of a Bar-Coded Mutant Collection▿ †

More than 80 small regulatory RNAs (sRNAs) and 60 proteins of 16 to 50 amino acids (small proteins) are encoded in the Escherichia coli genome. The vast majority of the corresponding genes have no known function. We screened 125 DNA bar-coded mutants to identify novel cell envelope stress and acute acid shock phenotypes associated with deletions of genes coding for sRNAs and small proteins. Nine deletion mutants (ssrA, micA, ybaM, ryeF, yqcG, sroH, ybhT, yobF, and glmY) were sensitive to cell envelope stress and two were resistant (rybB and blr). Deletion mutants of genes coding for four small proteins (yqgB, mgrB, yobF, and yceO) were sensitive to acute acid stress. We confirmed each of these phenotypes in one-on-one competition assays against otherwise-wild-type lacZ mutant cells. A more detailed investigation of the SsrA phenotype suggests that ribosome release is critical for resistance to cell envelope stress. The bar-coded deletion collection we generated can be screened for sensitivity or resistance to virtually any stress condition

Lymph node fibroblastic reticular cell transplants show robust therapeutic efficacy in high-mortality murine sepsis

Sepsis is an aggressive inflammatory syndrome and a global health burden estimated to kill 7.3 million people annually. Single-target molecular therapies have not addressed the multiple disease pathways triggered by septic injury. Cell therapies might offer a broader set of mechanisms of action that benefit complex, multifocal disease processes. We describe a population of immune-specialized myofibroblasts derived from lymph node tissue, termed fibroblastic reticular cells (FRCs). Because FRCs have an immunoregulatory function in lymph nodes, we hypothesized that ex vivo–expanded FRCs would control inflammation when administered therapeutically. Indeed, a single injection of ex vivo–expanded allogeneic FRCs reduced mortality in mouse models of sepsis when administered at early or late time points after septic onset. Mice treated with FRCs exhibited lower local and systemic concentrations of proinflammatory cytokines and reduced bacteremia. When administered 4 hours after induction of lipopolysaccharide endotoxemia, or cecal ligation and puncture (CLP) sepsis in mice, FRCs reduced deaths by at least 70%. When administered late in disease (16 hours after CLP), FRCs still conveyed a robust survival advantage (44% survival compared to 0% for controls). FRC therapy was dependent on the metabolic activity of nitric oxide synthase 2 (NOS2) as the primary molecular mechanism of drug action in the mice. Together, these data describe a new anti-inflammatory cell type and provide preclinical evidence for therapeutic efficacy in severe sepsis that warrants further translational study

Podoplanin-rich stromal networks induce dendritic cell motility via activation of the C-type lectin receptor CLEC-2

To initiate adaptive immunity, dendritic cells (DCs) move from parenchymal tissues to lymphoid organs by migrating along stromal scaffolds that display the glycoprotein podoplanin (PDPN). PDPN is expressed by lymphatic endothelial and fibroblastic reticular cells and promotes blood-lymph separation during development by activating the C-type lectin receptor, CLEC-2, on platelets. Here, we describe a role for CLEC-2 in the morphodynamic behavior and motility of DCs. CLEC-2 deficiency in DCs impaired their entry into lymphatics and trafficking to and within lymph nodes, thereby reducing T cell priming. CLEC-2 engagement of PDPN was necessary for DCs to spread and migrate along stromal surfaces and sufficient to induce membrane protrusions. CLEC-2 activation triggered cell spreading via downregulation of RhoA activity and myosin light-chain phosphorylation and triggered F-actin-rich protrusions via Vav signaling and Rac1 activation. Thus, activation of CLEC-2 by PDPN rearranges the actin cytoskeleton in DCs to promote efficient motility along stromal surfaces

TGFβ attenuates tumour response to PD-L1 blockade by contributing to exclusion of T cells

Therapeutic antibodies that block the programmed death-1 (PD-1)-programmed death-ligand 1 (PD-L1) pathway can induce robust and durable responses in patients with various cancers, including metastatic urothelial cancer. However, these responses only occur in a subset of patients. Elucidating the determinants of response and resistance is key to improving outcomes and developing new treatment strategies. Here we examined tumours from a large cohort of patients with metastatic urothelial cancer who were treated with an anti-PD-L1 agent (atezolizumab) and identified major determinants of clinical outcome. Response to treatment was associated with CD8 + T-effector cell phenotype and, to an even greater extent, high neoantigen or tumour mutation burden. Lack of response was associated with a signature of transforming growth factor β (TGFβ) signalling in fibroblasts. This occurred particularly in patients with tumours, which showed exclusion of CD8 + T cells from the tumour parenchyma that were instead found in the fibroblast-and collagen-rich peritumoural stroma; a common phenotype among patients with metastatic urothelial cancer. Using a mouse model that recapitulates this immune-excluded phenotype, we found that therapeutic co-Administration of TGFβ-blocking and anti-PD-L1 antibodies reduced TGFβ signalling in stromal cells, facilitated T-cell penetration into the centre of tumours, and provoked vigorous anti-Tumour immunity and tumour regression. Integration of these three independent biological features provides the best basis for understanding patient outcome in this setting and suggests that TGFβ shapes the tumour microenvironment to restrain anti-Tumour immunity by restricting T-cell infiltration

TGFβ attenuates tumour response to PD-L1 blockade by contributing to exclusion of T cells.

Therapeutic antibodies that block the programmed death-1 (PD-1)-programmed death-ligand 1 (PD-L1) pathway can induce robust and durable responses in patients with various cancers, including metastatic urothelial cancer. However, these responses only occur in a subset of patients. Elucidating the determinants of response and resistance is key to improving outcomes and developing new treatment strategies. Here we examined tumours from a large cohort of patients with metastatic urothelial cancer who were treated with an anti-PD-L1 agent (atezolizumab) and identified major determinants of clinical outcome. Response to treatment was associated with CD8+ T-effector cell phenotype and, to an even greater extent, high neoantigen or tumour mutation burden. Lack of response was associated with a signature of transforming growth factor β (TGFβ) signalling in fibroblasts. This occurred particularly in patients with tumours, which showed exclusion of CD8+ T cells from the tumour parenchyma that were instead found in the fibroblast- and collagen-rich peritumoural stroma; a common phenotype among patients with metastatic urothelial cancer. Using a mouse model that recapitulates this immune-excluded phenotype, we found that therapeutic co-administration of TGFβ-blocking and anti-PD-L1 antibodies reduced TGFβ signalling in stromal cells, facilitated T-cell penetration into the centre of tumours, and provoked vigorous anti-tumour immunity and tumour regression. Integration of these three independent biological features provides the best basis for understanding patient outcome in this setting and suggests that TGFβ shapes the tumour microenvironment to restrain anti-tumour immunity by restricting T-cell infiltration

Dendritic cells control fibroblastic reticular network tension and lymph node expansion

© 2014 Macmillan Publishers Limited. All rights reservedAfter immunogenic challenge, infiltrating and dividing lymphocytes markedly increase lymph node cellularity, leading to organ expansion. Here we report that the physical elasticity of lymph nodes is maintained in part by podoplanin (PDPN) signalling in stromal fibroblastic reticular cells (FRCs) and its modulation by CLEC-2 expressed on dendritic cells. We show in mouse cells that PDPN induces actomyosin contractility in FRCs via activation of RhoA/C and downstream Rho-associated protein kinase (ROCK). Engagement by CLEC-2 causes PDPN clustering and rapidly uncouples PDPN from RhoA/C activation, relaxing the actomyosin cytoskeleton and permitting FRC stretching. Notably, administration of CLEC-2 protein to immunized mice augments lymph node expansion. In contrast, lymph node expansion is significantly constrained in mice selectively lacking CLEC-2 expression in dendritic cells. Thus, the same dendritic cells that initiate immunity by presenting antigens to T lymphocytes also initiate remodelling of lymph nodes by delivering CLEC-2 to FRCs. CLEC-2 modulation of PDPN signalling permits FRC network stretching and allows for the rapid lymph node expansion--driven by lymphocyte influx and proliferation--that is the critical hallmark of adaptive immunity.info:eu-repo/semantics/publishedVersio