Retention Of Lymphocytes Research Articles

Acute myeloid leukemia with peripheral lymph node involvement in dogs: A retrospective study of 23 cases.

Acute myeloid leukemia (AML) can infiltrate extramedullary tissues, such as the liver, spleen, and lymph nodes and can be difficult to differentiate from lymphoma in cytologic and histologic specimens. Our goal was to identify cytologic features that would support a diagnosis of AML in peripheral lymph node aspirates, for which we used the term extramedullary AML (eAML). Medical records of 23 dogs with a diagnosis of AML and archived lymph node aspirate smears from 2016 to 2024 were reviewed across 4 institutions. Inclusion criteria included ≥50% myeloid blasts plus differentiating myeloid cells in lymph node smears, confirmation of myeloid lineage by flow cytometric analysis, and complete medical records. Peripheral lymphadenopathy was the reason for presentation (9/23, 39%) or was found incidentally on physical examination (14/23, 61%). Most dogs were bi- or pancytopenic (18/23, 78%), with blasts identified in blood smears of 18 dogs (78%). Initial lymph node aspirate interpretations included hematopoietic neoplasia (8/21, 38%), AML (6/21, 29%), lymphoma (5/21, 24%), lymphoid hyperplasia (1/21, 5%), and granulocytic precursor infiltrates (1/21, 5%). On lymph node smear review, cytologic features supporting an eAML were differentiating granulocytes, blasts with myeloid features or promonocytes, dysplastic changes in myeloid cells, and retention of residual lymphocytes. The median survival was 22 days (range = 1-360 days), and 69% of 16 dogs given chemotherapy or glucocorticoids lived for 30 days or more. Our study highlights the importance of hemogram results and lymph node aspirate smear examination for morphologic features of myeloid differentiation to help diagnose eAML in lymph node smears.

The effect of immunosuppressive agent FTY-720 on coagulation, nitroxidergic lung activity and water balance in experimental antiphospholipid syndrome

Antiphospholipid syndrome (APS) is a systemic acquired autoimmune thrombophilia that leads to impaired non-respiratory lung functions due to the circulation of antiphospholipid antibodies, shifting the balance between the coagulation link of hemostasis and the anti-coagulation system towards hypercoagulation. The research examines the modulating effect of FTY-720 on the water balance, coagulation and NO-activity of the lungs under conditions of experimental APS. The functional activity of FTY-720 is largely due to its ability to bind to S1P1 receptors and block signaling pathways mediated by the interaction of the mediator sphingosine-1-phosphate with them. The main effect of FTY-720 is immunosuppression, which develops as a result of the drug’s receptor interaction predominantly with S1P1 receptors, resulting in the retention of autoreactive lymphocytes in lymph nodes, and prevents further spread of inflammation and damage. The experiments were conducted on 85 male rats, divided into groups as follows: The first group of animals (n = 30) was injected with cardiolipin antigen every other day for three weeks for APS modeling; the rats of the second group (n = 25), which served as a control group, were similarly injected with 0.9% NaCl; APS modeling and FTY-720 injection were combined on the remaining animals (n = 30). Three weeks later, arterial (art) and venous (ven) blood was taken, in which APTT and PT were determined using a hemocoagulometer CGL 2110 “Solar” and the corresponding coefficients of APPT of ven/art, PT of ven/ art were calculated. NO-activity was assessed by the content of plasma NO and NO bronchoalveolar lavage obtained by washing the extraction of the bronchopulmonary complex in anesthetized animals. To study the water balance of the lungs, the mass of moist and dried lungs was measured, were determined the total, extra- and intravascular fluid of the lungs. In APS, an increase in APTT and PT of arterial and venous blood was observed, an increase in the level of NO in bronchoalveolar lavages against the background of worsening nitroxidergic activity of the lungs – the NO index of ven/art decreased. There was a positive effect of FTY- 720 on the restoration of non-respiratory lung functions in APS.

P738 Response to etrasimod treatment in ulcerative colitis is associated with a reduction of circulating B and pro-inflammatory T cells: a single-cell-based post-hoc sub-analysis of the ELEVATE UC 52 trial

Abstract Background Etrasimod (ETR) is an oral, once-daily, selective sphingosine 1-phosphate receptor 1,4,5 (S1PR) modulator for the treatment of moderately to severely active ulcerative colitis (UC). The mechanism of action is based on a retention of lymphocytes in lymphatic tissue hindering circulating lymphocytes from entering the gut and causing inflammation. However, the effect of ETR on immune cell function and composition is not well characterized. In addition, it is unknown whether the response of UC patients to ETR treatment is associated with specific immune cell signatures. Methods Single-cell RNA sequencing (scRNAseq), mass cytometry (CyTOF) and clinical data integration were used to characterize the effects of 12 weeks of treatment with ETR on the immune composition and function of peripheral blood mononuclear cells (PBMCs) collected from 15 UC patients at weeks 0 and 12 during the ELEVATE UC Phase 3 clinical trial. As an exploratory cohort, PBMCs from 5 UC patients reaching the primary endpoint of clinical remission at week 12 (modified Mayo score <2), 5 UC patients not responding to ETR treatment (modified Mayo score >2) and 5 placebo-treated UC patients were included. 30 samples were processed for scRNAseq; additionally, 28 blood samples were ex-vivo stimulated with ionomycin/PMA for 4 h and cytokine production was assessed by CyTOF. To determine the effects of ETR in UC patients, immune cell function and composition were compared intra-individually between weeks 0 and 12. Subsequent comparisons between ETR responders, non-responders and placebo-treated UC patients were performed to discriminate responders from non-responders. Results Significant reductions in T and B cell subsets, along with increases in the abundance of dendritic and monocytic cells, were observed in responders by week 12 of -treatment. Importantly, ETR treatment significantly reduced circulating T cells producing pro-inflammatory cytokines, including TNFα and IFNγ, and S1PR modulation led to a mitigation of naïve and effector memory CD4 and CD8 T cells in ETR-treated UC patients achieving clinical remission. In contrast, patients not responding to ETR treatment had significantly higher frequencies of both naïve and TNFα-producing CD4 T cells by week 12. Conclusion In line with the described role of S1PR in lymphocyte trafficking, single-cell analyses of circulating immune cells from ETR-treated UC patients confirmed a significant reduction in B cells and pathogenic T cell subsets after ETR treatment providing an in-depth cellular characterization of S1PR modulation in UC patients thereby contributing to a better understanding of the key mechanism of action of ETR. However, these findings require validation in larger cohorts.

Evaluation of Safety and Efficacy of Ruxolitinib in Patients with Pediatric Lymphoproliferative Disorders

Introduction. Pediatric lymphoproliferative disorders (PLPD) encompass a wide spectrum of immune dysregulation conditions with heterogeneous clinical presentation and lab abnormalities. The underlying mechanisms of PLPD are diverse, including dysregulated differentiation of immune cell populations, aberrant recruitment of lymphocyte populations, and/or retention and pathologic survival of lymphocytes. Many PLPD are associated with inborn or acquired genetic factors impacting immune function. Standardized measures to characterize clinical and biological factors in PLPD patients and responses to therapy are lacking. One common feature in PLPD patients is activating IFNg signaling. Ruxolitinib is a drug that blocks hyperactivated IFNg signaling through the JAK-STAT pathway. The goal of this study is to describe the clinical responses of PLPD patients to ruxolitinib. Methods. Medical charts were reviewed to identify patients with PLPD treated with ruxolitnib at Texas Children's Hospital over a 7-year period. Clinical manifestations (recurrent fever, fatigue, lymphadenopathy, recurrent infections, pulmonary disease, endocrinopathy, enteropathy, hepatosplenomegaly, arthritis, CNS symptoms, atopy, dysphagia, underweight), lab values of complete blood count and pathologic inflammation markers (CXCL9, ferritin, sIL2R, IL-18, CD163, neopterin) were categorized with a severity system indicating: 0 no clinical signs and normal lab values; 1 mild to moderate symptoms and abnormal lab values; 2 severe symptoms, highly abnormal lab values (table 1). Total score was computed before and during the addition of ruxolitinib. Complete response (CR) represented a reduction of the total score to 0. Partial response (PR) signified reduction of criteria score ≥ 30% from the baseline with no progression or manifestation of new symptoms. Progression of the disease or improvement < 30% was marked as no response (NR). Results. Chart review identified 19 children and young adults with PLPD who received treatment with ruxolitinib (median age 8.5 years; range 1.2 to 21.6 years). Underlying disease states driving PLPD included HLH, inborn errors of immunity, juvenile rheumatoid arthritis, macrophage activation syndrome, malignant atrophic papulosis of Degos, Aicardi-Goutierres Syndrome, and T-cell large granular lymphocytic leukemia.Genetic variants known or predicted to be damaging were identified in 15 cases (79%), including STAT1, STAT3, TREX1, OFD1, NLRP12, NLRP4, UNC13, PRF1, AP3D1 and mosaic genome-wide paternal uniparental disomy. While 79% of patients received ruxolitinib in combination with other immune suppressants, 21% received only ruxolitinib out of which half received it as front-line therapy. Based on the PLPD Scoring System, overall response rate to ruxolitinib was 73.7%, with 5.3% achieving CR, and 68.4% PR. Overall survival on this study was 84.2% with median 11 months follow-up (range: 0.5 month to 7.1 years). Three patients died due to uncontrolled disease progression. Six patients in whom hematopoietic cell transplant was deemed essential for cure survived to conditioning. Toxicities potentially related to ruxolitinib included grades 1 to 4 cytopenias and grade 1 elevated liver enzymes. Conclusion. PLPD represents a population with overall poor outcomes. We developed standardized staging and response metrics to characterize extent of immune dysregulation and response to therapy. Ruxolitinib represents a potential “precision” therapeutic intervention for patients with pathologic IFNg pathway activation. Ruxolitinib was well-tolerated in this high risk population, and was associated with positive responses in the majority of patients. This study supports expansion of prospective studies to validate the PLPD Scoring System and to optimize therapeutic strategies to manage immune dysregulation, including ruxolitinib.

Combination of Propranolol and a Novel CXCR4 Antagonist Burixafor (GPC-100) for Enhanced Hematopoietic Cell Mobilization

Burixafor (GPC-100), a novel CXCR4 antagonist, has shown safe and effective mobilization of hematopoietic stem and progenitor cells (HSPC) in a phase I clinical study. In multiple myeloma patients, GPC-100 combined with granulocyte-colony stimulating factor (G-CSF) elicited a significant increase in circulating HSPCs that was comparable with the historical results from G-CSF plus the CXCR4 antagonist plerixafor. GPC-100 is currently being investigated for HSPC mobilization in combination with the FDA-approved ß-adrenergic receptor (ß-AR) blocker propranolol in a phase II clinical trial for autologous stem cell transplant (ASCT) in multiple myeloma. Here, we present preclinical findings indicating that the addition of propranolol to GPC-100 alone or GPC-100 and G-CSF combination can address the unmet needs of patients undergoing mobilization. Additionally, we show an enhanced and unique pattern of lymphoid cell mobilization that may have applications in adoptive cell therapies. Compared to chemotherapy, ASCT significantly improves survival in multiple myeloma patients. Because HSPCs constitute a very small fraction (~ 0.1%) of circulating mononuclear cells, it is critical to mobilize a sufficient number of HSPC into peripheral blood during the ASCT process. Current therapies for HSPC mobilization include G-CSF as a monotherapy or combined with plerixafor. However, mobilization failure is experienced by 15-50% patients, leading to potential loss of ASCT as a treatment option and significant toxicity from repeated mobilization attempts. Moreover, G-CSF is contraindicated in sickle cell disease and may exacerbate autoimmune diseases. Therefore, our goal is to identify novel strategies that will not only address the mobilization failure, but also explore non-G-CSF options for adequate mobilization. G protein-coupled receptors like CXCR4 can form heteromers with other receptors and result in altered signaling pathways. Using Proximity Ligation Assay in Namalwa (lymphoma) cells, we show that endogenously expressed CXCR4 and ß 2AR form heteromers, which are absent in CXCR4 knockout cells. In cell-based assays, co-activation of both receptors with their respective ligands, CXCL12 and epinephrine, leads to a synergistic increase in calcium flux (Figure 1) as well as ß-arrestin recruitment, indicating functional consequences of the heteromerization. Complete blockade of this enhanced signaling is only achieved with co-inhibition by both antagonists. Like CXCR4, ß 2AR is also expressed by HSPCs, and in lymph nodes was shown to heteromerize with CXCR4 to increase lymphocyte retention. In multiple myeloma patients, propranolol upregulated stem-cell like gene signature. Therefore, we sought to understand the effects of propranolol on HSPC mobilization by GPC-100. In mice, single injection of GPC-100 effectively mobilized hematopoietic stem cells characterized as Lin negSca1 +cKit +(LSK) cells as well as mature Lin negCD34 + progenitor cells by 2-4-fold, respectively. Seven-day pretreatment with propranolol enhanced LSK cell mobilization by GPC-100 resulting in a 4-fold increase in circulating HSPCs (Figure 2). Addition of propranolol to G-CSF and GPC-100 led to 8-17-fold increases in mobilization of long-term repopulating HSCs (CD34 negLSK and CD150 +LSK), which were greater than the 4-7-fold increases elicited by G-CSF and G-CSF with plerixafor. Additionally, propranolol enhanced GPC-100 induced mobilization of white blood cells, neutrophils, and lymphocytes (Figure 2). Immune cell subset analyses revealed that GPC-100 induced a 3-fold increase in circulating CD8 +T cells, which was increased to 7-fold when combined with propranolol (Figure 2). For comparison, plerixafor increased CD8 + T cell mobilization by only 2-fold. GPC-100 induced mobilization of NK and B cells was also improved by propranolol. These pre-clinical data support our phase II clinical trial currently in progress (NCT05561751). In the first arm of this two-arm trial, GPC-100 is combined with orally administered propranolol, and in the second arm, G-CSF is added to this combination. We anticipate that our clinical studies can fill the gap in the current standard of care without adding a significant financial burden or co-morbidities. Furthermore, enhanced mobilization of CD8+ T cells can provide extended opportunities for improved adoptive cell therapies.

Lymphocyte migration and retention properties affected by ibrutinib in chronic lymphocytic leukemia.

The Bruton tyrosine kinase (BTK) inhibitor ibrutinib is widely used for treatment of patients with relapsed/refractory or treatment-naïve chronic lymphocytic leukemia (CLL). A prominent effect of ibrutinib is to disrupt the retention of CLL cells from supportive lymphoid tissues, by altering BTK-dependent adhesion and migration. To further explore the mechanism of action of ibrutinib and its potential impact on non-leukemic cells, we quantified multiple motility and adhesion parameters of human primary CLL cells and non-leukemic lymphoid cells. In vitro, ibrutinib affected CCL19-, CXCL12- and CXCL13-evoked migration behavior of CLL cells and non-neoplastic lymphocytes, by reducing both motility speed and directionality. De-phosphorylation of BTK induced by ibrutinib in CLL cells was associated with defective polarization over fibronectin and inability to assemble the immunological synapse upon B-cell receptor engagement. In patients' samples collected during a 6-month monitoring of therapy, chemokine-evoked migration was repressed in CLL cells and marginally reduced in T cells. This was accompanied by profound modulation of the expression of chemokine receptors and adhesion molecules. Remarkably, the relative expression of the receptors governing lymph node entry (CCR7) versus exit (S1PR1) stood out as a reliable predictive marker of the clinically relevant treatment-induced lymphocytosis. Together, our data reveal a multifaceted modulation of motility and adhesive properties of ibrutinib on both CLL leukemic cell and T-cell populations and point to intrinsic differences in CLL recirculation properties as an underlying cause for variability in treatment response.

P558 Etrasimod for the treatment of ulcerative colitis: analysis of infection rates from the phase 3 ELEVATE UC 52 and ELEVATE UC 12 clinical trials

Abstract Background Infections are an important safety concern in patients with IBD and may be due to its therapies, such as corticosteroids. Etrasimod is an investigational, once-daily, oral, selective sphingosine 1-phosphate receptor 1,4,5 (S1P1,4,5) modulator in development for the treatment of moderately to severely active ulcerative colitis (UC). The biologic effect of etrasimod leads to selective and reversible lymphocyte retention in lymph nodes with a decrease in peripheral lymphocyte count. We report the infection events from the phase 3 ELEVATE programme. Methods Infection events were evaluated in the pivotal UC pooled safety analyses set comprising two phase 3 studies: ELEVATE UC 52 (NCT03945188) and ELEVATE UC 12 (NCT03996369). Subjects (16-80 years) with moderately to severely active UC were randomised 2:1 to once-daily etrasimod 2 mg or placebo (PBO). We report the n (%) and exposure-adjusted incidence rate (EAIR) of infections including serious infections, severe infections, opportunistic infections (including tuberculosis), and herpes infections. Infections were considered adverse events of special interest (AESI) if they were severe (≥ CTCAE Grade 3), were opportunistic infections, or were herpes zoster or herpes simplex infections. Results From the pooled ELEVATE UC 12 and ELEVATE UC 52 trials, 527 subjects received ≥1 dose of etrasimod 2 mg (265.6 subject-years of exposure) and 260 subjects were randomised to PBO (103.0 subject-years of exposure). Infections were similar between treatment groups (etrasimod: 99 [18.8%], EAIR=0.41; PBO: 46 [17.7%], EAIR=0.52). The most frequent infections in both groups were COVID-19, urinary tract infections, and nasopharyngitis (Table 1). Serious infections occurred in 3 (0.6%) subjects in the etrasimod arm (EAIR=0.01) and 5 (1.9%) in PBO arm (EAIR=0.05). Two cases of herpes zoster were reported in each treatment group (etrasimod: 0.4%, EAIR<0.01; PBO: 0.8%, EAIR=0.02); these were localised and nonserious. One opportunistic infection was reported in each arm (etrasimod: subject withdrew from the study on day 20, the AE of Cytomegalovirus infection [Grade 2] was reported on day 36; PBO: tuberculosis [Grade 2]). Overall, 3 cases of infection led to discontinuation: 2 in the etrasimod arm (both mild) and 1 in the PBO arm (Table 2). No subject with an absolute lymphocyte count <0.2×109/L subsequently reported a serious/severe or opportunistic infection. There were no deaths. Conclusion In these trials, etrasimod-treated subjects reported no increase in infections relative to PBO. Serious infections and herpes zoster were more commonly reported in the PBO-treated group. Longer-term follow-up data from the ongoing 5-year open-label extension will further characterize the etrasimod safety profile.

CD103+ Cells and Chemokine Receptor Expression in Breast Cancer.

Mucosal environments harbour lymphocytes, which express several adhesion molecules, including intestinal homing receptors and integrin αE/β7 (CD103). CD103 binds E-cadherin, an integrin receptor expressed in intestinal endothelial cells. Its expression not only enables homing or retention of T lymphocytes at these sites but is also associated with increased T lymphocyte activation. However, it is not yet clear how CD103 expression is related to the clinical staging of breast cancer, which is determined by factors such as the size of the tumor (T), the involvement of nearby lymph nodes (N), and presence of metastasis (M). We examined the prognostic significance of CD103 by FACS in 53 breast cancer patients and 46 healthy controls enrolled, and investigated its expression, which contributes to lymphocyte recruitment in tumor tissue. Patients with breast cancer showed increased frequencies of CD103+, CD4+CD103+, and CD8+CD103+ cells compared to controls. CD103 was expressed at a high level on the surfaces of tumor-infiltrating lymphocytes in patients with breast cancer. Its expression in peripheral blood was not correlated with clinical TNM stage. To determine the localisation of CD103+ cells in breast tissue, tissue sections of breast tumors were stained for CD103. In tissue sections of breast tumors stained for CD103, its expression in T lymphocytes was higher compared to normal breast tissue. In addition, CD103+ cells expressed higher levels of receptors for inflammatory chemokines, compared to CD103- cells. CD103+ cells in peripheral blood and tumor tissue might be an important source of tumor-infiltrating lymphocyte trafficking, homing, and retention in cancer patients.

UROLITHIN A: GUT-BRAIN DIETARY INTERVENTION IN PARKINSON'S DISEASE

Abstract Gastrointestinal dysfunction is amongst the most common prodromal symptoms of Parkinson’s disease (PD). Pathological alpha-synuclein has been detected in the intestines prior to disease onset, and a leaky gut is also implicated in its etiology. Thus, we hypothesized that modulation of the gut microbiome and intestinal immune milieu via early dietary intervention may act to mitigate PD pathogenesis. Urolithin A (UA) is a gut metabolite shown to ameliorate geriatric diseases by increasing mitophagy and dampening inflammation. The aim of our study is to elucidate its mechanism of action and therapeutic efficacy in PD, which to date is unclear. Preliminary flow cytometric data demonstrates that administration of a UA-diet significantly increased the proportion of colonic gamma-delta (γδ) T cells in nine-month-old Thy-1 α-syn mice, which are downregulated relative to non-transgenics on a non-UA control diet. PD patients have been reported to have higher levels of γδ T cells in their cerebrospinal fluid and, while little is known about colonic γδ Ts in the context of PD, these cells are anti-inflammatory and responsible for intestinal repair in several colitis models. Our data suggests a retention of lymphocytes involved in the targeted migration from the gut to the brain, which may contribute to gut epithelial integrity. Proportion of induced regulatory T cells in peripheral blood, which are critical for immune tolerance, also increased significantly with a UA-diet. In addition, UA-fed mice showed a slight improvement in novel object recognition. Additional analyses are underway to comprehensively evaluate the impact of UA on PD pathology.

The multifunctional nature of CD103 (αEβ7 integrin) signaling in tissue-resident lymphocytes.

Intestinal tissue-resident lymphocytes are critical for maintenance of the mucosal barrier and to prevent enteric infections. The activation of these lymphocytes must be tightly regulated to prevent aberrant inflammation and epithelial damage observed in autoimmune diseases, yet also ensure that antimicrobial host defense remains uncompromised. Tissue-resident lymphocytes express CD103, or αE integrin, which dimerizes with the β7 subunit to bind to E-cadherin expressed on epithelial cells. Although the role of CD103 in homing and retention of lymphocytes to and within peripheral tissues has been well characterized, the molecular signals activated following CD103 engagement remain understudied. Here, we highlight recent studies that elucidate the functional contribution of CD103 in various lymphocyte subpopulations, either as an independent signaling molecule or in the context of TCR co-stimulation. Finally, we will discuss the gaps in our understanding of CD103 biology and the therapeutic potential of targeting CD103 on tissue-resident lymphocytes.

Global Phase 3, Randomized, Placebo-Controlled Trial with Open-Label Extension Evaluating the Oral CXCR4 Antagonist Mavorixafor in Patients with WHIM Syndrome (4WHIM): Trial Design and Enrollment

Global Phase 3, Randomized, Placebo-Controlled Trial with Open-Label Extension Evaluating the Oral CXCR4 Antagonist Mavorixafor in Patients with WHIM Syndrome (4WHIM): Trial Design and Enrollment

Regulation and Role of αE Integrin and Gut Homing Integrins in Migration and Retention of Intestinal Lymphocytes during Inflammatory Bowel Disease.

Targeting interactions between α4β7 integrin and endothelial adhesion molecule MAdCAM-1 to inhibit lymphocyte migration to the gastrointestinal tract is an effective therapy in inflammatory bowel disease (IBD). Following lymphocyte entry into the mucosa, a subset of these cells expresses αEβ7 integrin, which is expressed on proinflammatory lymphocytes, to increase cell retention. The factors governing lymphocyte migration into the intestinal mucosa and αE integrin expression in healthy subjects and IBD patients remain incompletely understood. We evaluated changes in factors involved in lymphocyte migration and differentiation within tissues. Both ileal and colonic tissue from active IBD patients showed upregulation of ICAM-1, VCAM-1, and MAdCAM-1 at the gene and protein levels compared with healthy subjects and/or inactive IBD patients. β1 and β7 integrin expression on circulating lymphocytes was similar across groups. TGF-β1 treatment induced expression of αE on both β7+ and β7- T cells, suggesting that cells entering the mucosa independently of MAdCAM-1/α4β7 can become αEβ7+ ITGAE gene polymorphisms did not alter protein induction following TGF-β1 stimulation. Increased phospho-SMAD3, which is directly downstream of TGF-β, and increased TGF-β-responsive gene expression were observed in the colonic mucosa of IBD patients. Finally, in vitro stimulation experiments showed that baseline β7 expression had little effect on cytokine, chemokine, transcription factor, and effector molecule gene expression in αE+ and αE- T cells. These findings suggest cell migration to the gut mucosa may be altered in IBD and α4β7-, and α4β7+ T cells may upregulate αEβ7 in response to TGF-β once within the gut mucosa.

Sphingosine 1-phosphate receptor 5 (S1PR5) regulates the peripheral retention of tissue-resident lymphocytes.

Tissue-resident memory T (TRM) cells provide long-lasting immune protection. One of the key events controlling TRM cell development is the local retention of TRM cell precursors coupled to downregulation of molecules necessary for tissue exit. Sphingosine-1-phosphate receptor 5 (S1PR5) is a migratory receptor with an uncharted function in T cells. Here, we show that S1PR5 plays a critical role in T cell infiltration and emigration from peripheral organs, as well as being specifically downregulated in TRM cells. Consequentially, TRM cell development was selectively impaired upon ectopic expression of S1pr5, whereas loss of S1pr5 enhanced skin TRM cell formation by promoting peripheral T cell sequestration. Importantly, we found that T-bet and ZEB2 were required for S1pr5 induction and that local TGF-β signaling was necessary to promote coordinated Tbx21, Zeb2, and S1pr5 downregulation. Moreover, S1PR5-mediated control of tissue residency was conserved across innate and adaptive immune compartments. Together, these results identify the T-bet-ZEB2-S1PR5 axis as a previously unappreciated mechanism modulating the generation of tissue-resident lymphocytes.

Dual targeting of lymphocyte homing and retention through α4β7 and αEβ7 inhibition in inflammatory bowel disease

SummaryAnti-integrins are therapeutically effective for inflammatory bowel disease, yet the relative contribution of α4β7 and αEβ7 to gut lymphocyte trafficking is not fully elucidated. Here, we evaluate the effect of α4β7 and αEβ7 blockade using a combination of murine models of gut trafficking and longitudinal gene expression analysis in etrolizumab-treated patients with Crohn's disease (CD). Dual blockade of α4β7 and αEβ7 reduces CD8+ T cell accumulation in the gut to a greater extent than blockade of either integrin alone. Anti-αEβ7 reduces epithelial:T cell interactions and promotes egress of activated T cells from the mucosa into lymphatics. Inflammatory gene expression is greater in human intestinal αEβ7+ T cells. Etrolizumab-treated patients with CD display a treatment-specific reduction in inflammatory and cytotoxic intraepithelial lymphocytes (IEL) genes. Concurrent blockade of α4β7 and αEβ7 promotes reduction of cytotoxic IELs and inflammatory T cells in the gut mucosa through a stepwise inhibition of intestinal tissue entry and retention.

Integrin β7 Inhibits Colorectal Cancer Pathogenesis via Maintaining Antitumor Immunity.

Immune cell infiltration is important for predicting the clinical outcomes of colorectal cancer. Integrin β7 (ITGB7), which is expressed on the surface of leukocytes, plays an essential role in the homing of immune cells to gut-associated lymphoid tissue and facilitating the retention of lymphocytes in gut epithelium; however, its role in colorectal cancer pathogenesis is poorly explored. Here, we found that the number of β7+ cells decreased significantly in tumor tissue compared with adjacent normal tissue. β7 expression decreased in tumor-derived compared with normal tissue-derived CD8+ T cells. With bulk RNA expression data from public platforms, we demonstrated that higher ITGB7 expression correlated with longer patient survival, higher cytotoxic immune cell infiltration, lower somatic copy-number alterations, decreased mutation frequency of APC and TP53, and better response to immunotherapy. The possible cell-cell interactions mediated by ITGB7 and its ligands MAdCAM-1, VCAM-1, and CDH1 were investigated using public single-cell RNA sequencing data. ITGB7 deficiency led to exaggerated tumorigenesis and progression in both Apcmin /+ spontaneous and MC38 orthotopic models of colorectal cancer, which could be due to a reduced infiltration of activated CD8+ T cells, effector memory CD8+ T cells, IFNγ+ CD8+ T cells, IFNγ+ natural killer cells, CD103+ dendritic cells, and other immune cell subsets that are essential players in antitumor immunity. In conclusion, our data revealed that ITGB7 could inhibit the tumorigenesis and progression of colorectal cancer by maintaining antitumor immunity.

The Dynamic Entropy of Tumor Immune Infiltrates: The Impact of Recirculation, Antigen-Specific Interactions, and Retention on T Cells in Tumors.

Analysis of tumor infiltration using conventional methods reveals a snapshot view of lymphocyte interactions with the tumor environment. However, lymphocytes have the unique capacity for continued recirculation, exploring varied tissues for the presence of cognate antigens according to inflammatory triggers and chemokine gradients. We discuss the role of the inflammatory and cellular makeup of the tumor environment, as well as antigen expressed by cancer cells or cross-presented by stromal antigen presenting cells, on recirculation kinetics of T cells. We aim to discuss how current cancer therapies may manipulate lymphocyte recirculation versus retention to impact lymphocyte exclusion in the tumor.

Fibroblasts upregulate expression of adhesion molecules and promote lymphocyte retention in 3D fibroin/gelatin scaffolds

Bioengineered scaffolds are crucial components in artificial tissue construction. In general, these scaffolds provide inert three-dimensional (3D) surfaces supporting cell growth. However, some scaffolds can affect the phenotype of cultured cells, especially, adherent stromal cells, such as fibroblasts. Here we report on unique properties of 3D fibroin/gelatin materials, which may rapidly induce expression of adhesion molecules, such as ICAM-1 and VCAM-1, in cultured primary murine embryonic fibroblasts (MEFs). In contrast, two-dimensional (2D) fibroin/gelatin films did not show significant effects on gene expression profiles in fibroblasts as compared to 3D culture conditions. Interestingly, TNF expression was induced in MEFs cultured in 3D fibroin/gelatin scaffolds, while genetic or pharmacological TNF ablation resulted in diminished ICAM-1 and VCAM-1 expression by these cells. Using selective MAPK inhibitors, we uncovered critical contribution of JNK to 3D-induced upregulation of these adhesion molecules. Moreover, we observed ICAM-1/VCAM-1-dependent adhesion of lymphocytes to fibroblasts cultured in 3D fibroin/gelatin scaffolds, but not on 2D fibroin/gelatin films, suggesting functional reprogramming in stromal cells, when exposed to 3D environment. Finally, we observed significant infiltration of lymphocytes into 3D fibroin/gelatin, but not into collagen scaffolds in vivo upon subcapsular kidney implantation in mice. Together our data highlight the important features of fibroin/gelatin scaffolds, when they are produced as 3D sponges rather than 2D films, which should be considered when using these materials for tissue engineering.

GPR56 inhibits chemotaxis of human Natural Killer and TEMRA lymphocytes

Abstract Within the human immune system, the expression of GPR56, an adhesion G-protein couple receptor, is restricted to cytotoxic Natural Killer (NK) and T lymphocytes, including T effector memory re-expressing CD45RA (TEMRA) cells. In primary NK cells, GPR56 acts as an inhibitory receptor, as it diminishes their ability to eliminate target cells. Overexpression of GPR56 in immortal NK-92 cells also leads to robust inhibition of cell chemotaxis. GPR56 is speculated to promote retention of cytotoxic lymphocytes in inflamed peripheral tissues. Thus, GPR56 has the potential to regulate immune responses that may lead to excessive inflammation and autoimmunity. The aim of the present study was, therefore, to examine whether GPR56 mediates cytotoxic immune cell functions and whether GPR56 expression is altered in autoimmune diseases. To tackle these questions, we first compared expression of GPR56 in healthy and autoimmune disease patient tissues using scRNA-seq datasets. Next, we tested whether stimulation of GPR56 with a monoclonal antibody modulated the migratory capacity of NK and CD8+ TEMRA cells. We found that chemotaxis toward CXCL12, IL-8, and CX3CL1 was strikingly inhibited by GPR56. Using bulk RNA-seq, we found GPR56-stimulation impacted a multitude of signaling cascades that regulate cell chemotaxis. Taken together, our results confirm that GPR56 is a marker for NK and TEMRA cells in healthy and autoimmune patient tissues and establish GPR56 as a key regulator of lymphocyte chemotaxis.

Combined blockade of α4β7 and αEβ7 integrins leads to a greater reduction of gut proinflammatory T lymphocytes over either pathway alone

Abstract Therapeutic approaches to treat inflammatory bowel diseases (IBD) include targeting integrins that mediate adhesion and migration of lymphocytes to the gastrointestinal (GI) tract. Etrolizumab is a humanized monoclonal antibody that selectively binds the β7 subunit of the heterodimeric integrins of α4β7 and αEβ7. The relative contribution of α4β7 and αEβ7 integrin family members to lymphocyte migration and retention in GI tractremains to be characterized. Here we applied single-cell technologies to healthy and IBD patient biopsies and found that αEβ7 is highly expressed in a subset of proinflammatory CD4+T cells and majority of cytotoxic intraepithelial CD8+T cells. In order to understand the role of αEβ7 in gut T cell accumulation, we used a photo-convertible reporter system to determine that concurrent inhibition of α4β7 and αEβ7 together led to a greater reduction of polyclonal or antigen specific T cell accumulation in the intestinal mucosa and epithelium compared to single blockade of either α4β7 or αEβ7. Further intra-vital two-photon microscopy and photo-specific labeling experiments revealed that blockade of αEβ7 reduces T cell interactions with basolateral epithelial surface, increases the migratory speed of activated T cells in the intestinal mucosa, and facilitates effector T cell egress from the intestinal mucosal through lymphatic vessels. Our data suggests co-blockade of α4β7 and αEβ7 together offers a superior inhibition of T cell accumulation in gastrointestinal tissues through a stepwise inhibition of T cell migration and subsequent tissue retention.

YAP and TAZ in Fibroblastic Reticular Cells Support Hematopoiesis and Retention of Lymphocytes in Lymph Nodes

INTRODUCTION: Fibroblastic reticular cells (FRCs) are essential for adaptive immune response and maintaining lymph node (LN) homeostasis. FRCs regulate immune cell entry into the LN and confer compartmentalization of lymphocytes by secretion of essential chemokines. Indeed, FRCs are activated and display an undifferentiated phenotype in LN of patients with follicular lymphoma, but their meaning and mode action are unclear. The mammalian Hippo signaling pathway is an essential regulator of cell fate, differentiation, and homeostasis. Its final downstream effectors YAP and TAZ (YAP/TAZ) are inhibited by LATS1 and LATS2 (LATS1/2) in a phosphorylation-dependent manner. The roles of YAP/TAZ in hematopoiesis are considered to be dispensable under healthy physiological condition, but their significance appears to be context dependent in pathologies including hematologic malignancies. OBJECTIVES: We hypothesized that the Hippo pathway plays important roles in regulating FRCs by interacting with lymphocytes, with relevance to structural and functional properties of LNs. Using FRC-specific YAP/TAZ depletion or hyperactivation mouse models, we sought to investigate the roles of YAP/TAZ in orchestrating lymphocyte homeostasis by FRCs. METHODS: Animal care and experimental procedures were performed under the approval of the Institutional Animal Care and Use Committee (KA2016-12) of KAIST. Yap/Taz∆FRC or Lats1/2∆FRC mouse were generated by crossing FRC-specific Ccl19-Cre or inducible Pdgfrb-Cre-ERT2 mouse with Yapfl/fl/Tazfl/fl or Lats1fl/fl/Lats2fl/fl mouse, respectively. Cre-ERT2-negative but flox/flox-positive littermates were defined as wild-type mice (WT). In order to induce Cre activity, 2 mg of tamoxifen (Sigma-Aldrich) was dissolved in corn oil and intra-peritoneally injected for four consecutive days. Skin-draining LNs were analyzed with immunofluorescence staining, flow cytometry, or fluorescence activated cell sorting. Chemokine expression was measured from sorted FRCs with qRT-PCR, immunoblotting, or ELISA. APC BrdU flow kit (BD Biosciences) was used for cell cycle analysis. Blood count in mice was measured with hemocytometer (pocH-100iV DiFF, Sysmex). RESULTS: Both YAP/TAZ were highly and equally distributed in nucleus and cytoplasm of mouse LN FRCs, in addition to blood and lymphatic endothelial cells. LNs of Yap/Taz∆FRC mice compared with WT revealed a slight reduction in LN weight and reduced total cell number (~64.9%), decreased proportion (~42.9%), and number (~61.1 %) of FRCs among CD45- stromal cells, which were less proliferative (~65.2%) but had no difference in apoptosis. However, neither proliferation nor apoptosis of immune cells was altered. Analysis of isolated FRCs revealed that mRNA levels of lymphoid chemokines for immune cell trafficking and function were significantly attenuated in Yap/TazΔFRC mice compared with WT. Intriguingly, Lats1/2∆FRC mice looked pale from 1 week after birth. We found lower red blood cell (RBC) count (~16.1%) with decreased concentration of hemoglobin (~25.8%) in Lats1/2∆FRC mice compared with WT, suggesting hypochromic anemia. Moreover, although whole body length and overall organ size were small in Lats1/2∆FRC mice compared with WT at 2 weeks after birth, we could not observe any gross or microscopic abnormalities in major organs including brain, heart, lung, liver, and kidney in Lats1/2∆FRC mice. We further analyzed the primary lymphoid organ thymus and the secondary lymphoid organ spleen, as they are both supported by CCL19+ FRCs. Similar to major organs, the overall size of thymus and spleen was smaller in Lats1/2∆FRC mice compared with WT at 2 weeks after birth. However, microscopic analysis of thymus revealed that the border between the cortex and medulla was disrupted by the expanded medulla at the periphery that blends into the surrounding cortex in Lats1/2∆FRC mice, and analysis of spleen also revealed unclear lymphoid follicles with significantly reduced number of immune cells within the expanded white pulp in Lats1/2∆FRC mice compared with WT. CONCLUSIONS: Our findings present YAP/TAZ as essential governors of FRCs by supporting hematopoiesis and lymphocyte homeostasis. Considering that YAP/TAZ are enriched in bone marrow stromal cells, additional work to elucidate their role in promoting bone marrow microenvironment will improve our understanding on hematopoietic stem cell niche. Disclosures No relevant conflicts of interest to declare.