Fibroblasts: The B's knees of follicular lymphoma.

Fibroblasts are the immunological architects of lymph nodes. In this issue of Immunity, Mourcin et al. describe the human tonsil fibroblast landscape and predicted T and B cell interactions. Transcriptomic changes in follicular lymphoma could provide untapped clinical targets.

A bird's eye view of fibroblast heterogeneity: A pan-disease, pan-cancer perspective.

Fibroblasts, custodians of tissue architecture and function, are no longer considered a monolithic entity across tissues and disease indications. Recent advances in single-cell technologies provide an unrestricted, high-resolution view of fibroblast heterogeneity that exists within and across tissues. In this review, we summarize a compendium of single-cell transcriptomic studies and provide a comprehensive accounting of fibroblast subsets, many of which have been described to occupy specific niches in tissues at homeostatic and pathologic states. Understanding this heterogeneity is particularly important in the context of cancer, as the diverse cancer-associated fibroblast (CAF) phenotypes in the tumor microenvironment (TME) are directly impacted by the expression phenotypes of their predecessors. Relationships between these heterogeneous populations often accompany and influence response to therapy in cancer and fibrosis. We further highlight the importance of integrating single-cell studies to deduce common fibroblast phenotypes across disease states, which will facilitate the identification of common signaling pathways, gene regulatory programs, and cell surface markers that are going to advance drug discovery and targeting.

Fibroblastic reticular cells provide a supportive niche for lymph node-resident macrophages.

The lymph node (LN) is home to resident macrophage populations that are essential for immune function and homeostasis, but key factors controlling this niche are undefined. Here, we show that fibroblastic reticular cells (FRCs) are an essential component of the LN macrophage niche. Genetic ablation of FRCs caused rapid loss of macrophages and monocytes from LNs across two in vivo models. Macrophages co-localized with FRCs in human LNs, and murine single-cell RNA-sequencing revealed that FRC subsets broadly expressed master macrophage regulator CSF1. Functional assays containing purified FRCs and monocytes showed that CSF1R signaling was sufficient to support macrophage development. These effects were conserved between mouse and human systems. These data indicate an important role for FRCs in maintaining the LN parenchymal macrophage niche.

Transcriptional profiling of stroma from inflamed and resting lymph nodes defines immunological hallmarks.

Lymph node stromal cells (LNSCs) closely regulate immunity and self-tolerance, yet key aspects of their biology remain poorly elucidated. Here, comparative transcriptomic analyses of mouse LNSC subsets demonstrated the expression of important immune mediators, growth factors and previously unknown structural components. Pairwise analyses of ligands and cognate receptors across hematopoietic and stromal subsets suggested a complex web of crosstalk. Fibroblastic reticular cells (FRCs) showed enrichment for higher expression of genes relevant to cytokine signaling, relative to their expression in skin and thymic fibroblasts. LNSCs from inflamed lymph nodes upregulated expression of genes encoding chemokines and molecules involved in the acute-phase response and the antigen-processing and antigen-presentation machinery. Poorly studied podoplanin (gp38)-negative CD31(-) LNSCs showed similarities to FRCs but lacked expression of interleukin 7 (IL-7) and were identified as myofibroblastic pericytes that expressed integrin α(7). Together our data comprehensively describe the transcriptional characteristics of LNSC subsets.

Autonomy-supportive parenting as a moderator of associations between ethnic and racial identity processes and psychological adjustment during college.

OBJECTIVES: The purpose of this study was to test the roles of ethnic and racial identity (ERI) processes and autonomy-supportive parenting on college students' psychological adjustment. METHOD: American college students of color (N = 505) completed questionnaires assessing ERI exploration and commitment, autonomy-supportive parenting, and psychological adjustment (self-esteem, depressive symptoms). Key variables were operationalized as latent constructs, and main and interaction effects were tested using the latent moderated structural equation modeling approach. RESULTS: Higher levels of ERI commitment (but not exploration) and parental autonomy support each uniquely predicted higher levels of self-esteem and lower levels of depressive symptoms. Parental autonomy support moderated associations between ERI processes and psychological adjustment, and the nature of moderation did not differ across Black and Latino/a/x students. CONCLUSIONS: Supporting the psychological adjustment of college students of color necessitates acknowledging the importance of both parental and institutional efforts to encourage students' autonomy strivings and ERI processes. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Regulated release of nitric oxide by nonhematopoietic stroma controls expansion of the activated T cell pool in lymph nodes.

Fibroblastic reticular cells (FRCs) and lymphatic endothelial cells (LECs) are nonhematopoietic stromal cells of lymphoid organs. They influence the migration and homeostasis of naive T cells; however, their influence on activated T cells remains undescribed. Here we report that FRCs and LECs inhibited T cell proliferation through a tightly regulated mechanism dependent on nitric oxide synthase 2 (NOS2). Expression of NOS2 and production of nitric oxide paralleled the activation of T cells and required a tripartite synergism of interferon-γ, tumor necrosis factor and direct contact with activated T cells. Notably, in vivo expression of NOS2 by FRCs and LECs regulated the size of the activated T cell pool. Our study elucidates an as-yet-unrecognized role for the lymph node stromal niche in controlling T cell responses.

Cancer-Associated Fibroblasts and T Cells: From Mechanisms to Outcomes.

Over the past decade, T cell immunotherapy has changed the face of cancer treatment, providing robust treatment options for several previously intractable cancers. Unfortunately, many epithelial tumors with high mortality rates respond poorly to immunotherapy, and an understanding of the key impediments is urgently required. Cancer-associated fibroblasts (CAFs) comprise the most frequent nonneoplastic cellular component in most solid tumors. Far from an inert scaffold, CAFs significantly influence tumor neogenesis, persistence, and metastasis and are emerging as a key player in immunotherapy resistance. In this review, we discuss the physical and chemical barriers that CAFs place between effector T cells and their tumor cell targets, and the therapies poised to target them.

Financial, resource, and psychological impacts of COVID-19 on U.S. College students: Who is impacted and what are the implications for adjustment and well-being?

The COVID-19 pandemic has been highly disruptive for college students and has altered their living, learning, and working environments. COVID-19-related financial impact, access to needed resources, and psychological impacts are reported amongst college students, though research has yet to examine how severity and type of impact varies by student. This study investigated how undergraduate college students were impacted during the COVID-19 pandemic regarding finances, access to needed resources, and psychological well-being, and explored outcomes associated with patterns of perceived impact. Participants were 894 college students at a southeastern university who completed an online survey during the Spring 2021 semester. Students reported on how the COVID-19 pandemic affected their finances, resources, and psychological health; students also reported their current self-esteem, and adjustment to college (academic and relational). Latent profile analysis was utilized to develop profiles of COVID-19-related impact. Results indicated that most participants experienced moderate levels of financial and psychological impact but low resource impact (34.6%) or experienced low impact across the range of financial, resource, and psychological domains (32.5%). Seventeen percent were highly impacted across all domains and 15.8% experienced moderate financial and resource impact but low psychological impact. Student gender identity, generational status, and first-year status were significant predictors of profile membership - student race was not associated with profile membership. Highly impacted students had significantly lower self-esteem and college adjustment compared to students in relatively less-impacted profiles.

Parental Self-Efficacy and Physiological Responses to Stress among Mothers of Early Adolescents.

Little research addresses how parental self-efficacy is related to stress responses, and no research does so among parents of early adolescents. To fill this research gap, the current study examined the association between maternal self-efficacy and physiological stress responses during early adolescence. Participants were 68 mother-early adolescent dyads with youth in the 6th grade (M = 11 years; 56% female). Physiological responses (i.e., skin conductance, respiratory sinus arrythmia, cortisol) were measured before and after mothers observed their children engage in a modified Trier Social Stress Test for Children. Mothers reported on parental self-efficacy. Mothers with higher parental self-efficacy exhibited a more moderate skin conductance response to the speech portion of the task, and a smaller increase in cortisol, compared to mothers with lower parental self-efficacy. Respiratory sinus arrhythmia change was not related to parental self-efficacy. The findings are consistent with a "caring but confident" physiological profile among mothers with high parental self-efficacy, suggesting that greater confidence about parental influence might reduce parents' experience of stress/anxiety as they observe children face certain challenges.

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.

The human lymph node microenvironment unilaterally regulates T-cell activation and differentiation.

The microenvironment of lymphoid organs can aid healthy immune function through provision of both structural and molecular support. In mice, fibroblastic reticular cells (FRCs) create an essential T-cell support structure within lymph nodes, while human FRCs are largely unstudied. Here, we show that FRCs create a regulatory checkpoint in human peripheral T-cell activation through 4 mechanisms simultaneously utilised. Human tonsil and lymph node-derived FRCs constrained the proliferation of both naïve and pre-activated T cells, skewing their differentiation away from a central memory T-cell phenotype. FRCs acted unilaterally without requiring T-cell feedback, imposing suppression via indoleamine-2,3-dioxygenase, adenosine 2A Receptor, prostaglandin E2, and transforming growth factor beta receptor (TGFßR). Each mechanistic pathway was druggable, and a cocktail of inhibitors, targeting all 4 mechanisms, entirely reversed the suppressive effect of FRCs. T cells were not permanently anergised by FRCs, and studies using chimeric antigen receptor (CAR) T cells showed that immunotherapeutic T cells retained effector functions in the presence of FRCs. Since mice were not suitable as a proof-of-concept model, we instead developed a novel human tissue-based in situ assay. Human T cells stimulated using standard methods within fresh tonsil slices did not proliferate except in the presence of inhibitors described above. Collectively, we define a 4-part molecular mechanism by which FRCs regulate the T-cell response to strongly activating events in secondary lymphoid organs while permitting activated and CAR T cells to utilise effector functions. Our results define 4 feasible strategies, used alone or in combinations, to boost primary T-cell responses to infection or cancer by pharmacologically targeting FRCs.

In Vitro Suppression of T Cell Proliferation Is a Conserved Function of Primary and Immortalized Human Cancer-Associated Fibroblasts.

T cell immunotherapy is now a mainstay therapy for several blood-borne cancers as well as metastatic melanoma. Unfortunately, many epithelial tumors respond poorly to immunotherapy, and the reasons for this are not well understood. Cancer-associated fibroblasts (CAFs) are the most frequent non-neoplastic cell type in most solid tumors, and they are emerging as a key player in immunotherapy resistance. A range of immortalized CAF lines will be essential tools that will allow us to understand immune responses against cancer and develop novel strategies for cancer immunotherapy. To study the effect of CAFs on T cell proliferation, we created and characterized a number of novel immortalized human CAFs lines (Im-CAFs) from human breast, colon, and pancreatic carcinomas. Im-CAFs shared similar phenotypes, matrix remodeling and contraction capabilities, and growth and migration rates compared to the primary CAFs. Using primary isolates from breast carcinoma, colorectal carcinoma, and pancreatic ductal adenocarcinoma, we report that CAFs across major tumor types are able to potently suppress T cell proliferation in vitro. Im-CAFs retained this property. Im-CAFs are a key tool that will provide important insights into the mechanisms of CAF-mediated T cell suppression through techniques such as CRISPR-Cas9 modification, molecular screens, and pipeline drug testing.

Youth Parasympathetic Functioning Moderates Relations between Cumulative Family Risk and Internalizing Behaviors.

Problematic family functioning places young adolescents at risk for internalizing behaviors. However, not all adolescents who experience family risk develop internalizing behaviors during early adolescence. Informed by a cumulative risk perspective, the current study examined whether associations between cumulative family risk, as well as particular family risk domains, and youth internalizing behaviors are moderated by youth parasympathetic reactivity. Participants include 68 young adolescents in 6th grade. Youth were 56% female, 41% African American, and 54% European American. For young adolescents who experienced higher change in respiratory sinus arrhythmia during a challenge/stressor task, greater cumulative family risk, exposure to more family risk domains, and several particular risk factors (maternal psychological well-being, marital/family system risk), were associated with higher levels of internalizing behaviors. The findings from this study demonstrate that the extent to which both particular family risk factors and cumulative family risk place youth at increased risk for internalizing behaviors depends on youth's parasympathetic functioning.

Intronic miR-211 assumes the tumor suppressive function of its host gene in melanoma.

When it escapes early detection, malignant melanoma becomes a highly lethal and treatment-refractory cancer. Melastatin is greatly downregulated in metastatic melanomas and is widely believed to function as a melanoma tumor suppressor. Here we report that tumor suppressive activity is not mediated by melastatin but instead by a microRNA (miR-211) hosted within an intron of melastatin. Increasing expression of miR-211 but not melastatin reduced migration and invasion of malignant and highly invasive human melanomas characterized by low levels of melastatin and miR-211. An unbiased network analysis of melanoma-expressed genes filtered for their roles in metastasis identified three central node genes: IGF2R, TGFBR2, and NFAT5. Expression of these genes was reduced by miR-211, and knockdown of each gene phenocopied the effects of increased miR-211 on melanoma invasiveness. These data implicate miR-211 as a suppressor of melanoma invasion whose expression is silenced or selected against via suppression of the entire melastatin locus during human melanoma progression.

Leukocyte-Stromal Interactions Within Lymph Nodes.

Lymph nodes play a crucial role in the formation and initiation of immune responses, allowing lymphocytes to efficiently scan for foreign antigens and serving as rendezvous points for leukocyte-antigen interactions. Here we describe the major stromal subsets found in lymph nodes, including fibroblastic reticular cells, lymphatic endothelial cells, blood endothelial cells, marginal reticular cells, follicular dendritic cells and other poorly defined subsets such as integrin alpha-7+ pericytes. We focus on biomedically relevant interactions with T cells, B cells and dendritic cells, describing pro-survival mechanisms of support for these cells, promotion of their migration and tolerance-inducing mechanisms that help keep the body free of autoimmune-mediated damage.

Stromal and hematopoietic cells in secondary lymphoid organs: partners in immunity.

Secondary lymphoid organs (SLOs), including lymph nodes, Peyer's patches, and the spleen, have evolved to bring cells of the immune system together. In these collaborative environments, lymphocytes scan the surfaces of antigen-presenting cells for cognate antigens, while moving along stromal networks. The cell-cell interactions between stromal and hematopoietic cells in SLOs are therefore integral to the normal functioning of these tissues. Not only do stromal cells physically construct SLO architecture but they are essential for regulating hematopoietic populations within these domains. Stromal cells interact closely with lymphocytes and dendritic cells, providing scaffolds on which these cells migrate, and recruiting them into niches by secreting chemokines. Within lymph nodes, stromal cell-ensheathed conduit networks transport small antigens deep into the SLO parenchyma. More recently, stromal cells have been found to induce peripheral CD8(+) T-cell tolerance and control the extent to which newly activated T cells proliferate within lymph nodes. Thus, stromal-hematopoietic crosstalk has important consequences for regulating immune cell function within SLOs. In addition, stromal cell interactions with hematopoietic cells, other stroma, and the inflammatory milieu have profound effects on key stromal functions. Here, we examine ways in which these interactions within the lymph node environment influence the adaptive immune response.

Enriched protein screening of human bone marrow mesenchymal stromal cell secretions reveals MFAP5 and PENK as novel IL-10 modulators.

The secreted proteins from a cell constitute a natural biologic library that can offer significant insight into human health and disease. Discovering new secreted proteins from cells is bounded by the limitations of traditional separation and detection tools to physically fractionate and analyze samples. Here, we present a new method to systematically identify bioactive cell-secreted proteins that circumvent traditional proteomic methods by first enriching for protein candidates by differential gene expression profiling. The bone marrow stromal cell secretome was analyzed using enriched gene expression datasets in combination with potency assay testing. Four proteins expressed by stromal cells with previously unknown anti-inflammatory properties were identified, two of which provided a significant survival benefit to mice challenged with lethal endotoxic shock. Greater than 85% of secreted factors were recaptured that were otherwise undetected by proteomic methods, and remarkable hit rates of 18% in vitro and 9% in vivo were achieved.

Tetraspanin TSPAN12 regulates tumor growth and metastasis and inhibits ß-catenin degradation.

Ablation of tetraspanin protein TSPAN12 from human MDA-MB-231 cells significantly decreased primary tumor xenograft growth, while increasing tumor apoptosis. Furthermore, TSPAN12 removal markedly enhanced tumor-endothelial interactions and increased metastasis to mouse lungs. TSPAN12 removal from human MDA-MB-231 cells also caused diminished association between FZD4 (a key canonical Wnt pathway receptor) and its co-receptor LRP5. The result likely explains substantially enhanced proteosomal degradation of ß-catenin, a key effecter of canonical Wnt signaling. Consistent with disrupted canonical Wnt signaling, TSPAN12 ablation altered expression of LRP5, Naked 1 and 2, DVL2, DVL3, Axin 1, and GSKß3 proteins. TSPAN12 ablation also altered expression of several genes regulated by ß-catenin (e.g. CCNA1, CCNE2, WISP1, ID4, SFN, ME1) that may help to explain altered tumor growth and metastasis. In conclusion, these results provide the first evidence for TSPAN12 playing a role in supporting primary tumor growth and suppressing metastasis. TSPAN12 appears to function by stabilizing FZD4-LRP5 association, in support of canonical Wnt-pathway signaling, leading to enhanced ß-catenin expression and function.