Regulation of chemokine-induced transendothelial migration of T lymphocytes by endothelial activation: differential effects on naive and memory T cells

TET2-mediated tumor cGAS triggers endothelial STING activation to regulate vasculature remodeling and anti-tumor immunity in liver cancer

Induction of tumor vascular normalization is a crucial measure to enhance immunotherapy efficacy. cGAS-STING pathway is vital for anti-tumor immunity, but its role in tumor vasculature is unclear. Herein, using preclinical liver cancer models in Cgas/Sting-deficient male mice, we report that the interdependence between tumor cGAS and host STING mediates vascular normalization and anti-tumor immune response. Mechanistically, TET2 mediated IL-2/STAT5A signaling epigenetically upregulates tumor cGAS expression and produces cGAMP. Subsequently, cGAMP is transported via LRRC8C channels to activate STING in endothelial cells, enhancing recruitment and transendothelial migration of lymphocytes. In vivo studies in male mice also reveal that administration of vitamin C, a promising anti-cancer agent, stimulates TET2 activity, induces tumor vascular normalization and enhances the efficacy of anti-PD-L1 therapy alone or in combination with IL-2. Our findings elucidate a crosstalk between tumor and vascular endothelial cells in the tumor immune microenvironment, providing strategies to enhance the efficacy of combinational immunotherapy for liver cancer.

CTLs Get SMAD When Pathogens Tell Them Where to Go

Vaccines protect against infections by eliciting both Ab and T cell responses. Because the immunity wanes as protective epitopes get modified by accruing mutations, developing strategies for immunization against new variants is a major priority for vaccine development. CTLs eliminate cells that support viral replication and provide protection against new variants by targeting epitopes from internal viral proteins. This form of protection has received limited attention during vaccine development, partly because reliable methods for directing pathogen-specific memory CD8 T cells to vulnerable tissues are currently unavailable. In this review we examine how recent studies expand our knowledge of mechanisms that contribute to the functional diversity of CTLs as they respond to infection. We discuss the role of TGF-β and the SMAD signaling cascade during genetic programming of pathogen-specific CTLs and the pathways that promote formation of a newly identified subset of terminally differentiated memory CD8 T cells that localize in the vasculature.

SMAD4 and TGFβ are architects of inverse genetic programs during fate-determination of antiviral CTLs

Transforming growth factor β (TGFβ) is an important differentiation factor for cytotoxic T lymphocytes (CTLs) and alters the expression levels of several of homing receptors during infection. SMAD4 is part of the canonical signaling network used by members of the transforming growth factor family. For this study, genetically modified mice were used to determine how SMAD4 and TGFβ receptor II (TGFβRII) participate in transcriptional programming of pathogen-specific CTLs. We show that these molecules are essential components of opposing signaling mechanisms, and cooperatively regulate a collection of genes that determine whether specialized populations of pathogen-specific CTLs circulate around the body, or settle in peripheral tissues. TGFβ uses a canonical SMAD-dependent signaling pathway to downregulate Eomesodermin (EOMES), KLRG1, and CD62L, while CD103 is induced. Conversely, in vivo and in vitro data show that EOMES, KLRG1, CX₃CR1, and CD62L are positively regulated via SMAD4, while CD103 and Hobit are downregulated. Intravascular staining also shows that signaling via SMAD4 promotes formation of long-lived terminally differentiated CTLs that localize in the vasculature. Our data show that inflammatory molecules play a key role in lineage determination of pathogen-specific CTLs, and use SMAD-dependent signaling to alter the expression levels of multiple homing receptors and transcription factors with known functions during memory formation.

Dual role of endothelial Myct1 in tumor angiogenesis and tumor immunity

The cross-talk between angiogenesis and immunity within the tumor microenvironment (TME) is critical for tumor prognosis. While pro-angiogenic and immunosuppressive TME promote tumor growth, anti-angiogenic and immune stimulatory TME inhibit tumor progression. Therefore, there is a great interest in achieving vascular normalization to improve drug delivery and enhance antitumor immunity. However, anti-vascular endothelial growth factor (VEGF) mechanisms to normalize tumor vessels have offered limited therapeutic efficacies for patients with cancer. Here, we report that Myct1, a direct target of ETV2, was nearly exclusively expressed in endothelial cells. In preclinical mouse tumor models, Myct1 deficiency reduced angiogenesis, enhanced high endothelial venule formation, and promoted antitumor immunity, leading to restricted tumor progression. Analysis of The Cancer Genome Atlas (TCGA) datasets revealed a significant (P < 0.05) correlation between MYCT1 expression, angiogenesis, and antitumor immunity in human cancers, as suggested by decreased FOXP3 expression and increased antitumor macrophages in patients with low MYCT1 expression. Mechanistically, MYCT1 interacted with tight junction protein Zona Occludens 1 and regulated Rho GTPase-mediated actin cytoskeleton dynamics, thereby promoting endothelial motility in the angiogenic environment. Myct1-deficient endothelial cells facilitated trans-endothelial migration of cytotoxic T lymphocytes and polarization of M1 macrophages. Myct1 targeting combined with anti-PD1 treatment significantly (P < 0.05) increased complete tumor regression and long-term survival in anti-PD1-responsive and -refractory tumor models in mice. Our data collectively support a critical role for Myct1 in controlling tumor angiogenesis and reprogramming tumor immunity. Myct1-targeted vascular control, in combination with immunotherapy, may become an exciting therapeutic strategy.

Meta-Analysis on Associations of RGS1 and IL12A Polymorphisms with Celiac Disease Risk

The pathogenesis of celiac disease (CD) has been related to polymorphisms in the regulator of G-protein signaling 1 (RGS1) and interleukin-12 A (IL12A) genes, but the existing findings are inconsistent. Our aim is to investigate the associations of two single-nucleotide polymorphisms (SNPs) (rs2816316 in RGS1 and rs17810546 in IL12A) with CD risk using meta-analysis. We searched PubMed and Web of Science on RGS1 rs2816316 and IL12A rs17810546 with CD risk. Odds ratio (OR) and 95% confidence interval (CI) of each SNP were estimated. All statistical analyses were performed on Stata 12.0. A total of seven studies were retrieved and analyzed. The available data indicated the minor allele C of rs2816316 was negatively associated with CD (C vs. A: OR = 0.77, 95% CI = 0.74-0.80), and a positive association was found for the minor allele G of rs17810546 (G vs. A: OR = 1.37, 95% CI = 1.31-1.43). The co-dominant model of genotype effect confirmed the significant associations between RGS1 rs2816316/IL12A rs17810546 and CD. No evidence of publication bias was observed. Our meta-analysis supports the associations of RGS1 and IL12A with CD and strongly calls for further studies to better understand the roles of RGS1 and IL12A in the pathogenesis of CD.

Dynamic motile T cells highly respond to the T cell stimulation via PI3K-Akt and NF-κB pathways

T lymphocytes (T cells) circulate from the blood into secondary lymphoid organs for immune surveillance. In this study, we hypothesized that circulating T cells are heterogeneous and can be grouped according to their differential migratory capacity in response to chemoattractants, rather than expressions of certain receptors or cytokines. We further hypothesized that, at least in part, this intrinsic difference in motility may be related to the T cell function. We established motile (m-T) and non-motile T (nm-T) cell lines based on their response to the chemokine SDF-1α. m-T cells showed more irregular and polarized morphologies than nm-T cells did. Interestingly, m-T cells produced higher levels of IL-2, a marker for T cell activation, than nm-T cells did after stimulation; however, no differences were observed in terms of surface expression of T cell receptors (TCR), adhesion molecules LFA-1 and ICAM-1, and chemokine receptor CXCR4. Both cell lines also showed similar membrane events (i.e., T cell-APC conjugation, LFA-1 accumulation at the immunological synapse, and TCR internalization). In contrast, PKC-θ, a downstream of PI3K-Akt pathway was constitutively activated in m-T cells and the activation was more prominent during T cell stimulation. Consequently, NF-κB activity was selectively upregulated in m-T cells. This study is the first, to our knowledge, to demonstrate that T cells can be subcategorized on the basis of their intrinsic migratory capacity in relation to T cell activation.

IL-1 enhances expansion, effector function, tissue localization, and memory response of antigen-specific CD8 T cells

Here, we show that interleukin-1 (IL-1) enhances antigen-driven CD8 T cell responses. When administered to recipients of OT-I T cell receptor transgenic CD8 T cells specific for an ovalbumin (OVA) peptide, IL-1 results in an increase in the numbers of wild-type but not IL1R1^−/− OT-I cells, particularly in spleen, liver, and lung, upon immunization with OVA and lipopolysaccharide. IL-1 administration also results in an enhancement in the frequency of antigen-specific cells that are granzyme B⁺, have cytotoxic activity, and/ or produce interferon γ (IFN-γ). Cells primed in the presence of IL-1 display enhanced expression of granzyme B and increased capacity to produce IFN-γ when rechallenged 2 mo after priming. In three in vivo models, IL-1 enhances the protective value of weak immunogens. Thus, IL-1 has a marked enhancing effect on antigen-specific CD8 T cell expansion, differentiation, migration to the periphery, and memory.

Differential regulation of CD4+ T cell adhesion to cerebral microvascular endothelium by the β-chemokines CCL2 and CCL3

In Multiple sclerosis (MS), circulating lymphocytes cross the blood–brain barrier (BBB) and accumulate at sites of antigenic challenge. This process depends on specific interactions between lymphocytes and cerebral microvascular endothelium that involve endothelial activation by cytokines and the presence of chemokines. Chemokines play a key role in the orchestration of immune responses, acting both as chemoattractants and activators of leukocyte subsets. In the present study, we investigated the effects of the β-chemokines, CCL2 and CCL3, on the adhesion of CD4+ T cell subsets to human brain microvessel endothelial cells (HBMEC). Chemokines added to the lower compartment of a two-chamber chemotaxis system under confluent resting or cytokine-activated HBMEC, diffused through the culture substrate and bound to the basal surface of HBMEC. The low rate of adhesion of naïve, resting and memory CD4+ T cells to resting HBMEC was significantly upregulated following treatment of HBMEC with TNF-α and IFN-γ. Recently activated CD4+ T cells readily adhered to resting monolayers. Concentration gradients of CCL2 upregulated the adhesion of activated CD4+ T cells to cytokine treated but not resting HBMEC. The presence of CCL3 in the lower chamber increased the adhesion of memory T cells to both unstimulated and cytokine-treated HBMEC. These findings emphasize the importance of brain endothelial cell activation and the role of CCL2 and CCL3 in regulating the adhesion of CD4+ T cell subsets to BBB endothelium, thus contributing to the specificity of immune responses in MS.

Real-time analysis of integrin-dependent transendothelial migration and integrin-independent interstitial motility of leukocytes

The role of integrins in leukocyte migration across endothelial barriers is widely accepted. In contrast, the contribution of integrins to interstitial motility of leukocytes is still elusive. Chemokine binding to G-protein-coupled receptors expressed on the surface of leukocytes plays key roles in both of these processes by directly activating integrin conformations favorable for ligand binding and integrin microclustering. Chemokines can also serve as weak adhesive ligands and potent inducers of actin cytoskeleton remodeling. Real-time assays utilizing live imaging microscopy have been implemented to dissect these versatile roles of chemokines in different leukocyte migration processes. Here, we review several in vitro assays useful for exploring the contribution of chemokine signals and shear forces to integrin activation and function during various stages of leukocyte transendothelial migration. In addition, we describe a new assay that assesses the contribution of chemokines to integrin-independent interstitial leukocyte motility. These assays can also follow the outcome of specific genetic or biochemical manipulations of either the leukocyte or the endothelial barrier on distinct migratory steps. Following fixation, subcellular changes in the distribution of integrin subsets and of specific integrin-associated adaptors can be further dissected by immunofluorescence tools and by ultrastructural electron microscopic analysis.

RANTES/CCL5 and risk for coronary events: results from the MONICA/KORA Augsburg case-cohort, Athero-Express and CARDIoGRAM studies

BACKGROUND

The chemokine RANTES (regulated on activation, normal T-cell expressed and secreted)/CCL5 is involved in the pathogenesis of cardiovascular disease in mice, whereas less is known in humans. We hypothesised that its relevance for atherosclerosis should be reflected by associations between CCL5 gene variants, RANTES serum concentrations and protein levels in atherosclerotic plaques and risk for coronary events.

METHODS AND FINDINGS

We conducted a case-cohort study within the population-based MONICA/KORA Augsburg studies. Baseline RANTES serum levels were measured in 363 individuals with incident coronary events and 1,908 non-cases (mean follow-up: 10.2±4.8 years). Cox proportional hazard models adjusting for age, sex, body mass index, metabolic factors and lifestyle factors revealed no significant association between RANTES and incident coronary events (HR [95% CI] for increasing RANTES tertiles 1.0, 1.03 [0.75-1.42] and 1.11 [0.81-1.54]). None of six CCL5 single nucleotide polymorphisms and no common haplotype showed significant associations with coronary events. Also in the CARDIoGRAM study (>22,000 cases, >60,000 controls), none of these CCL5 SNPs was significantly associated with coronary artery disease. In the prospective Athero-Express biobank study, RANTES plaque levels were measured in 606 atherosclerotic lesions from patients who underwent carotid endarterectomy. RANTES content in atherosclerotic plaques was positively associated with macrophage infiltration and inversely associated with plaque calcification. However, there was no significant association between RANTES content in plaques and risk for coronary events (mean follow-up 2.8±0.8 years).

CONCLUSIONS

High RANTES plaque levels were associated with an unstable plaque phenotype. However, the absence of associations between (i) RANTES serum levels, (ii) CCL5 genotypes and (iii) RANTES content in carotid plaques and either coronary artery disease or incident coronary events in our cohorts suggests that RANTES may not be a novel coronary risk biomarker. However, the potential relevance of RANTES levels in platelet-poor plasma needs to be investigated in further studies.

Quantification of transendothelial migration using three-dimensional confocal microscopy

Migration of cells across endothelial barriers, termed transendothelial migration (TEM), is an important cellular process that underpins the pathology of many disease states including chronic inflammation and cancer metastasis. While this process can be modeled in vitro using cultured cells, many model systems are unable to provide detailed visual information of cell morphologies and distribution of proteins such as junctional markers, as well as quantitative data on the rate of TEM. Improvements in imaging techniques have made microscopy-based assays an invaluable tool for studying this type of detailed cell movement in physiological processes. In this chapter, we describe a confocal microscopy-based method that can be used to assess TEM of both leukocytes and cancer cells across endothelial barriers in response to a chemotactic gradient, as well as providing information on their migration into a subendothelial extracellular matrix, designed to mimic that found in vivo.

Uterine leiomyoma is associated with a polymorphism in the interleukin 1-beta gene

PROBLEM

To investigate whether polymorphisms in the interleukin-1beta (IL-1beta) gene are associated with uterine leiomyoma.

METHOD OF STUDY

Case-control study in a collective of 131 patients and 280 controls. Genotyping of the IL-1beta-511 and IL-1beta-3954 polymorphism was performed by PCR amplification and subsequent RFLP analysis.

RESULTS

A significant difference in the allele frequencies of the IL-1beta-511 C<T polymorphism was found. Allele frequencies of the IL-1beta-511 C<T polymorphism were 70.6% (C allele) in the patient group and 57.1% in the control group [P < 0.0002; odds ratio (OR) 1.81; 95% confidence interval (CI): 1.32-2.47]. The genotype distributions showed also differences using a dominant genotype model (C/C vs. C/T+T/T; P < 0.0002; OR 2.73; 95% CI: 1.77-4.2). No difference was found in the IL-1beta-3954 polymorphism.

CONCLUSION

The IL-1beta-511 promoter polymorphism is related to an increased susceptibility to uterine leiomyoma, suggesting that this polymorphism does contribute to the development of this disease.

Lymphocyte recruitment and homing to the liver in primary biliary cirrhosis and primary sclerosing cholangitis

The mechanisms operating in lymphocyte recruitment and homing to liver are reviewed. A literature review was performed on primary biliary cirrhosis (PBC), progressive sclerosing cholangitis (PSC), and homing mechanisms; a total of 130 papers were selected for discussion. Available data suggest that in addition to a specific role for CCL25 in PSC, the CC chemokines CCL21 and CCL28 and the CXC chemokines CXCL9 and CXCL10 are involved in the recruitment of T lymphocytes into the portal tract in PBC and PSC. Once entering the liver, lymphocytes localize to bile duct and retain by the combinatorial or sequential action of CXCL12, CXCL16, CX3CL1, and CCL28 and possibly CXCL9 and CXCL10. The relative importance of these chemokines in the recruitment or the retention of lymphocytes around the bile ducts remains unclear. The available data remain limited but underscore the importance of recruitment and homing.

Chapter 14. Real-time in vitro assays for studying the role of chemokines in lymphocyte transendothelial migration under physiologic flow conditions

The mechanisms underlying leukocyte migration across endothelial barriers are still largely elusive. Integrin activation by chemokine signals is a key checkpoint in this process. Most of the current knowledge on transendothelial migration (TEM) of leukocytes has been derived from in vitro modified Boyden-chamber transfilter migration assays. In these assays, leukocyte migration toward chemokine gradients established across an endothelial barrier is measured under shear-free conditions. Consequently, these assays do not address the critical contribution of shear forces to dynamic integrin activation and redistribution at focal lymphocyte-endothelial contacts. Endothelial chemokines are displayed at high levels on blood vessel walls in vivo and play critical roles in both integrin activation and polarization of leukocytes on blood vessels, yet transwell assays do not assess the role of these chemokines in leukocyte TEM. To overcome these two drawbacks, several laboratories, including our group, developed assays based on in vitro live imaging microscopy to follow leukocyte migration across endothelial barriers that display defined compositions of integrin-stimulatory chemokines. These assays not only successfully simulate physiologic TEM processes but also enable the tracking and dissection of leukocyte adhesion, motility, and crossing of endothelial barriers in real time and under physiologic flow conditions. In addition, fluorescent tagging of membranes, adhesion molecules, and cytoskeletal regulatory elements on the endothelial barrier or the leukocyte can provide key spatial and temporal information on the mode of activity of these elements during distinct stages of leukocyte TEM. After fixation, subcellular changes in the redistribution of these key molecules can be further dissected by immunofluorescence tools and by ultrastructural analysis based on scanning and transmission electron microscopy.

Direct observations of the kinetics of migrating T cells suggest active retention by endothelial cells with continual bidirectional migration

The kinetics and regulatory mechanisms of T cell migration through the endothelium have not been fully defined. In experimental, filter-based assays in vitro, transmigration of lymphocytes takes hours, compared with minutes, in vivo. We cultured endothelial cell (EC) monolayers on filters, solid substrates, or collagen gels and treated them with TNF-α, IFN-γ, or both prior to analysis of lymphocyte migration in the presence or absence of flow. PBL, CD4+ cells, or CD8+ cells took many hours to migrate through EC-filter constructs for all cytokine treatments. However, direct microscopic observations of EC filters, which had been mounted in a flow chamber, showed that PBL crossed the endothelial monolayer in minutes and were highly motile in the subendothelial space. Migration through EC was also observed on clear plastic, with or without flow. After a brief settling without flow, PBL and isolated CD3+ or CD4+ cells crossed EC in minutes, but the numbers of migrated cells varied little with time. Close observation revealed that lymphocytes migrated back and forth continuously across endothelium. Under flow, migration kinetics and the proportions migrating back and forth were altered little. On collagen gels, PBL again crossed EC in minutes and migrated back and forth but showed little penetration of the gel over hours. In contrast, neutrophils migrated efficiently through EC and into gels. These observations suggest a novel model for lymphoid migration in which EC support migration but retain lymphocytes (as opposed to neutrophils), and additional signal(s) are required for onward migration.

Enhanced T cell transmigration across the murine liver sinusoidal endothelium is mediated by transcytosis and surface presentation of chemokines

Transmigration through the liver endothelium is a prerequisite for the homeostatic balance of intrahepatic T cells and a key regulator of inflammatory processes within the liver. Extravasation into the liver parenchyma is regulated by the distinct expression patterns of adhesion molecules and chemokines and their receptors on the lymphocyte and endothelial cell surface. In the present study, we investigated whether liver sinusoidal endothelial cells (LSEC) inhibit or support the chemokine-driven transmigration and differentially influence the transmigration of pro-inflammatory or anti-inflammatory CD4(+) T cells, indicating a mechanism of hepatic immunoregulation. Finally, the results shed light on the molecular mechanisms by which LSEC modulate chemokine-dependent transmigration. LSEC significantly enhanced the chemotactic effect of CXC-motif chemokine ligand 12 (CXCL12) and CXCL9, but not of CXCL16 or CCL20, on naive and memory CD4(+) T cells of a T helper 1, T helper 2, or interleukin-10-producing phenotype. In contrast, brain and lymphatic endothelioma cells and ex vivo isolated lung endothelia inhibited chemokine-driven transmigration. As for the molecular mechanisms, chemokine-induced activation of LSEC was excluded by blockage of G(i)-protein-coupled signaling and the use of knockout mice. After preincubation of CXCL12 to the basal side, LSEC took up CXCL12 and enhanced transmigration as efficiently as in the presence of the soluble chemokine. Blockage of transcytosis in LSEC significantly inhibited this effect, and this suggested that chemokines taken up from the basolateral side and presented on the luminal side of endothelial cells trigger T cell transmigration.

CONCLUSION

Our findings demonstrate a unique capacity of LSEC to present chemokines to circulating lymphocytes and highlight the importance of endothelial cells for the in vivo effects of chemokines. Chemokine presentation by LSEC could provide a future therapeutic target for inhibiting lymphocyte immigration and suppressing hepatic inflammation.

Interferon-gamma limits Th1 lymphocyte adhesion to inflamed endothelium: a nitric oxide regulatory feedback mechanism

CD4(+) T helper (Th1 and Th2) cell localization to a site of inflammation is important for the development, maintenance and regulation of an immune response. The factors that regulate Th1 and Th2 cell recruitment into tissue are not fully understood. The aim of the present study was to examine the effect of different cytokine microenvironments on the recruitment of Th1 and Th2 lymphocytes into tissue. Fluorescently labelled Th1 or Th2 lymphocyte-endothelial interactions were observed via intravital microscopy of the cytokine-treated cremaster muscle. Our results show that TNF-alpha alone is sufficient to maximally recruit Th1 cells. Surprisingly, treatment with TNF-alpha + IFN-gamma significantly decreased Th1 adhesion and emigration in comparison to TNF-alpha treatment alone. The decreased adhesion of Th1 cells in response to TNF-alpha + IFN-gamma reflected a decreased ability to bind to ICAM-1 and was iNOS-dependent. This phenomenon was not observed with Th2 cells. These results suggest that IFN-gamma may play a key immunomodulatory role in the recruitment of different T lymphocyte subsets. Indeed, blockade of IFN-gamma or iNOS function during the Th1-mediated contact hypersensitivity response resulted in an acceleration and exacerbation of the late-phase inflammatory response.

Immunotherapy of patients with hormone-refractory prostate carcinoma pre-treated with interferon-gamma and vaccinated with autologous PSA-peptide loaded dendritic cells--a pilot study

PURPOSE

We conducted a pilot trial to assess the feasibility and tolerability of a prime/boost vaccine strategy using interferon-gamma (IFN-gamma) and autologous dendritic cells (DCs) pulsed with HLA-A2-specific prostate-specific antigen (PSA) peptides (PSA-1 [141-150]; PSA-2 [146-156]; PSA-3 [154-163]) for the treatment of 12 patients with hormone refractory prostate carcinoma.

PATIENTS AND METHODS

All patients were vaccinated four times with intracutaneously injected PSA-peptide loaded DCs after subcutaneous administration of IFN-gamma 2 hr before DC administration (50 microg/m(2) body surface). Objectives were safety, clinical benefit, clinical and biochemical response, quality of life, and immunological parameters.

RESULTS

The vaccination was well tolerated without any vaccination-associated adverse events. One partial and one mixed responder were identified, four patients showed stable diseases. Two patients had a decrease and four a slow-down velocity slope in the PSA serum level. All responders showed a positive DTH-response, but only two a slight increase in PSA-peptide specific T-lymphocytes.

CONCLUSION

The immunotherapy with IFN-gamma and PSA-peptide loaded DCs was feasible and well tolerated. The observed responses imply a potential antitumor activity.

Up-regulation of functional CXCR4 expression on human lymphocytes in sepsis

OBJECTIVE

Lymphocyte dysfunction has been documented in sepsis, and evidence suggests that lymphocyte infiltration contributes to tissue injury. The purpose of this study was to examine chemokine receptor expression and function in lymphocytes from septic patients and healthy donors.

DESIGN

Observational study of septic patients and laboratory investigation of normal controls.

SETTING

Tertiary care intensive care unit.

PATIENTS AND SUBJECTS

Nine critically ill patients fulfilling criteria for the systemic inflammatory response syndrome and with a Sepsis Score of >/=3 were included in this study. Lymphocytes were also obtained from healthy volunteers.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The total number of circulating leukocytes in septic patients was markedly increased; however, lymphocyte counts were decreased. Chemokine receptor expression on lymphocytes was examined by flow cytometry. CXCR4 expression on lymphocytes from septic patients was increased whereas CCR5 was decreased and CCR7 was unchanged. Lipopolysaccharide stimulation of normal lymphocytes increased CXCR4 expression but decreased CCR5 and did not change CCR7 expression. This lipopolysaccharide-stimulated CXCR4 expression required 20 hrs of stimulation and was accompanied by increased messenger RNA. Lymphocytes from septic patients or after lipopolysaccharide treatment demonstrated enhanced actin polymerization and migration in response to CXCL12. Taken together, sepsis and lipopolysaccharide up-regulated CXCR4 expression and enhanced lymphocyte activation and migration in response to CXCL12.

CONCLUSIONS

Blocking CXCR4 and CXCL12 function may provide a novel therapeutic method for controlling systemic inflammation and tissue injury in sepsis.

Negative association between circulating total homocysteine and proinflammatory chemokines MCP-1 and RANTES in prepubertal lean, but not in obese, children

This study investigated in prepubertal obese children (POC), compared with prepubertal lean children (PLC), a possible relation among plasma total homocysteine (tHcy)-an independent risk factor for future atherosclerosis-and MCP-1 and RANTES, two circulating chemokines inducing leukocyte transendothelial migration (TEM), implicated in the initial stages of the inflammatory part of the atherosclerotic process. Seventy-two POC were evaluated for circulating tHcy, MCP-1, and RANTES, and compared with 42 healthy PLC. The mean adjusted (for age, sex as well as log10total insulin, vitB12, folate, total cholesterol, HDL cholesterol, log10triglycerides, and log10glucose levels) differences in tHcy, MCP-1, and RANTES levels between PLC and POC were all significant [1.16 nmol/mL (P = 0.03), 26.6 pg/mL (P = 0.02), and 52.9 pg/mL (P = 0.03), respectively]. In PLC, but not in POC, tHcy levels were negatively associated with both circulating MCP-1 (B = -1.68, P = 0.007) and RANTES (B = -1.16, P = 0.01) after adjusting for age, sex, BMI, as well as log10total insulin, vitB12, folate, total cholesterol, HDL cholesterol, log10triglycerides, and log10glucose levels. In conclusion, in POC there is a lack, in contrast to PLC, of a possibly autoregulatory, negative association of elevated tHcy levels to increased MCP-1 and RANTES levels. This could contribute to future, homocysteine-induced atherosclerosis.

Localization of the α-chemokine SDF-1 and its receptor CXCR4 in idiopathic inflammatory myopathies

We studied the distribution of stromal cell-derived factor 1 isoforms alpha and beta, and their receptor CXCR4, in polymyositis, sporadic inclusion body myositis and dermatomyositis using in situ hybridization, immunohistochemistry, immunofluorescence and Western blotting. In control muscle, polymyositis and sporadic inclusion body myositis, stromal cell-derived factor-1alpha expression was noted in muscle fibers, while stromal cell-derived factor-1beta and CXCR4 were predominantly localized to capillaries and arterioles. In dermatomyositis, stromal cell-derived factor-1beta immunoreactivity of blood vessels was focally increased. The vast majority of inflammatory cells in idiopathic inflammatory myopathies were CXCR4 positive. A subset of helper T-cells and macrophages expressed stromal cell-derived factor-1alpha, while only rare inflammatory cells expressed stromal cell-derived factor-1beta. A significant increase of stromal cell-derived factor-1alpha and CXCR4 was observed in protein extracts of idiopathic inflammatory myopathies in comparison with normal controls. The abundance of both CXCR4 and its ligand stromal cell-derived factor-1 implicates their interaction in the pathogenesis of idiopathic inflammatory myopathies and identifies these proteins as possible targets for selective immune therapy.

CD40-mediated immune-nonimmune cell interactions induce mucosal fibroblast chemokines leading to T-cell transmigration

BACKGROUND AND AIMS

The CD40 pathway is a key mediator of inflammation and autoimmunity. We investigated cell adhesion molecule (CAM) up-regulation and chemokine production by CD40-positive human intestinal fibroblasts (HIF) and microvascular endothelial cells (HIMEC) induced by CD40 ligand (CD40L)-positive T cells and soluble CD40L and their effect on T-cell adhesion and transmigration.

METHODS

Expression of CD40, CD40L, and CAM was assessed by immunohistochemistry, confocal microscopy and flow cytometric analysis, and chemokine production using enzyme-linked immunosorbent assay. Calcein-labeled T cells were used to assay HIF adhesion and Transwell HIMEC transmigration.

RESULTS

Ligation of CD40-positive HIF and HIMEC by CD40L-positive T cells or soluble CD40L induced up-regulation of CAM expression as well as interleukin-8 and RANTES production. The specificity of these responses was shown by inhibition with a CD40L blocking antibody and by CD40 signaling-dependent p38 mitogen-activated protein kinase phosphorylation. On CD40 ligation, HIF increased their T-cell binding capacity and generated chemoattractants able to induce T-cell migration through HIMEC monolayers.

CONCLUSIONS

Activation of the CD40/CD40L system in the gut mucosa may trigger a self-sustaining loop of immune-nonimmune cell interactions leading to an antigen-independent influx of T cells that contributes to chronic inflammation.

In vivo expression of interleukin-8, and regulated on activation, normal, T-cell expressed, and secreted, by human germinal centre B lymphocytes

T-cell homing within germinal centres (GCs) is required for humoral B-cell responses. However, the mechanisms implicated in the recruitment of T cells into the GC are not completely understood. Here we show, by immunohistology, and Northern and Western blots, that in vivo human GC B lymphocytes can express CxC and CC chemokines. Moreover, B-cell subset-specific experiments reveal that interleukin (IL)-8 and regulated on activation, normal, T-cell expressed, and secreted (RANTES) are predominantly expressed by GC centroblast and centrocytes, suggesting that chemokine expression is essential at stages in which B-lymphocytes engage in active antigen-dependent interactions with T lymphocytes. In keeping with this hypothesis, we show that the T cells recruited into the GC correlatively express the receptors for IL-8 and RANTES. We propose that chemokine expression is a key B-cell function that facilitates T-lymphocyte recruitment into the GCs and supports cognate B-cell : T-cell encounters. Moreover, our data are consistent with the impaired homing of T cells to secondary lymphoid organs in mice that are either deficient in CC and CxC chemokines or their receptors.

Mast cell-derived tumor necrosis factor induces hypertrophy of draining lymph nodes during infection

Palpable swelling of regional lymph nodes is a common sequela of microbial infections but the mechanism responsible for the sequestration and subsequent coordination of lymphocyte responses within these dynamic structures remains poorly understood. Here we show that draining lymph nodes of mast cell-deficient mice did not demonstrate swelling after intradermal bacterial challenge. Testing of individual mast cell-derived products in this model indicated that tumor necrosis factor was the main mediator of nodal hypertrophy, whereas tryptase and histamine had no effect. After peripheral mast cell activation, both tumor necrosis factor concentrations and the recruitment of circulating T cells were increased within draining nodes. These results show a critical function for peripheral mast cell-derived tumor necrosis factor in regulating the hypertrophy of draining lymph nodes during infection.

The relative activity of CXCR3 and CCR5 ligands in T lymphocyte migration: concordant and disparate activities in vitro and in vivo

In chronic inflammatory reactions such as rheumatoid arthritis and multiple sclerosis, T cells in the inflamed tissue express the chemokine receptors CXCR3 and CCR5, and the chemokine ligands (CCL) of these receptors are present in the inflammatory lesions. However, the contribution of these chemokines to T cell recruitment to sites of inflammation is unclear. In addition, the relative roles of the chemokines that bind CXCR3 (CXCL9, CXCL10, CXCL11) and CCR5 (CCL3, CCL4, CCL5) in this process are unknown. The in vitro chemotaxis and in vivo migration of antigen-activated T lymphoblasts and unactivated spleen T cells to chemokines were examined. T lymphoblasts migrated in vitro to CXCR3 ligands with a relative potency of CXCL10 > CXCL11 > CXCL9, but these cells demonstrated much less chemotaxis to the CCR5 ligands. In vivo, T lymphocytes were recruited in large numbers with rapid kinetics to skin sites injected with CXCL10 and CCL5 and less to CCL3, CCL4, CXCL9, and CXCL11. The combination of CCL5 with CXCL10 but not the other chemokines markedly increased recruitment. Coinjection of interferon-gamma, tumor necrosis factor alpha, and interleukin-1alpha to up-regulate endothelial cell adhesion molecule expression with CXCL10 or CCL5 induced an additive increase in lymphoblast migration. Thus, CXCR3 ligands are more chemotactic than CCR5 ligands in vitro; however, in vivo, CXCL10 and CCL5 have comparable T cell-recruiting activities to cutaneous sites and are more potent than the other CXCR3 and CCR5 chemokines. Therefore, in vitro chemotaxis induced by these chemokines is not necessarily predictive of their in vivo lymphocyte-recruiting activity.

A stochastic view of lymphocyte motility and trafficking within the lymph node

Two-photon microscopy is providing literal insight into the cellular dynamics of lymphoid organs and, guided by analysis of three-dimensional images, into mechanisms that underlie cell migration and antigen recognition in vivo. This review describes lymphocyte motility and antigen recognition in the native tissue environment and compares these results with a much more extensive literature on lymphocyte motility, signaling, and chemotaxis in vitro. We discuss the in vitro literature on dynamic aspects of lymphocyte motility, chemotaxis, and the response to antigen and present the view that random migration of lymphocytes may drive a stochastic mechanism of antigen recognition in lymphoid organs, rather than being guided by chemotaxis.

Identification of tissue transglutaminase as a novel molecule involved in human CD8+ T cell transendothelial migration

During inflammation, T lymphocytes migrate out of the blood across the vascular endothelium in a multistep process. The receptors mediating T cell adhesion to endothelium are well characterized; however, the molecules involved in T cell transendothelial migration (TEM) subsequent to lymphocyte adhesion to the endothelium are less clear. To identify receptors mediating TEM, mAbs were produced against human blood T cells adhering to IFN-gamma-activated HUVEC in mice and tested for inhibition of lymphocyte TEM across cytokine-activated HUVEC. Most of the mAbs were against beta(1) and beta(2) integrins, but one mAb, 6B9, significantly inhibited T cell TEM across IFN-gamma, TNF-alpha, and IFN-gamma plus TNF-alpha-stimulated HUVEC, and did not react with an integrin. 6B9 mAb did not inhibit T cell adhesion to HUVEC, suggesting that 6B9 blocked a novel pathway in T cell TEM. The 6B9 Ag was 80 kDa on SDS-PAGE, and was expressed by both blood leukocytes and HUVEC. Immunoaffinity purification and mass spectrometry identified this Ag as tissue transglutaminase (tTG), a molecule not known to mediate T cell TEM. Treatment of HUVEC with 6B9 was more effective than treatment of T cells. 6B9 blockade selectively inhibited CD4(-), but not CD4(+), T cell TEM, suggesting a role for tTG in recruitment of CD8(+) T lymphocytes. Thus, 6B9 is a new blocking mAb to human tTG, which demonstrates that tTG may have a novel role in mediating CD8(+) T cell migration across cytokine-activated endothelium and infiltration of tissues during inflammation.

L-selectin stimulation enhances functional expression of surface CXCR4 in lymphocytes: implications for cellular activation during adhesion and migration

L-selectin mediates leukocyte tethering and rolling, the first step in a sequential process of leukocyte adhesion and migration. Additionally, L-selectin has important signaling roles perhaps contributing to leukocyte activation and integrin-mediated adhesion. Because chemokines are critically involved in leukocyte activation, we questioned whether L-selectin signaling affects chemokine receptor expression and function. We observed that whereas only 5% to 15% of freshly isolated lymphocytes expressed CXCR4 on the cell surface, intracellular CXCR4 was detectable in all cells. Engagement of L-selectin by antibody cross-linking or the L-selectin ligands fucoidan or sulfatide mobilized intracellular CXCR4 to significantly increase surface CXCR4 expression but did not affect CCR5, CCR7, or beta2-integrin expression. L-selectin stimulation also inhibited stromal-derived factor 1 (SDF-1)-induced CXCR4 internalization. The combined effects of L-selectin on CXCR4 trafficking are likely important in markedly enhancing cell activation by SDF-1. Blockade of SDF-1-induced CXCR4 internalization resulted in enhanced actin polymerization on subsequent exposure to SDF-1. Physiologically more important, L-selectin stimulation increased SDF-1-induced lymphocyte adhesion and transendothelial migration, which were inhibited by anti-leukocyte function-associated antigen 1 antibodies, tyrosine kinase inhibitors, and pertussis toxin. To further corroborate the additive stimulating effects, L-selectin signaling and SDF-1 increased beta2-integrin activation. Taken together, L-selectin-mediated signals specifically enhance CXCR4 expression and function, suggesting a novel mechanism for the modulation of lymphocyte activation during cell adhesion and transmigration.

A real time in vitro assay for studying leukocyte transendothelial migration under physiological flow conditions

The mechanisms underlying leukocyte migration across endothelial barriers are largely elusive. Most of the current knowledge on transendothelial migration (TEM) of leukocytes has been derived from in vitro modified Boyden chamber transfilter migration assays. In these assays, leukocyte migration towards chemokine gradients constructed across the endothelial barrier is measured under shear-free conditions. These assays do not incorporate the contribution of shear flow to leukocyte adherence and migration across the endothelial barrier. Furthermore, transfilter assays do not reconstitute the physiological distribution of endothelial chemokines shown to be displayed in vivo at high levels on vessel walls. To overcome these two drawbacks, we have recently developed a novel in vitro assay to follow real time leukocyte migration across endothelial barriers under physiological flow conditions. Using this assay, we have found that apically displayed endothelial chemokines could trigger robust lymphocyte TEM through signaling to lymphocyte-expressed G-protein coupled receptors. This migration required continuous exposure of lymphocytes, adherent to the endothelial barrier, to fluid shear, but did not require a chemotactic gradient across the barrier. In the present review, we describe this new flow-based migration assay and discuss future applications for investigating TEM processes of different types of leukocytes across distinct endothelial barriers.

An association between the acute phase response and patterns of antigen induced T cell proliferation in juvenile idiopathic arthritis

The aim of this research was to determine whether all memory T cells have the same propensity to migrate to the joint in patients with juvenile idiopathic arthritis. Paired synovial fluid and peripheral blood mononuclear cell proliferative responses to a panel of antigens were measured and the results correlated with a detailed set of laboratory and clinical data from 39 patients with juvenile idiopathic arthritis. Two distinct patterns of proliferative response were found in the majority of patients: a diverse pattern, in which synovial fluid responses were greater than peripheral blood responses for all antigens tested; and a restricted pattern, in which peripheral blood responses to some antigens were more vigorous than those in the synovial fluid compartment. The diverse pattern was generally found in patients with a high acute phase response, whereas patients without elevated acute phase proteins were more likely to demonstrate a restricted pattern. We propose that an association between the synovial fluid T cell repertoire and the acute phase response suggests that proinflammatory cytokines may influence recruitment of memory T cells to an inflammatory site, independent of their antigen specificity. Additionally, increased responses to enteric bacteria and the presence of alphaEbeta7 T cells in synovial fluid may reflect accumulation of gut associated T cells in the synovial compartment, even in the absence of an elevated acute phase response. This is the first report of an association between the acute phase response and the T cell population recruited to an inflammatory site.

IFN-gamma-inducible T cell alpha chemoattractant is a potent stimulator of normal human blood T lymphocyte transendothelial migration: differential regulation by IFN-gamma and TNF-alpha

Previous studies have shown that the CXC chemokine, IFN-gamma-inducible T cell alpha chemoattractant (I-TAC), was chemotactic for IL-2-activated human T lymphocytes, which express abundant CXCR3. However, because most memory T lymphocytes are also CXCR3(+), the ability of I-TAC to promote the migration of normal human blood T cells across HUVEC monolayers in Transwell chambers was examined. I-TAC induced a marked (4- to 6-fold) increase in transendothelial migration (TEM) of T cells across unstimulated HUVEC from 5.6 to 28% of input T cells and was substantially more active than IFN-gamma-inducible protein-10, another CXCR3 ligand. I-TAC significantly enhanced TEM of T cells across TNF-alpha, but not across IFN-gamma or IFN-gamma plus TNF-alpha-activated HUVEC. IFN-gamma or IFN-gamma plus TNF-alpha-activated HUVEC produced substantial amounts of I-TAC, in contrast to TNF-alpha-treated EC. Both CD4(+) and CD8(+) T cells migrated in response to I-TAC to a similar extent, while memory T cells migrated several fold better than naive T cells. Blockade of LFA-1 strongly inhibited I-TAC-induced T cell TEM across unstimulated HUVEC, and approximately 50-60% of the TEM across cytokine-activated HUVEC. However, blocking both LFA-1 and very late Ag-4 abolished I-TAC induced T cell TEM. In vivo significant levels of I-TAC were detected in arthritic synovial fluid. Thus, I-TAC is one of the most potent chemoattractants of normal human blood CD4 and CD8 T cell TEM and is likely a major mediator of blood memory T lymphocyte migration to inflammation.

Radiation pneumonitis and early circulatory cytokine markers

Radiation pneumonitis is a distinct clinical entity that differs from other pulmonary symptoms such as allergic pneumonitis, chemical pneumonitis, or pneumonia by various infectious agents. Recent research has supported the mechanism of cellular interaction between lung parenchymal cells and circulating immune cells mediated through a variety of cytokines including proinflammatory cytokines, chemokines, adhesion molecules, and profibrotic cytokines. Identifying reliable biomarkers for radiation pneumonitis will allow us to identify individuals at risk for pneumonitis before or during the early stage of therapy. Prospective blood sampling, scoring of respiratory symptoms, and chest imaging were conducted for patients receiving thoracic radiotherapy for malignancy. Serial plasma specimens were analyzed for circulating cytokine changes before, during, and up to 12 weeks after radiation. Radiation pneumonitis was diagnosed using National Cancer Institute (NCI) common toxicity criteria. Cytokine analysis was assayed for interleukin 1alpha (IL-1alpha), interleukin 6 (IL-6), monocyte chemotactic protein 1 (MCP-1), E-selectin, L-selectin, transforming growth factor beta1 (TGF-beta1), and basic fibroblast growth factor (bFGF) using enzyme linked immmunosorbant assay (ELISA). Twenty-four patients had clinical follow-up longer than 12 months after radiotherapy. Thirteen had symptomatic pneumonitis (NCI grade 2). The peak incidence of symptoms was between 6 and 13 weeks after radiotherapy. Six patients had only radiographic infiltrates (NCI grade 1). Five patients did not have clinical or radiographic pneumonitis. Both IL-1alpha and IL-6 levels were significantly higher before, during, and after radiotherapy for those who had pneumonitis. The pattern of changes of MCP-1, E-selectin, L-selectin, TGF-beta1, and bFGF varied, but none of these cytokines correlated with radiation pneumonitis. Analysis of a panel of circulating cytokines with different putative functions in radiation pulmonary injury identified IL-1alpha and IL-6 as early circulating cytokine markers for radiation pneumonitis.

Expression of CD3 and CD11b antigens on blood and mammary gland leukocytes and bacterial survival in milk of cows with experimentally induced Staphylococcus aureus mastitis

OBJECTIVES

To differentiate early (1 to 8 days) from late (9 to 14 days) inflammatory phases and assess relationships between leukocyte phenotype and bacterial recovery in cows with Staphylococcus aureus-induced mastitis.

ANIMALS

10 first-lactation Holstein cows.

PROCEDURE

Blood and milk samples were collected from 4 or 6 cows before and after intramammary infusion of sterile broth or S. aureus, respectively. Flow cytometric expression of CD3 and CD11b antigens on blood and milk leukocytes, leukocyte differential counts, bacterial counts in milk, and somatic cell counts were determined longitudinally.

RESULTS

Density of CD3 molecules decreased on blood lymphocytes and increased on milk lymphocytes after infusion of bacteria. Density of CD11b molecules on lymphocytes and phagocytes and percentage of CD11b+ lymphocytes in milk increased significantly after infusion; maximum values were achieved during the early inflammatory phase. Density of CD3 and CD11b molecules on milk lymphocytes and macrophages, respectively, 1 day after inoculation were negatively correlated with bacterial recovery on day 1 and days 9 to 14, respectively. Density of CD11b molecules on milk macrophages and the ratios of phagocyte to lymphocyte percentages and polymorphonuclear cell to macrophage percentages in milk differentiated the early from the late inflammatory phase.

CONCLUSIONS AND CLINICAL RELEVANCE

Activation of bovine mammary gland macrophages and T cells in response to intramammary infusion of S. aureus was associated with an inability to culture this bacterium from milk. Identification of specific inflammatory phases of S. aureus-induced mastitis in cows may allow for the design of more efficacious treatment and control programs.

Shear forces promote lymphocyte migration across vascular endothelium bearing apical chemokines

Leukocyte transendothelial migration (TEM) is thought to be a chemotactic process controlled by chemokine gradients across the endothelium. Using cytokine-activated human umbilical vascular endothelial cells (HUVECs) as a model of inflamed endothelium, we have shown that apical endothelial chemokines can trigger robust peripheral blood lymphocyte (PBL) migration across endothelial cells. Lymphocyte TEM was promoted by physiological shear stress applied continuously to migrating lymphocytes. Lymphocyte integrins, intact actin cytoskeleton and G(i) protein-mediated chemokine signaling, but not a chemotactic gradient, were mandatory for TEM. PBL TEM did not require intracellular free calcium or intact phosphatidyl inositol kinase activity in migrating lymphocytes. Thus, lymphocyte TEM is promoted by fluid shear-induced mechanical signals coupled to G(i) protein signals at apical endothelial zones.

Phenotypic characteristics of human monocytes undergoing transendothelial migration

In our study we characterised the immunophenotype of monocytes that migrated through an endothelial cell (EC) monolayer in vitro. We found that monocyte migration led to an enhanced expression of CD11a, CD33, CD45RO, CD54 [intercellular cell-adhesion molecule (ICAM)-1] and human leucocyte antigen-DR. The most striking increase was observed for ICAM-1 when ECs were activated with tumour necrosis factor-alpha and interleukin-1alpha. The results of our study indicate the following: (1) there is a characteristic immunophenotype on the surface of monocytes after transendothelial migration; (2) this phenotype seems to be induced by interactions between monocytes and ECs; and (3) this change is enhanced by the pretreatment of ECs with cytokines. Taken together, the results suggest that local cytokine production activating ECs is sufficient to enhance monocyte migration and that this, in turn, can induce changes consistent with an activated phenotype known to be interactive between antigen-presenting cells and T cells. These results have implications for our pathogenetic insights into rheumatoid arthritis.