Gradients of the signaling lipid S1P in lymph nodes position natural killer cells and regulate their interferon-γ response.

The lymph node periphery is an important site for many immunological functions, from pathogen containment to the differentiation of helper T cells, yet the cues that position cells in this region are largely undefined. Here, through the use of a reporter for the signaling lipid S1P (sphingosine 1-phosphate), we found that cells sensed higher concentrations of S1P in the medullary cords than in the T cell zone and that the S1P transporter SPNS2 on lymphatic endothelial cells generated this gradient. Natural killer (NK) cells are located at the periphery of the lymph node, predominantly in the medulla, and we found that expression of SPNS2, expression of the S1P receptor S1PR5 on NK cells, and expression of the chemokine receptor CXCR4 were all required for NK cell localization during homeostasis and rapid production of interferon-γ by NK cells after challenge. Our findings elucidate the spatial cues for NK cell organization and reveal a previously unknown role for S1P in positioning cells within the medulla.

A map of the distribution of sphingosine 1-phosphate in the spleen.

Despite the importance of signaling lipids, many questions remain about their function because few tools are available for charting lipid gradients in vivo. Here we generated a sphingosine 1-phosphate (S1P) reporter mouse and used this mouse to define the distribution of S1P in the spleen. Unexpectedly, the presence of blood did not serve as a predictor of the concentration of signaling-available S1P. Large areas of the red pulp had low concentrations of S1P, while S1P was sensed by cells inside the white pulp near the marginal sinus. The lipid phosphate phosphatase LPP3 maintained low S1P concentrations in the spleen and enabled efficient shuttling of marginal zone B cells. The exquisitely tight regulation of S1P availability might explain how a single lipid can simultaneously orchestrate the movements of many cells of the immune system.

Lymphatic endothelial S1P promotes mitochondrial function and survival in naive T cells.

Effective adaptive immune responses require a large repertoire of naive T cells that migrate throughout the body, rapidly identifying almost any foreign peptide. Because the production of T cells declines with age, naive T cells must be long-lived. However, it remains unclear how naive T cells survive for years while constantly travelling. The chemoattractant sphingosine 1-phosphate (S1P) guides T cell circulation among secondary lymphoid organs, including spleen, lymph nodes and Peyer's patches, where T cells search for antigens. The concentration of S1P is higher in circulatory fluids than in lymphoid organs, and the S1P1 receptor (S1P1R) directs the exit of T cells from the spleen into blood, and from lymph nodes and Peyer's patches into lymph. Here we show that S1P is essential not only for the circulation of naive T cells, but also for their survival. Using transgenic mouse models, we demonstrate that lymphatic endothelial cells support the survival of T cells by secreting S1P via the transporter SPNS2, that this S1P signals through S1P1R on T cells, and that the requirement for S1P1R is independent of the established role of the receptor in guiding exit from lymph nodes. S1P signalling maintains the mitochondrial content of naive T cells, providing cells with the energy to continue their constant migration. The S1P signalling pathway is being targeted therapeutically to inhibit autoreactive T cell trafficking, and these findings suggest that it may be possible simultaneously to target autoreactive or malignant cell survival.

Exit Strategies: S1P Signaling and T Cell Migration.

Whereas the role of sphingosine 1-phosphate receptor 1 (S1PR1) in T cell egress and the regulation of S1P gradients between lymphoid organs and circulatory fluids in homeostasis are increasingly well understood, much remains to be learned about S1P signaling and distribution during an immune response. Recent data suggest that the role of S1PR1 in directing cells from tissues into circulatory fluids is reprised again and again, particularly in guiding activated T cells from non-lymphoid tissues into lymphatics. Conversely, S1P receptor 2 (S1PR2), which antagonizes migration towards chemokines, confines cells within tissues. Here we review the current understanding of the roles of S1P signaling in activated T cell migration. In this context, we outline open questions, particularly regarding the shape of S1P gradients in different tissues in homeostasis and inflammation, and discuss recent strategies to measure S1P.

Constitutive Lck Activity Drives Sensitivity Differences between CD8+ Memory T Cell Subsets.

CD8(+) T cells develop increased sensitivity following Ag experience, and differences in sensitivity exist between T cell memory subsets. How differential TCR signaling between memory subsets contributes to sensitivity differences is unclear. We show in mouse effector memory T cells (TEM) that >50% of lymphocyte-specific protein tyrosine kinase (Lck) exists in a constitutively active conformation, compared with <20% in central memory T cells (TCM). Immediately proximal to Lck signaling, we observed enhanced Zap-70 phosphorylation in TEM following TCR ligation compared with TCM Furthermore, we observed superior cytotoxic effector function in TEM compared with TCM, and we provide evidence that this results from a lower probability of TCM reaching threshold signaling owing to the decreased magnitude of TCR-proximal signaling. We provide evidence that the differences in Lck constitutive activity between CD8(+) TCM and TEM are due to differential regulation by SH2 domain-containing phosphatase-1 (Shp-1) and C-terminal Src kinase, and we use modeling of early TCR signaling to reveal the significance of these differences. We show that inhibition of Shp-1 results in increased constitutive Lck activity in TCM to levels similar to TEM, as well as increased cytotoxic effector function in TCM Collectively, this work demonstrates a role for constitutive Lck activity in controlling Ag sensitivity, and it suggests that differential activities of TCR-proximal signaling components may contribute to establishing the divergent effector properties of TCM and TEM. This work also identifies Shp-1 as a potential target to improve the cytotoxic effector functions of TCM for adoptive cell therapy applications.

Implementing an Organized Colorectal Cancer Screening Program: Lessons Learned From an Academic-Community Practice.

Introduction: The effectiveness of mailed fecal immunochemical test outreach might be enhanced through an organized colorectal cancer screening program, yet published real-world experiences are limited. We synthesized the process of implementing a colorectal cancer screening program that used mailed fecal immunochemical test outreach in a large integrated academic-community practice. Methods: Data from a pilot mailed fecal immunochemical test program were shared with healthcare system leadership, which inspired the creation of a cross-institutional organized colorectal cancer screening program. In partnership with a centralized population health team and primary care, we defined (1) the institutional approach to colorectal cancer screening, (2) the target population and method for screening, (3) the team responsible for implementation, (4) the healthcare team responsible for decisions and care, (5) a quality assurance structure, and (6) a method for identifying cancer occurrence. Results: The Fred Hutch/UW Medicine Population Health Colorectal Cancer Screening Program began in September 2021. The workflow for mailed fecal immunochemical test outreach included a mailed postcard, a MyChart message from the patient's primary care provider, a fecal immunochemical test kit with a letter signed by the primary care provider and program director, and up to 3 biweekly reminders. Patients without a colonoscopy 3 months after an abnormal fecal immunochemical test result received navigation through the program. In the first program year, we identified 9,719 patients eligible for outreach, and in an intention-to-treat analysis, 32% of patients completed colorectal cancer screening by fecal immunochemical test or colonoscopy. Conclusions: Real-world experiences detailing how to implement organized colorectal cancer screening programs might increase adoption. In our experience, broadly disseminating pilot data, early institutional support, robust data management, and strong cross-departmental relationships were critical to successfully implementing a colorectal cancer screening program that benefits all patients.

Leveraging human-centered design and causal pathway diagramming toward enhanced specification and development of innovative implementation strategies: a case example of an outreach tool to address racial inequities in breast cancer screening.

BACKGROUND: Implementation strategies are strategies to improve uptake of evidence-based practices or interventions and are essential to implementation science. Developing or tailoring implementation strategies may benefit from integrating approaches from other disciplines; yet current guidance on how to effectively incorporate methods from other disciplines to develop and refine innovative implementation strategies is limited. We describe an approach that combines community-engaged methods, human-centered design (HCD) methods, and causal pathway diagramming (CPD)-an implementation science tool to map an implementation strategy as it is intended to work-to develop innovative implementation strategies. METHODS: We use a case example of developing a conversational agent or chatbot to address racial inequities in breast cancer screening via mammography. With an interdisciplinary team including community members and operational leaders, we conducted a rapid evidence review and elicited qualitative data through interviews and focus groups using HCD methods to identify and prioritize key determinants (facilitators and barriers) of the evidence-based intervention (breast cancer screening) and the implementation strategy (chatbot). We developed a CPD using key determinants and proposed strategy mechanisms and proximal outcomes based in conceptual frameworks. RESULTS: We identified key determinants for breast cancer screening and for the chatbot implementation strategy. Mistrust was a key barrier to both completing breast cancer screening and using the chatbot. We focused design for the initial chatbot interaction to engender trust and developed a CPD to guide chatbot development. We used the persuasive health message framework and conceptual frameworks about trust from marketing and artificial intelligence disciplines. We developed a CPD for the initial interaction with the chatbot with engagement as a mechanism to use and trust as a proximal outcome leading to further engagement with the chatbot. CONCLUSIONS: The use of interdisciplinary methods is core to implementation science. HCD is a particularly synergistic discipline with multiple existing applications of HCD to implementation research. We present an extension of this work and an example of the potential value in an integrated community-engaged approach of HCD and implementation science researchers and methods to combine strengths of both disciplines and develop human-centered implementation strategies rooted in causal perspective and healthcare equity.

SPNS2 enables T cell egress from lymph nodes during an immune response.

T cell expression of sphingosine 1-phosphate (S1P) receptor 1 (S1PR1) enables T cell exit from lymph nodes (LNs) into lymph, while endothelial S1PR1 expression regulates vascular permeability. Drugs targeting S1PR1 treat autoimmune disease by trapping pathogenic T cells within LNs, but they have adverse cardiovascular side effects. In homeostasis, the transporter SPNS2 supplies lymph S1P and enables T cell exit, while the transporter MFSD2B supplies most blood S1P and supports vascular function. It is unknown whether SPNS2 remains necessary to supply lymph S1P during an immune response, or whether in inflammation other compensatory transporters are upregulated. Here, using a model of dermal inflammation, we demonstrate that SPNS2 supplies the S1P that guides T cells out of LNs with an ongoing immune response. Furthermore, deletion of Spns2 is protective in a mouse model of multiple sclerosis. These results support the therapeutic potential of SPNS2 inhibitors to achieve spatially specific modulation of S1P signaling.

Redundant cytokine requirement for intestinal microbiota-induced Th17 cell differentiation in draining lymph nodes.

Differentiation of intestinal T helper 17 (Th17) cells, which contribute to mucosal barrier protection from invasive pathogens, is dependent on colonization with distinct commensal bacteria. Segmented filamentous bacteria (SFB) are sufficient to support Th17 cell differentiation in mouse, but the molecular and cellular requirements for this process remain incompletely characterized. Here, we show that intestine-draining mesenteric lymph nodes (MLNs), not intestine proper, are the dominant site of SFB-induced intestinal Th17 cell differentiation. Subsequent migration of these cells to the intestinal lamina propria is dependent on their upregulation of integrin ß7. Stat3-dependent induction of RORγt, the Th17 cell-specifying transcription factor, largely depends on IL-6, but signaling through the receptors for IL-21 and IL-23 can compensate for absence of IL-6 to promote SFB-directed Th17 cell differentiation. These results indicate that redundant cytokine signals guide commensal microbe-dependent Th17 cell differentiation in the MLNs and accumulation of the cells in the lamina propria.

Associations between medical students' beliefs about obesity and clinical counseling proficiency.

BACKGROUND: Despite evidence that biological and genetic factors contribute strongly to obesity, many healthcare providers still attribute obesity more to controllable behavioral issues rather than factors outside a person's control. We evaluated whether medical school students' beliefs about obesity correlate with ability to effectively counsel patients with obesity. METHODS: Clerkship-year medical students at NYU School of Medicine completed an Objective Structured Clinical Experience (OSCE) that tests ability to effectively counsel standardized actor-patients with obesity. We surveyed these students to evaluate their beliefs about the causes of obesity and their attitudes towards people with obesity. We analyzed correlations between student beliefs, negative obesity attitudes, and OSCE performance. RESULTS: The response rate was 60.7% (n = 71). When asked to rate the importance of individual factors, students rated controllable factors such as unhealthy diet, physical inactivity, and overeating as more important than genetics or biological factors (p < 0.01). Believing obesity is caused by uncontrollable factors was negatively correlated with obesity bias (r = - 0.447; p < 0.0001). Believing that obesity is caused by factors within a person's control was negatively correlated with counseling skills (r = - 0.235; p < 0.05). CONCLUSIONS: Attribution of obesity to external factors correlated with greater ability to counsel patients with obesity, suggesting that educating providers on the biological causes of obesity could help reduce bias and improve provider care.

Genetic suppression of inflammation blocks the tumor-promoting effects of TGF-ß in gastric tissue.

The contributions of TGF-ß signaling to cancer are complex but involve the inflammatory microenvironment as well as cancer cells themselves. In mice encoding a TGF-ß mutant that precludes its binding to the latent TGF-ß binding protein (Tgfb1(-/C33S)), we observed multiorgan inflammation and an elevated incidence of various types of gastrointestinal solid tumors due to impaired conversion of latent to active TGF-ß1. By genetically eliminating activators of latent TGF-ß1, we further lowered the amount of TGF-ß, which enhanced tumor frequency and multiorgan inflammation. This model system was used to further investigate the relative contribution of TGF-ß1 to lymphocyte-mediated inflammation in gastrointestinal tumorigenesis. Toward this end, we generated Tgfb1(-/C33S);Rag2(-/-) mice that lacked adaptive immune function, which eliminated tumor production. Analysis of tissue from Tgfb1(-/C33S) mice indicated decreased levels of P-Smad3 compared with wild-type animals, whereas tissue from Tgfb1(-/C33S);Rag2(-/-) mice had normal P-Smad3 levels. Inhibiting the inflammatory response normalized levels of interleukin (IL)-1ß and IL-6 and reduced tumor cell proliferation. In addition, Tgfb1(-/C33S);Rag2(-/-) mice exhibited reduced paracrine signaling in the epithelia, mediated by hepatocyte growth factor produced by gastric stroma. Together, our results indicate that many of the responses of the gastric tissue associated with decreased TGF-ß1 may be directly or indirectly affected by inflammatory processes, which accompany loss of TGF-ß1, rather than a direct effect of loss of the cytokine.