Lymphocyte homing and leukocyte rolling and migration are impaired in L-selectin-deficient mice

L-Selectin/CD62L is a Key Driver of Non-Alcoholic Steatohepatitis in Mice and Men

CD62L (L-Selectin) dependent lymphocyte infiltration is known to induce inflammatory bowel disease (IBD), while its function in the liver, especially in non-alcoholic steatohepatitis (NASH), remains unclear. We here investigated the functional role of CD62L in NASH in humans as well as in two mouse models of steatohepatitis. Hepatic expression of a soluble form of CD62L (sCD62L) was measured in patients with steatosis and NASH. Furthermore, CD62L^−/− mice were fed with a methionine and choline deficient (MCD) diet for 4 weeks or with a high fat diet (HFD) for 24 weeks. Patients with NASH displayed increased serum levels of sCD62L. Hepatic CD62L expression was higher in patients with steatosis and increased dramatically in NASH patients. Interestingly, compared to wild type (WT) mice, MCD and HFD-treated CD62L^−/− mice were protected from diet-induced steatohepatitis. This was reflected by less fat accumulation in hepatocytes and a dampened manifestation of the metabolic syndrome with an improved insulin resistance and decreased cholesterol and triglyceride levels. Consistent with ameliorated disease, CD62L^−/− animals exhibited an enhanced hepatic infiltration of Treg cells and a strong activation of an anti-oxidative stress response. Those changes finally resulted in less fibrosis in CD62L^−/− mice. Additionally, this effect could be reproduced in a therapeutic setting by administrating an anti-CD62L blocking antibody. CD62L expression in humans and mice correlates with disease activity of steatohepatitis. CD62L knockout and anti-CD62L-treated mice are protected from diet-induced steatohepatitis suggesting that CD62L is a promising target for therapeutic interventions in NASH.

The role of myeloid-derived suppressor cells in the pathogenesis of rheumatoid arthritis; anti- or pro-inflammatory cells?

Myeloid-derived suppressor cells (MDSCs) are a heterogeneous group of the immature myeloid cells that are derived from the myeloid progenitors with immunosuppressive functions. MDSCs are accumulated in the inflammatory sites during some autoimmune disorders, such as rheumatoid arthritis (RA) and can be an important factor in the pathogenesis of these diseases. Some research has shown the anti-inflammatory role of MDSCs during the RA progression and supports the hypothesis that MDSCs can be a potential treatment option for autoimmunity with their immunosuppressive activity. In contrast, some papers have reported the opposite effects of MDSCs, and support the hypothesis that MDSCs have a pro-inflammatory role in autoimmune disease. MDSCs functions in RA have not been fully understood, and some controversies, as well as many unanswered questions, remain. Although the two well-known subgroups of MDSCs, M-MDSC, and PMN-MDSC, seem to have different suppressive functions and regulate the immune system responses in a different manner; some studies have shown these cells are converted to each other and even to other cells under different pathological conditions. This review summarises some of the latest papers with respect to the MDSCs functions and discusses the relationship between MDSCs and inflammation in the context of rheumatoid arthritis.

ADAM17 protects against elastase-induced emphysema by suppressing CD62L+ leukocyte infiltration in mice

Pulmonary emphysema is a major manifestation of chronic obstructive pulmonary disease and is associated with chronic pulmonary inflammation caused by cigarette smoking, with contributions from immune cells such as neutrophils, macrophages, and lymphocytes. Although matrix metalloproteinases are well known to contribute to emphysema progression, the role of a disintegrin and metalloproteinase (ADAM) family proteins, other major metalloproteinases, in disease pathogenesis is largely unknown. ADAM17 is a major sheddase that cleaves various cell surface proteins, including CD62L, an adhesion molecule that plays a critical role in promoting the migration of immune cells to the site of inflammation. In the present study, we aimed to investigate the potential role of ADAM17 and CD62L in the development of elastase-induced emphysema. Control and Adam17^flox/flox/Mx1-Cre (Adam17^ΔMx1) mice (8-10 wk old) were intratracheally injected with 5 units of porcine pancreas elastase and monitored for 35 days after injection. Lung alveolar destruction was evaluated by analyzing the mean linear intercepts of lung tissue specimens and by histopathological examination. Mean linear intercepts data indicated that the degree of elastase-induced emphysema was significantly more severe in Adam17^ΔMx1 mice. Furthermore, flow cytometry showed that CD62L⁺ neutrophil, CD62L⁺ macrophage, and CD62L⁺ B lymphocyte numbers were significantly increased in Adam17^ΔMx1 mice. Moreover, the pharmacological depletion of CD62L⁺ cells with a CD62L-neutralizing antibody ameliorated the extent of emphysema in Adam17^ΔMx1 mice. Collectively, these results suggest that ADAM17 possibly suppresses the progression of emphysema by proteolytically processing CD62L in immune cells and that ADAM17 and CD62L could be novel therapeutic targets for treating pulmonary emphysema.

Multimodal single-cell approaches shed light on T cell heterogeneity

Single-cell methods have revolutionized the study of T cell biology by enabling the identification and characterization of individual cells. This has led to a deeper understanding of T cell heterogeneity by generating functionally relevant measurements - like gene expression, surface markers, chromatin accessibility, T cell receptor sequences - in individual cells. While these methods are independently valuable, they can be augmented when applied jointly, either on separate cells from the same sample or on the same cells. Multimodal approaches are already being deployed to characterize T cells in diverse disease contexts and demonstrate the value of having multiple insights into a cell's function. But, these data sets pose new statistical challenges for integration and joint analysis.

Differences in Expression of Human Leukocyte Antigen Class II Subtypes and T Cell Subsets in Behçet's Disease with Arthritis

It has been reported Human Leukocyte Antigen (HLA) gene polymorphism is a risk factor for the development of Behçet’s disease (BD). In this study, the association of HLA class II subtypes HLA-DP, DQ, DR, and T cell subsets in BD patients with arthritis was evaluated. Frequencies of HLA-DP, DQ, DR positive cells, and T cell subsets in peripheral blood leukocytes (PBL) were measured by flow cytometric analysis in BD, and compared to rheumatoid arthritis as disease controls and healthy controls. Frequencies of HLA-DQ were significantly decreased in whole PBL and granulocytes of BD active patients as compared to healthy controls. In monocytes populations, proportions of HLA-DR positive cells were significantly increased in BD active patients as compared to healthy controls. Proportions of CD4+CCR7+ and CD8+CCR7+ cells were significantly higher in BD active patients than in BD inactive in whole PBL. Frequencies of CD4+CD62L- and CD8+CD62L- cells in lymphocytes were significantly decreased in active BD than those in inactive BD. There were also correlations between disease activity markers and T cell subsets. Our results revealed HLA-DP, DQ, and DR expressing cell frequencies and several T cell subsets were significantly correlated with BD arthritis symptoms.

Serine Phosphorylation of L-Selectin Regulates ERM Binding, Clustering, and Monocyte Protrusion in Transendothelial Migration

The migration of circulating leukocytes toward damaged tissue is absolutely fundamental to the inflammatory response, and transendothelial migration (TEM) describes the first cellular barrier that is breached in this process. Human CD14⁺ inflammatory monocytes express L-selectin, bestowing a non-canonical role in invasion during TEM. In vivo evidence supports a role for L-selectin in regulating TEM and chemotaxis, but the intracellular mechanism is poorly understood. The ezrin-radixin-moesin (ERM) proteins anchor transmembrane proteins to the cortical actin-based cytoskeleton and additionally act as signaling adaptors. During TEM, the L-selectin tail within transmigrating pseudopods interacts first with ezrin to transduce signals for protrusion, followed by moesin to drive ectodomain shedding of L-selectin to limit protrusion. Collectively, interaction of L-selectin with ezrin and moesin fine-tunes monocyte protrusive behavior in TEM. Using FLIM/FRET approaches, we show that ERM binding is absolutely required for outside-in L-selectin clustering. The cytoplasmic tail of human L-selectin contains two serine (S) residues at positions 364 and 367, and here we show that they play divergent roles in regulating ERM binding. Phospho-S364 blocks direct interaction with ERM, whereas molecular modeling suggests phospho-S367 likely drives desorption of the L-selectin tail from the inner leaflet of the plasma membrane to potentiate ERM binding. Serine-to-alanine mutagenesis of S367, but not S364, significantly reduced monocyte protrusive behavior in TEM under flow conditions. Our data propose a model whereby L-selectin tail desorption from the inner leaflet of the plasma membrane and ERM binding are two separable steps that collectively regulate protrusive behavior in TEM.

Mass Production of Highly Active NK Cells for Cancer Immunotherapy in a GMP Conform Perfusion Bioreactor

NK cells have emerged as promising candidates for cancer immunotherapy, especially due to their ability to fight circulating tumor cells thereby preventing metastases formation. Hence several studies have been performed to generate and expand highly cytotoxic NK cells ex vivo, e.g., by using specific cytokines to upregulate both their proliferation and surface expression of distinct activating receptors. Apart from an enhanced activity, application of NK cells as immunotherapeutic agent further requires sufficient cell numbers and a high purity. All these parameters depend on a variety of different factors including the starting material, additives like cytokines as well as the culture system. Here we analyzed PBMC-derived NK cells of five anonymized healthy donors expanded under specific conditions in an innovative perfusion bioreactor system with respect to their phenotype, IFNγ production, and cytotoxicity in vitro. Important features of the meander type bioreactors used here are a directed laminar flow of medium and control of relevant process parameters. Cells are cultivated under "steady state" conditions in perfusion mode. Our data demonstrate that expansion of CD3⁺ T cell depleted PBMCs in our standardized system generates massive amounts of highly pure (>85%) and potent anti-cancer active NK cells. These cells express a variety of important receptors driving NK cell recruitment, adhesion as well as activation. More specifically, they express the chemokine receptors CXCR3, CXCR4, and CCR7, the adhesion molecules L-selectin, LFA-1, and VLA-4, the activating receptors NKp30, NKp44, NKp46, NKG2D, DNAM1, and CD16 as well as the death ligands TRAIL and Fas-L. Moreover, the generated NK cells show a strong IFNγ expression upon cultivation with K562 tumor cells and demonstrate a high cytotoxicity toward leukemic as well as solid tumor cell lines in vitro. Altogether, these characteristics promise a high clinical potency of thus produced NK cells awaiting further evaluation.

Expression of Peripheral Node Addressins by Plasmacytic Plaque of Children, APACHE, TRAPP, and Primary Cutaneous Angioplasmacellular Hyperplasia

High-endothelial venules are a common feature of 3 types of cutaneous pseudolymphomas: pretibial lymphoplasmacytic plaque (PLP) of children, acral pseudolymphomatous angiokeratoma of children (APACHE), and T-cell rich angiomatoid polypoid pseudolymphoma (TRAPP). In addition, primary cutaneous angioplasmacellular hyperplasia (PCAH) overlaps with these other 3 conditions. We intend to study the expression of peripheral node addressins in PLP, APACHE, TRAPP, and PCAH. We studied 1 case of PLP, 2 cases of APACHE, 2 cases of TRAPP, and 2 cases of PCAH. Immunostainings for MECA-79 and WT-1 were obtained in all cases. All cases showed a dense lymphohistiocytic dermal inflammatory infiltrate with abundant plasma cells. In addition, HEV were prominent in all cases. Cases of PLP, APACHE, and TRAPP expressed MECA-1. Cases of PCAH did not express MECA-1. Although PLP, APACHE, and TRAPP seem to fall under the same morphologic spectrum with different clinical representations, PCAH seems to be a different entity, with histopathologic peculiarities and a different immunophenotype.

L-Selectin Enhanced T Cells Improve the Efficacy of Cancer Immunotherapy

The homing molecule, L-selectin (CD62L), is commonly used as a T cell activation marker, since expression is downregulated following engagement of the T cell receptor. Studies in mice have shown that CD62L+ central memory T cells are better at controlling tumor growth than CD62L- effector memory T cells, while L-selectin knockout T cells are poor at controlling tumor growth. Here, we test the hypothesis that T cells expressing genetically modified forms of L-selectin that are maintained following T cell activation (L-selectin enhanced T cells) are better at controlling tumor growth than wild type T cells. Using mouse models of adoptive cell therapy, we show that L-selectin enhancement improves the efficacy of CD8+ T cells in controlling solid and disseminated tumor growth. L-selectin knockout T cells had no effect. Checkpoint blockade inhibitors synergized with wild type and L-selectin enhanced T cells but had no effect in the absence of T cell transfers. Reduced tumor growth by L-selectin enhanced T cells correlated with increased frequency of CD8+ tumor infiltrating T cells 21 days after commencing therapy. Longitudinal tracking of Zirconium-89 (89Zr) labeled T cells using PET-CT showed that transferred T cells localize to tumors within 1 h and accumulate over the following 7 days. L-selectin did not promote T cell homing to tumors within 18 h of transfer, however the early activation marker CD69 was upregulated on L-selectin positive but not L-selectin knockout T cells. L-selectin positive and L-selectin knockout T cells homed equally well to tumor-draining lymph nodes and spleens. CD69 expression was upregulated on both L-selectin positive and L-selectin knockout T cells but was significantly higher on L-selectin expressing T cells, particularly in the spleen. Clonal expansion of isolated L-selectin enhanced T cells was slower, and L-selectin was linked to expression of proliferation marker Ki67. Together these findings demonstrate that maintaining L-selectin expression on tumor-specific T cells offers an advantage in mouse models of cancer immunotherapy. The beneficial role of L-selectin is unrelated to its' well-known role in T cell homing and, instead, linked to activation of therapeutic T cells inside tumors. These findings suggest that L-selectin may benefit clinical applications in T cell selection for cancer therapy and for modifying CAR-T cells to broaden their clinical scope.

Molecular Dynamics of the Association of L-Selectin and FERM Regulated by PIP2

Phosphatidylinositol 4,5-bisphosphate (PIP2) acts as a signaling lipid, mediating membrane trafficking and recruitment of proteins to membranes. A key example is the PIP2-dependent regulation of the adhesion of L-selectin to the cytoskeleton adaptors of the N-terminal subdomain of ezrin-radixin-moesin (FERM). The molecular details of the mediating behavior of multivalent anionic PIP2 lipids in this process, however, remain unclear. Here, we use coarse-grained molecular dynamics simulation to explore the mechanistic details of PIP2 in the transformation, translocation, and association of the FERM/L-selectin complex. We compare membranes of different compositions and find that anionic phospholipids are necessary for both FERM and the cytoplasmic domain of L-selectin to absorb on the membrane surface. The subsequent formation of the FERM/L-selectin complex is strongly favored by the presence of PIP2, which clusters around both proteins and triggers a conformational transition in the cytoplasmic domain of L-selectin. We are able to quantify the effect of PIP2 on the association free energy of the complex by means of a potential of mean force. We conclude that PIP2 behaves as an adhesive agent to enhance the stability of the FERM/L-selectin complex and identify key residues involved. The molecular information revealed in this study highlights the specific role of membrane lipids such as PIP2 in protein translocation and potential signaling.

Identification and characterization of a murine model of BCR‑ABL1+ acute B‑lymphoblastic leukemia with central nervous system metastasis

Breakpoint cluster region (BCR)-Abelson murine leukemia (ABL)1⁺ acute B-lymphoblastic leukemia (B-ALL) is a disease associated with a dismal prognosis and a high incidence of central nervous system (CNS) metastasis. However, BCR-ABL1⁺ B-ALL with CNS infiltration has not been previously characterized, at least to the best of our knowledge. In the present study, a murine model of BCR-ABL1⁺ B-ALL with CNS metastasis was established using retroviral transduction. The vast majority of BCR-ABL1⁺ leukemic cells were found to be immature B cells with a variable proportion of pro-B and pre-B populations. The present results indicated that the BCR-ABL1⁺ B-leukemic cells expressed high levels integrin subunit alpha 6 (Itga6) and L-selectin adhesion molecules, and have an intrinsic ability to disseminate and accumulate in CNS tissues, predominantly in meninges. On the whole, these results provide an approach for addressing the mechanisms of BCR-ABL1⁺ B-ALL with CNS metastasis and may guide the development of novel therapeutic strategies.

L-selectin: A Major Regulator of Leukocyte Adhesion, Migration and Signaling

L-selectin (CD62L) is a type-I transmembrane glycoprotein and cell adhesion molecule that is expressed on most circulating leukocytes. Since its identification in 1983, L-selectin has been extensively characterized as a tethering/rolling receptor. There is now mounting evidence in the literature to suggest that L-selectin plays a role in regulating monocyte protrusion during transendothelial migration (TEM). The N-terminal calcium-dependent (C-type) lectin domain of L-selectin interacts with numerous glycans, including sialyl Lewis X (sLe^x) for tethering/rolling and proteoglycans for TEM. Although the signals downstream of L-selectin-dependent adhesion are poorly understood, they will invariably involve the short 17 amino acid cytoplasmic tail. In this review we will detail the expression of L-selectin in different immune cell subsets, and its influence on cell behavior. We will list some of the diverse glycans known to support L-selectin-dependent adhesion, within luminal and abluminal regions of the vessel wall. We will describe how each domain within L-selectin contributes to adhesion, migration and signal transduction. A significant focus on the L-selectin cytoplasmic tail and its proposed contribution to signaling via the ezrin-radixin-moesin (ERM) family of proteins will be outlined. Finally, we will discuss how ectodomain shedding of L-selectin during monocyte TEM is essential for the establishment of front-back cell polarity, bestowing emigrated cells the capacity to chemotax toward sites of damage.

Galactosyl carbohydrate residues on hematopoietic stem/progenitor cells are essential for homing and engraftment to the bone marrow

The role of carbohydrate chains in leukocyte migration to inflamed sites during inflammation and trafficking to the lymph nodes under physiological conditions has been extensively characterized. Here, we report that carbohydrate chains also mediate the homing and engraftment of hematopoietic stem/progenitor cells (HSPCs) to the bone marrow (BM). In particular, we found that transplanted BM cells deficient in β-1,4-galactosyltransferase-1 (β4GalT-1) could not support survival in mice exposed to a lethal dose of irradiation. BM cells obtained from mice deficient in β4GalT-1 showed normal colony-forming activity and hematopoietic stem cell numbers. However, colony-forming cells were markedly rare in the BM of recipient mice 24 h after transplantation of β4GalT-1-deficient BM cells, suggesting that β4GalT-1 deficiency severely impairs homing. Similarly, BM cells with a point mutation in the UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase gene, encoding a key enzyme in sialic acid biosynthesis, showed mildly impaired homing and engraftment abilities. These results imply that the galactosyl, but not sialyl residues in glycoproteins, are essential for the homing and engraftment of HSPCs to the BM. These findings suggest the possibility of modifying carbohydrate structures on the surface of HSPCs to improve their homing and engraftment to the BM in clinical application.

Mammalian sugar-binding receptors: known functions and unexplored roles

Mammalian glycan-binding receptors, sometimes known as lectins, interact with glycans, the oligosaccharide portions of endogenous mammalian glycoproteins and glycolipids as well as sugars on the surfaces of microbes. These receptors guide glycoproteins out of and back into cells, facilitate communication between cells through both adhesion and signaling, and allow the innate immune system to respond quickly to viral, fungal, bacterial, and parasitic pathogens. For many of the roughly 100 glycan-binding receptors that are known in humans, there are good descriptions of what types of glycans they bind and how selectivity for these ligands is achieved at the molecular level. In some cases, there is also comprehensive evidence for the roles that the receptors play at the cellular and organismal levels. In addition to highlighting these well-understood paradigms for glycan-binding receptors, this review will suggest where gaps remain in our understanding of the physiological functions that they can serve.

Central memory CD8+ T cells become CD69+ tissue-residents during viral skin infection independent of CD62L-mediated lymph node surveillance

Memory CD8+ T cells in the circulation rapidly infiltrate non-lymphoid tissues following infection and provide protective immunity in an antigen-specific manner. However, the subsequent fate of memory CD8+ T cells after entering non-lymphoid tissues such as the skin during a secondary infection is largely unknown. Furthermore, because expression of CD62L is often used to identify the central memory (TCM) CD8+ T cell subset, uncoupling the physical requirement for CD62L-mediated lymph node homing versus other functional attributes of TCM CD8+ T cells remains unresolved. Here, we show that in contrast to naïve CD8+ T cells, memory CD8+ T cells traffic into the skin independent of CD62L-mediated lymph node re-activation and provide robust protective immunity against Vaccinia virus (VacV) infection. TCM, but not effector memory (TEM), CD8+ T cells differentiated into functional CD69+/CD103- tissue residents following viral clearance, which was also dependent on local recognition of antigen in the skin microenvironment. Finally, we found that memory CD8+ T cells expressed granzyme B after trafficking into the skin and utilized cytolysis to provide protective immunity against VacV infection. Collectively, these findings demonstrate that TCM CD8+ T cells become cytolytic following rapid infiltration of the skin to protect against viral infection and subsequently differentiate into functional CD69+ tissue-residents.

Pak1 Kinase Promotes Activated T Cell Trafficking by Regulating the Expression of L-Selectin and CCR7

Normal function of the adaptive immune system requires trafficking of T cells between the blood and lymphoid organs. Lymphocyte homing to lymph nodes requires that they cross endothelial barriers present in blood vessels and lymphatics. This multi-step process requires a remodeling of the lymphocyte plasma membrane, which is mediated by the dynamic re-arrangement of the actin cytoskeleton. Pak1 plays a central role in cell morphology, adhesion and migration in various cell types. Here we demonstrate that Pak1 is required for activated CD4⁺ T cell trafficking to lymph nodes. Pak1 deficiency in T cells causes a defect in the transcription of CCR7 and L-selectin, thereby altering lymphocyte trafficking. Additionally, we report an increase in L-selectin shedding in Pak1-deficient T cells, which correlates with a decrease in the recruitment of calmodulin to the cytoplasmic tail of L-selectin during T cell activation. Overall, our findings demonstrate that by regulating the expression of two major lymph node homing molecules, L-selectin and CCR7, Pak1 mediates activated CD4⁺ T cell trafficking.

Fucosylation Enhances the Efficacy of Adoptively Transferred Antigen-Specific Cytotoxic T Lymphocytes

PURPOSE

Inefficient homing of adoptively transferred cytotoxic T lymphocytes (CTLs) to tumors is a major limitation to the efficacy of adoptive cellular therapy (ACT) for cancer. However, through fucosylation, a process whereby fucosyltransferases (FT) add fucose groups to cell surface glycoproteins, this challenge may be overcome. Endogenously fucosylated CTLs and ex vivo fucosylated cord blood stem cells and regulatory T cells were shown to preferentially home to inflamed tissues and marrow. Here, we show a novel approach to enhance CTL homing to leukemic marrow and tumor tissue.

EXPERIMENTAL DESIGN

Using the enzyme FT-VII, we fucosylated CTLs that target the HLA-A2-restricted leukemia antigens CG1 and PR1, the HER2-derived breast cancer antigen E75, and the melanoma antigen gp-100. We performed in vitro homing assays to study the effects of fucosylation on CTL homing and target killing. We used in vivo mouse models to demonstrate the effects of ex vivo fucosylation on CTL antitumor activities against leukemia, breast cancer, and melanoma.

RESULTS

Our data show that fucosylation increases in vitro homing and cytotoxicity of antigen-specific CTLs. Furthermore, fucosylation enhances in vivo CTL homing to leukemic bone marrow, breast cancer, and melanoma tissue in NOD/SCID gamma (NSG) and immunocompetent mice, ultimately boosting the antitumor activity of the antigen-specific CTLs. Importantly, our work demonstrates that fucosylation does not interfere with CTL specificity.

CONCLUSIONS

Together, our data establish ex vivo CTL fucosylation as a novel approach to improving the efficacy of ACT, which may be of great value for the future of ACT for cancer.

Circadian Expression of Migratory Factors Establishes Lineage-Specific Signatures that Guide the Homing of Leukocyte Subsets to Tissues

The number of leukocytes present in circulation varies throughout the day, reflecting bone marrow output and emigration from blood into tissues. Using an organism-wide circadian screening approach, we detected oscillations in pro-migratory factors that were distinct for specific vascular beds and individual leukocyte subsets. This rhythmic molecular signature governed time-of-day-dependent homing behavior of leukocyte subsets to specific organs. Ablation of BMAL1, a transcription factor central to circadian clock function, in endothelial cells or leukocyte subsets demonstrated that rhythmic recruitment is dependent on both microenvironmental and cell-autonomous oscillations. These oscillatory patterns defined leukocyte trafficking in both homeostasis and inflammation and determined detectable tumor burden in blood cancer models. Rhythms in the expression of pro-migratory factors and migration capacities were preserved in human primary leukocytes. The definition of spatial and temporal expression profiles of pro-migratory factors guiding leukocyte migration patterns to organs provides a resource for the further study of the impact of circadian rhythms in immunity.

A novel and accurate microfluidic assay of CD62L in bladder cancer serum samples

We report a low-cost, sensitive, bead-based electrochemical immunoarray for soluble L-selectin (or CD62L protein), a potential biomarker for staging bladder cancer. We used a semi-automated modular microfluidic array with online antigen capture on superparamagnetic beads, which were subsequently delivered to a detection chamber housing multiple sensors. The assay was designed to accurately detect CD62L in diluted serum with a limit of detection (LOD) of 0.25 ng mL-1 and a dynamic range of 0.25-100 ng mL-1. The microfluidic array gave significantly better accuracy and higher sensitivity than a standard ELISA kit, which was shown to be subject to significant systematic error at high and low concentration ranges. 31 serum samples from patients with varying grades of bladder cancer and cancer-free controls were analyzed by the immunoarray and ELISA, and the CD62L levels correlated. This work establishes a new accurate assay for determining CD62L levels and highlights the potential of this protein as a biomarker for detecting locoregional progression of bladder cancer.

Neutrophil-mediated delivery of pixantrone-loaded liposomes decorated with poly(sialic acid)-octadecylamine conjugate for lung cancer treatment

Poly(sialic acid) (PSA) is a natural hydrophilic biodegradable and non-immunogenic biopolymer, receptors for its monomer are expressed on peripheral blood neutrophils (PBNs), which plays important roles in the progression and invasion of tumors. A poly(sialic acid)-octadecylamine conjugate (PSA-ODA) was synthesized and then anchor it on the surface of liposomal pixantrone (Pix-PSL), to achieve an improved anticancer effect. The liposomes were prepared using a remote loading method via a pH gradient, and then assessed for particle size, zeta potential encapsulation efficiency, in vitro release, and in vitro cytotoxicity. Simultaneously, in vitro and in vivo cellular uptake studies confirmed that PSA-decorated liposomes provided an enhanced accumulation of liposomes in PBNs. An in vivo study presented that the anti-tumor activity of Pix-PSL was superior to that of other Pix formulations, probably due to the efficient targeting of PBNs by Pix-PSL, after which PBN containing Pix-PSL (Pix-PSL/PBNs) in the blood circulation are recruited by the tumor microenvironment. These findings suggest that PSA-decorated liposomal Pix may provide a neutrophil-mediated drug delivery system (DDS) for the eradication of tumors, which represents a promising approach for the tumor targeting of chemotherapeutic treatments.

The Chinese herbal formula Zhibai Dihuang Granule treat Yin-deficiency-heat syndrome rats by regulating the immune responses

ETHNOPHARMACOLOGICAL RELEVANCE

Zhibai Dihuang Granule (ZDG), a traditional Chinese medicine (TCM) made from eight Chinese herbs, has been classically used to treat Yin-deficiency-heat (YDH) syndrome. ZDG is well known with the therapeutic efficacy of nourishing Yin and decreasing internal heat in clinic, but the mechanism of ZDG's therapeutic effect is still not clear.

MATERIALS AND METHODS

High doses of triiodothyronine (T3) were given intraperitoneally to induce Hyperthyroid YDH syndrome in SD rats. The animals were then treated with ZDG for one week. The iTRAQ-coupled with two-dimensional liquid chromatography-tandem mass spectrometry (2D LC-MS/MS) technique was used to screen the differentially expressed serum proteins between ZDG treated rats and YDH syndrome rats. The differentially expressed proteins were analyzed by bioinformatics method and were verified by enzyme-linked immunosorbent assay (ELISA).

RESULTS

A total of 55 differentially expressed proteins were identified, including 23 up-regulated proteins (>1.25 fold, p < 0.05) and 32 down-regulated proteins (<0.80 fold, p < 0.05). Among the differentially expressed proteins, 26 proteins returned to normal after ZDG treatment. Bioinformatics analysis showed that these proteins were mainly involved in immune response, including regulation of immune system process, complement activation, and humoral immune response mediated by circulating immunoglobulin. ELISA revealed significantly increased levels of Zinc-alpha-2-glycoprotein (Azgp1), L-selectin, C-reactive protein (Crp), Plasminogen (Plg), Kininogen 1 (Kng1), and significantly decreased levels of Mannose binding lectin 2 (Mbl2) and Complement C1qb chain (C1qb) in ZDG treated rats compared with YDH syndrome rats. Bioinformatics analyses indicated that Azgp1 participated in antigen processing and presentation, Crp, C1qb, and Mbl2 were involved in complement activation, while L-selectin, Plg, and Kng1 were involved in regulating the inflammatory response.

CONCLUSIONS

Our study provides experimental evidence to understand the therapeutic mechanism of ZDG in YDH syndrome. The results suggested that ZDG may regulate the complement activation and inflammatory response, and promote the ability to recognize antigens to alleviate YDH syndrome.

Gut-Selective Integrin-Targeted Therapies for Inflammatory Bowel Disease

Integrins are cell surface receptors with bidirectional signalling capabilities that can bind to adhesion molecules in order to mediate homing of leukocytes to peripheral tissues. Gut-selective leukocyte homing is facilitated by interactions between α4β7 and its ligand, mucosal addressin cellular adhesion molecule-1 [MAdCAM-1], while retention of lymphocytes in mucosal tissues is mediated by αEβ7 binding to its ligand E-cadherin. Therapies targeting gut-selective trafficking have shown efficacy in inflammatory bowel disease [IBD], confirming the importance of leukocyte trafficking in disease pathobiology. This review will provide an overview of integrin structure, function and signalling, and highlight the role that these molecules play in leukocyte homing and retention. Anti-integrin therapeutics, including gut-selective antibodies against the β7 integrin subunit [etrolizumab] and the α4β7 integrin heterodimer [vedolizumab and abrilumab], and the non-gut selective anti-α4 integrin [natalizumab], will be discussed, as well as novel targeting approaches using small molecules.

Genetic Defects in Phosphoinositide 3-Kinase δ Influence CD8+ T Cell Survival, Differentiation, and Function

Activated phosphoinositide 3-kinase delta syndrome (APDS), also known as p110 delta-activating mutation causing senescent T cells, lymphadenopathy and immunodeficiency (PASLI), is an autosomal dominant primary human immunodeficiency (PID) caused by heterozygous gain-of-function mutations in PIK3CD, which encodes the p110δ catalytic subunit of PI3K. This recently described PID is characterized by diverse and heterogeneous clinical manifestations that include recurrent respiratory infections, lymphoproliferation, progressive lymphopenia, and defective antibody responses. A major clinical manifestation observed in the NIH cohort of patients with PIK3CD mutations is chronic Epstein-Barr virus (EBV) and/or cytomegalovirus viremia. Despite uncontrolled EBV infection, many APDS/PASLI patients had normal or higher frequencies of EBV-specific CD8⁺ T cells. In this review, we discuss data pertaining to CD8⁺ T cell function in APDS/PASLI, including increased cell death, expression of exhaustion markers, and altered killing of autologous EBV-infected B cells, and how these and other data on PI3K provide insight into potential cellular defects that prevent clearance of chronic infections.

The Many and Varied Roles of Tetraspanins in Immune Cell Recruitment and Migration

Immune cell recruitment and migration is central to the normal functioning of the immune system in health and disease. Numerous adhesion molecules on immune cells and the parenchymal cells they interact with are well recognized for their roles in facilitating the movements of immune cells throughout the body. A growing body of evidence now indicates that tetraspanins, proteins known for their capacity to organize partner molecules within the cell membrane, also have significant impacts on the ability of immune cells to migrate around the body. In this review, we examine the tetraspanins expressed by immune cells and endothelial cells that influence leukocyte recruitment and motility and describe their impacts on the function of adhesion molecules and other partner molecules that modulate the movements of leukocytes. In particular, we examine the functional roles of CD9, CD37, CD63, CD81, CD82, and CD151. This reveals the diversity of the functions of the tetraspanin family in this setting, both in the nature of adhesive and migratory interactions that they regulate, and the positive or inhibitory effects mediated by the individual tetraspanin proteins.

Targeted delivery of pixantrone to neutrophils by poly(sialic acid)-p-octadecylamine conjugate modified liposomes with improved antitumor activity

Based on the knowledge that poly(sialic acid) is a critical element for tumour development and that the receptors for its monomer are expressed on neutrophils, which play important roles in the progression and invasion of tumours, a poly(sialic acid)-p-octadecylamine conjugate (PSA-p-ODA) was synthesised and used to modify the surface of liposomal pixantrone (Pix-PSL) to improve the delivery of Pix to peripheral blood neutrophils (PBNs). The liposomes were fabricated using a remote loading technology via a pH gradient, and were then assessed for particle size, encapsulation efficiency, in vitro release, in vitro cytotoxicity, and pharmacokinetics. Simultaneously, in vitro and in vivo cellular uptake studies demonstrated that Pix-PSL provided an enhanced accumulation of Pix in PBNs. An in vivo study showed that the anti-tumour activity of Pix-PSL was superior to that of other formulations, probably owing to the efficient targeting of PBNs by Pix-PSL, after which PBNs containing Pix-PSL (Pix-PSL/PBNs) in the circulatory system are recruited by the tumour microenvironment. These findings suggest that PSA-p-ODA-decorated liposomal Pix may provide a neutrophil-mediated drug delivery system (DDS) for the eradication of tumours, and thus represents a promising approach for the tumour targeting of chemotherapeutic treatments.

Adoptive cancer immunotherapy using DNA-demethylated T helper cells as antigen-presenting cells

In cancer cells, cancer/testis (CT) antigens become epigenetically derepressed through DNA demethylation and constitute attractive targets for cancer immunotherapy. Here we report that activated CD4⁺ T helper cells treated with a DNA-demethylating agent express a broad repertoire of endogenous CT antigens and can be used as antigen-presenting cells to generate autologous cytotoxic T lymphocytes (CTLs) and natural killer cells. In vitro, activated CTLs induce HLA-restricted lysis of tumor cells of different histological types, as well as cells expressing single CT antigens. In a phase 1 trial of 25 patients with recurrent glioblastoma multiforme, cytotoxic lymphocytes homed to the tumor, with tumor regression ongoing in three patients for 14, 22, and 27 months, respectively. No treatment-related adverse effects were observed. This proof-of-principle study shows that tumor-reactive effector cells can be generated ex vivo by exposure to antigens induced by DNA demethylation, providing a novel, minimally invasive therapeutic strategy for treating cancer.

Cord blood-derived T cells allow the generation of a more naïve tumor-reactive cytotoxic T-cell phenotype

BACKGROUND

Transplantation of hematopoietic stem cells (HSCs) from peripheral blood (PB) or cord blood (CB) is well established. HSCs from CB are associated with a lower risk of graft-versus-host disease (GVHD), but antigen-independent expanded CB- and PB-derived T cells can induce GVHD in allo-HSC recipients. CB-derived cells might be more suitable for adoptive immunotherapy as they have unique T-cell characteristics. Here, we describe functional differences between CB and PB T cells stimulated with different cytokine combinations involved in central T-cell activation.

STUDY DESIGN AND METHODS

Isolated CD8+ T cells from CB and PB were stimulated antigen independently with anti-CD3/CD28 stimulator beads or in an antigen-dependent manner with artificial antigen-presenting cells loaded with the HLA-A*02:01-restricted peptide of tumor-associated melanoma antigen recognized by T cells 1 (MART1). CB and PB T cells cultured in the presence of interleukin (IL)-7, IL-15, IL-12, and IL-21 were characterized for T-cell phenotype and specificity, that is, by CD107a, interferon-γ, tumor necrosis factor-α, and IL-2 expression.

RESULTS

After antigen-independent stimulation, activated CD8+ CB T cells exhibited stronger proliferation and function than those from PB. After antigenic stimulation, MART1-reactive CB T cells were naïve (CD45RA+CCR7+), cytotoxic, and highly variable in expressing homing marker CD62L. Addition of IL-21 resulted in increased T-cell proliferation, whereas supplementation with IL-12 decreased IL-21-induced expansion, but increased the functionality and cytotoxicity of CB and PB T cells.

CONCLUSION

MART1-reactive CB T cells with a more naïve phenotype and improved properties for homing can be generated. The results contribute to better understanding the effects on GVHD and graft versus tumor.

Lack of Ikaros cripples expression of Foxo1 and its targets in naive T cells

Ikaros is a transcription factor that regulates lymphocyte development from the level of the haematopoietic stem cell. Lack of Ikaros reduces the ability of progenitor cells to commit to the T-cell lineage, resulting in reduced numbers of early thymic T-cell progenitors and mature T cells. Mature CD4 T cells that lack Ikaros have defects in proliferation, T helper cell differentiation, cytokine expression and the ability to become anergic. A role for Ikaros in the naive T cell has not yet been identified. The receptors interleukin-7 receptor α (IL-7Rα) and l-selectin are important for ensuring survival and proper homing of naive T cells, respectively. Here we show that lack of Ikaros leads to reduced expression of these receptors in naive T cells, which impacts their ability to home and survive in response to IL-7. We define the mechanism underlying this phenotype as a requirement for Ikaros in maintenance of expression of Foxo1, a transcriptional regulator that is required for their expression. We also demonstrate that CD4 T cells lacking Ikaros are significantly crippled in their ability to become induced regulatory T cells, a phenotype also linked to reduced Foxo1 expression. Finally, we show that restoring Ikaros function to Ikaros-deficient CD4 T cells increases levels of Foxo1 message. Together, these studies define, for the first time, a role for Ikaros in naive T cells and establish it as the first transcriptional regulator required for maintaining levels of Foxo1 gene expression in these cells.

β7-Integrin and MAdCAM-1 play opposing roles during the development of non-alcoholic steatohepatitis

BACKGROUND & AIMS

Non-alcoholic steatohepatitis (NASH) is a leading cause of chronic liver disease in Western countries. It is unclear how infiltrating leukocytes affect NASH-development. Our study aims to investigate the role of the homing/receptor, pair mucosal addressin cell adhesion molecule-1 (MAdCAM-1)/β₇-Integrin, on immune cell recruitment and disease progression in a steatohepatitis model.

METHODS

Constitutive β₇-Integrin deficient (β₇^-/-) and MAdCAM-1 deficient (MAdCAM-1^-/-) mice were fed a high fat diet (HFD) for 26weeks or methionine-choline-deficient-diet (MCD) for 4weeks.

RESULTS

β₇^-/- mice displayed earlier and more progressive steatohepatitis during HFD- and MCD-treatment, while MAdCAM-1^-/- mice showed less histomorphological changes. The anti-oxidative stress response was significantly weaker in β₇^-/- mice as reflected by a significant downregulation of the transcription factors nuclear-factor(erythroid-derived 2)-like 2 (Nrf2) and heme-oxigenase-1 (HO-1). Additionally, stronger dihydroethidium-staining revealed an increased oxidative stress response in β₇^-/- animals. In contrast, MAdCAM-1^-/- mice showed an upregulation of the anti-oxidative stress response. β₇^-/- animals exhibited stronger hepatic infiltration of inflammatory cells, especially neutrophils, reflecting earlier steatohepatitis initiation. Expression of regulatory T cell (T_Reg) markers as well as numbers of anti-inflammatory macrophages was significantly enhanced in MAdCAM-1^-/- mice. Those changes finally resulted in earlier and stronger collagen accumulation in β₇^-/- mice, whereas MAdCAM-1^-/- mice were protected from fibrosis initiation.

CONCLUSIONS

Adhesion molecule mediated effector cell migration contributes to the outcome of steatohepatitis in the HFD- and the MCD model. While MAdCAM-1 promotes steatohepatitis, β₇-Integrin unexpectedly exerts protective effects. β₇^-/- mice show earlier steatohepatitis initiation and significantly stronger fibrosis progression. Accordingly, the interaction of β₇-Integrins and their receptor MAdCAM-1 provide novel targets for therapeutic interventions in steatohepatitis.

LAY SUMMARY

The mucosal addressin cell adhesion molecule 1 (MAdCAM-1) is expressed in livers upon diet-induced non-alcoholic steatohepatitis (NASH). Loss of MAdCAM-1 has beneficial effects regarding the development of NASH - manifested by reduced hepatic oxidative stress and decreased inflammation. In contrast, β₇-Integrin-deficiency results in increased steatohepatitis.

Regulation of T Cell Trafficking by Enzymatic Synthesis of O-Glycans

Selectins constitute a family of oligosaccharide binding proteins that play critical roles in regulating the trafficking of leukocytes. In T cells, L-selectin (CD62L) controls the capacity for naive and memory T cells to actively survey peripheral lymph nodes, whereas P- and E-selectin capture activated T cells on inflamed vascular endothelium to initiate extravasation into non-lymphoid tissues. The capacity for T cells to interact with all of these selectins is dependent on the enzymatic synthesis of complex O-glycans, and thus, this protein modification plays an indispensable role in regulating the distribution and homing of both naive and previously activated T cells in vivo. In contrast to neutrophils, O-glycan synthesis is highly dynamic in T cell populations and is largely controlled by extracellular stimuli such as antigen recognition or signaling though cytokine receptors. Herein, we review the basic principles of enzymatic synthesis of complex O-glycans, discuss tools and reagents for studying this type of protein modification and highlight our current understanding of how O-glycan synthesis is regulated and subsequently impacts the trafficking potential of diverse T cell populations.

L-selectin mechanochemistry restricts neutrophil priming in vivo

Circulating neutrophils must avoid premature activation to prevent tissue injury. The leukocyte adhesion receptor L-selectin forms bonds with P-selectin glycoprotein ligand-1 (PSGL-1) on other leukocytes and with peripheral node addressin (PNAd) on high endothelial venules. Mechanical forces can strengthen (catch) or weaken (slip) bonds between biological molecules. How these mechanochemical processes influence function in vivo is unexplored. Here we show that mice expressing an L-selectin mutant (N138G) have altered catch bonds and prolonged bond lifetimes at low forces. Basal lymphocyte homing and neutrophil recruitment to inflamed sites are normal. However, circulating neutrophils form unstable aggregates and are unexpectedly primed to respond robustly to inflammatory mediators. Priming requires signals transduced through L-selectin N138G after it engages PSGL-1 or PNAd. Priming enhances bacterial clearance but increases inflammatory injury and enlarges venous thrombi. Thus, L-selectin mechanochemistry limits premature activation of neutrophils. Our results highlight the importance of probing how mechanochemistry functions in vivo.

The cytoplasmic tail of L-selectin interacts with the adaptor-protein complex AP-1 subunit μ1A via a novel basic binding motif

L-selectin regulates leukocyte adhesion and rolling along the endothelium. Proteins binding to the cytoplasmic tail of L-selectin regulate L-selectin functions. We used L-selectin cytoplasmic tail peptide pulldown assays combined with high sensitivity liquid chromatography/mass spectrometry to identify novel L-selectin tail-binding proteins. Incubation of the L-selectin tail with cell extracts from phorbol 12-myristate 13-acetate-stimulated Raw 264.7 macrophages resulted in the binding of μ1A of the clathrin-coated vesicle AP-1 complex. Furthermore, full-length GST-μ1A and the GST-μ1A C-terminal domain, but not the GST-μ1A N-terminal domain, bind to L-selectin tail peptide, and the intracellular pool of L-selectin colocalizes with AP-1 at the trans-Golgi network. We identified a novel basic protein motif consisting of a cluster of three dibasic residues (³⁵⁶RR³⁵⁷, ³⁵⁹KK³⁶⁰, and ³⁶²KK³⁶³) in the membrane-proximal domain of the L-selectin tail as well as a doublet of aspartic acid residues (³⁶⁹DD³⁷⁰) in the membrane-distal end of the L-selectin tail involved in μ1A binding. Stimulation of Raw 264.7 macrophages with PMA augmented the amount of μ1A associated with anti-L-selectin immunoprecipitates. However, full-length GST-μ1A did not bind to the phospho-L-selectin tail or phospho-mimetic S364D L-selectin tail. Accordingly, we propose that phosphorylation of μ1A is required for interaction with the L-selectin tail and that L-selectin tail phosphorylation may regulate this interaction in vivo Molecular docking of the L-selectin tail to μ1A was used to identify the μ1A surface domain binding the L-selectin tail and to explain how phosphorylation of the L-selectin tail abrogates μ1A interaction. Our findings indicate that L-selectin is transported constitutively by the AP-1 complex, leading to the formation of a trans-Golgi network reserve pool and that phosphorylation of the L-selectin tail blocks AP-1-dependent retrograde transport of L-selectin.

High Endothelial Venules and Other Blood Vessels: Critical Regulators of Lymphoid Organ Development and Function

The blood vasculature regulates both the development and function of secondary lymphoid organs by providing a portal for entry of hemopoietic cells. During the development of lymphoid organs in the embryo, blood vessels deliver lymphoid tissue inducer cells that initiate and sustain the development of lymphoid tissues. In adults, the blood vessels are structurally distinct from those in other organs due to the requirement for high levels of lymphocyte recruitment under non-inflammatory conditions. In lymph nodes (LNs) and Peyer's patches, high endothelial venules (HEVs) especially adapted for lymphocyte trafficking form a spatially organized network of blood vessels, which controls both the type of lymphocyte and the site of entry into lymphoid tissues. Uniquely, HEVs express vascular addressins that regulate lymphocyte entry into lymphoid organs and are, therefore, critical to the function of lymphoid organs. Recent studies have demonstrated important roles for CD11c+ dendritic cells in the induction, as well as the maintenance, of vascular addressin expression and, therefore, the function of HEVs. Tertiary lymphoid organs (TLOs) are HEV containing LN-like structures that develop inside organized tissues undergoing chronic immune-mediated inflammation. In autoimmune lesions, the development of TLOs is thought to exacerbate disease. In cancerous tissues, the development of HEVs and TLOs is associated with improved patient outcomes in several cancers. Therefore, it is important to understand what drives the development of HEVs and TLOs and how these structures contribute to pathology. In several human diseases and experimental animal models of chronic inflammation, there are some similarities between the development and function of HEVs within LN and TLOs. This review will summarize current knowledge of how hemopoietic cells with lymphoid tissue-inducing, HEV-inducing, and HEV-maintaining properties are recruited from the bloodstream to induce the development and control the function of lymphoid organs.

A high migratory capacity of donor T-cells in response to the lymph node homing receptor CCR7 increases the incidence and severity of GvHD

The pathogenesis of GvHD involves migration of donor T-cells into the secondary lymphoid organs in the recipient, which is steered by two homing molecules, CD62L and CCR7. Therefore, we investigated whether the migratory capacity of donor T-cells is associated with GvHD. This single center prospective study included 85 donor-recipient pairs. In vitro chemotaxis assays of the lymphocytes of the apheresis product were performed in parallel to the analysis of CD62L and CCR7 by flow cytometry. The migratory index to the CCR7 ligands, CCL19 and CCL21, was higher in T-cells from donors whose recipients will develop GvHD. Similarly, the acute GvHD (aGvHD) group received higher percentage of CD4+CCR7+ T-cells, whereas chronic GvHD (cGvHD) patients were transplanted with higher percentages of CD8+CCR7+ T-cells compared with the non-GvHD group. These results were confirmed when patients were subdivided according to degrees of severity. Further, multivariate analysis confirmed that the proportions of CCR7+ CD4+ and CCR7+ CD8+ T-cells are risk factors for the development and severity of aGvHD and cGvHD, respectively. Functional experiments demonstrated that CCR7+ T-cells exhibited higher potential for activation than CCR7- T-cells did. We therefore propose that the selective depletion of CCR7-expressing T-cells may be an effective preventive therapy for GvHD.

Increased FcγRIIB dominance contributes to the emergence of resistance to therapeutic antibodies in chronic lymphocytic leukaemia patients

Resistance to therapeutic antibodies in chronic lymphocytic leukaemia (CLL) is common. In this study, we show that therapeutic antibodies against CD62L (CD62L-Ab) or CD20 (obinutuzumab) were able to induce antibody-dependent cell-mediated cytotoxicity (ADCC) and phagocytosis (ADP) in primary cultures of CLL cells. CLL cells derived from patients with active disease requiring treatment displayed resistance to these antibodies, whereas patients with stable disease were sensitive. Using enrichment strategies and transcriptomic analyses, we show that antibody-dependent tumour cell killing was FcγR-dependent and mediated by macrophages. Moreover, we show that resistance cannot be attributed to total numbers or established subtypes of monocytes/macrophages, or the efficiency with which they bind an immune complex. Rather, ADCC/ADP resistance was due to reduced signalling activity through the activating FcγRs resulting in the transfer of dominance to the inhibitory FcγRIIb within macrophages. Most significantly, we show that resistance is an actionable event that could be reversed using inhibitors of FcγRIIb signalling in primary cultures of CLL cells that were previously insensitive to obinutuzumab or CD62L-Ab.

Involvement of L-selectin expression in Burkholderia pseudomallei-infected monocytes invading the brain during murine melioidosis

The development of neurologic melioidosis was linked to the elicitation of Burkholderia pseudomallei-infected L-selectin^hiCD11b⁺ BALB/c cells in our previous study. However, whether monocytic L-selectin (CD62L, encoded by the sell gene) is a key factor remains uncertain. In the present study, after establishing multi-organ foci via hematogenous routes, we demonstrated that B. pseudomallei GFP steadily persisted in blood, splenic, hepatic and bone marrow (BM) Ly6C monocytes; however, the circulating CD16/32⁺CD45^hiGFP⁺ brain-infiltrating leukocytes (BILs) derived from the blood Ly6C monocytes were expanded in BALB/c but not in C57BL/6 bacteremic melioidosis. Consistent with these results, 60% of BALB/c mice but only 10% of C57BL/6 mice exhibited neurologic melioidosis. In a time-dependent manner, B. pseudomallei invaded C57BL/6 BM-derived phagocytes and monocytic progenitors by 2 d. The number of Ly6C⁺CD62L⁺GFP⁺ inflamed cells that had expanded in the BM and that were ready for emigration peaked on d 21 post-infection. Hematogenous B. pseudomallei-loaded sell^+/+Ly6C monocytes exacerbated the bacterial loads and the proportion of Ly6C⁺GFP⁺ BILs in the recipient brains compared to sell^-/- infected Ly6C cells when adoptively transferred. Moreover, a neutralizing anti-CD62L antibody significantly depleted the bacterial colonization of the brain following adoptive transfer of B. pseudomallei-loaded C57BL/6 or BALB/c Ly6C cells. Our data thus suggest that Ly6C⁺CD62L⁺ infected monocytes served as a Trojan horse across the cerebral endothelium to induce brain infection. Therefore, CD62L should be considered as not only a temporally elicited antigen but also a disease-relevant leukocyte marker during the development of neurologic melioidosis.

Effects of whole flaxseed, raw soybeans, and calcium salts of fatty acids on measures of cellular immune function of transition dairy cows

The objective of the current study was to evaluate the effects of supplemental n-3 and n-6 fatty acid (FA) sources on cellular immune function of transition dairy cows. Animals were randomly assigned to receive 1 of 4 diets: control (n=11); whole flaxseed (n-3 FA source; n=11), 60 and 80g/kg of whole flaxseed [diet dry matter (DM) basis] during pre- and postpartum, respectively; whole raw soybeans (n-6 FA source; n=10), 120 and 160g/kg of whole raw soybeans (diet DM basis) during pre- and postpartum, respectively; and calcium salts of unsaturated FA (Megalac-E, n-6 FA source; n=10), 24 and 32g/kg of calcium salts of unsaturated FA (diet DM basis) during pre- and postpartum, respectively. Supplemental FA did not alter DM intake and milk yield but increased energy balance during the postpartum period. Diets containing n-3 and n-6 FA sources increased phagocytosis capacity of leukocytes and monocytes and phagocytosis activity of monocytes. Furthermore, n-3 FA source increased phagocytic capacity of leukocytes and neutrophils and increased phagocytic activity in monocytes and neutrophils when compared with n-6 FA sources. Supplemental FA effects on adaptive immune system included increased percentage of T-helper cells, T-cytotoxic cells, cells that expressed IL-2 receptors, and CD62 adhesion molecules. The results of this study suggest that unsaturated FA can modulate innate and adaptive cellular immunity and trigger a proinflammatory response. The n-3 FA seems to have a greater effect on phagocytic capacity and activity of leukocytes when compared with n-6 FA.

Effector, Memory, and Dysfunctional CD8(+) T Cell Fates in the Antitumor Immune Response

The adaptive immune system plays a pivotal role in the host's ability to mount an effective, antigen-specific immune response against tumors. CD8(+) tumor-infiltrating lymphocytes (TILs) mediate tumor rejection through recognition of tumor antigens and direct killing of transformed cells. In growing tumors, TILs are often functionally impaired as a result of interaction with, or signals from, transformed cells and the tumor microenvironment. These interactions and signals can lead to transcriptional, functional, and phenotypic changes in TILs that diminish the host's ability to eradicate the tumor. In addition to effector and memory CD8(+) T cells, populations described as exhausted, anergic, senescent, and regulatory CD8(+) T cells have been observed in clinical and basic studies of antitumor immune responses. In the context of antitumor immunity, these CD8(+) T cell subsets remain poorly characterized in terms of fate-specific biomarkers and transcription factor profiles. Here we discuss the current characterization of CD8(+) T cell fates in antitumor immune responses and discuss recent insights into how signals in the tumor microenvironment influence TIL transcriptional networks to promote CD8(+) T cell dysfunction.

CCR5+T-bet+FoxP3+ Effector CD4 T Cells Drive Atherosclerosis

RATIONALE

CD4 T cells are involved in the pathogenesis of atherosclerosis, but atherosclerosis-specific CD4 T cells have not been described. Moreover, the chemokine(s) that regulates T-cell trafficking to the atherosclerotic lesions is also unknown.

OBJECTIVE

In Apoe(-/-) mice with mature atherosclerotic lesions (5 months of high fat diet), we find that most aortic T cells express CCR5 and interferon-γ with a unique combination of cell surface markers (CD4(+)CD25(-)CD44(hi)CD62L(lo)) and transcription factors (FoxP3(+)T-bet(+)). We call these cells CCR5Teff. We investigated the role of CCR5 in regulating T-cell homing to the atherosclerotic aorta and the functionality of the CCR5Teff cells.

METHODS AND RESULTS

CCR5Teff cells are exclusively found in the aorta and para-aortic lymph nodes of Apoe(-/-) mice. They do not suppress T-cell proliferation in vitro and are less potent than regulatory T cells at inhibiting cytokine secretion. Blocking or knocking out CCR5 or its ligand CCL5 significantly blocks T-cell homing to atherosclerotic aortas. Transcriptomic analysis shows that CCR5Teff cells are more similar to effector T cells than to regulatory T cells. They secrete interferon-γ, interleukin-2, interleukin-10, and tumor necrosis factor. Adoptive transfer of these CCR5Teff cells significantly increases atherosclerosis.

CONCLUSIONS

CCR5 is specifically needed for CD4 T-cell homing to the atherosclerotic plaques. CCR5(+)CD4 T cells express an unusual combination of transcription factors, FoxP3 and T-bet. Although CCR5Teff express FoxP3, we showed that they are not regulatory and adoptive transfer of these cells exacerbates atherosclerosis.

Late stages of T cell maturation in the thymus involve NF-κB and tonic type I interferon signaling

Positive selection occurs in the thymic cortex, but critical maturation events occur later in the medulla. Here we defined the precise stage at which T cells acquired competence to proliferate and emigrate. Transcriptome analysis of late gene changes suggested roles for the transcription factor NF-κB and interferon signaling. Mice lacking the inhibitor of NF-κB (IκB) kinase (IKK) kinase TAK1 underwent normal positive selection but exhibited a specific block in functional maturation. NF-κB signaling provided protection from death mediated by the cytokine TNF and was required for proliferation and emigration. The interferon signature was independent of NF-κB; however, thymocytes deficient in the interferon-α (IFN-α) receptor IFN-αR showed reduced expression of the transcription factor STAT1 and phenotypic abnormality but were able to proliferate. Thus, both NF-κB and tonic interferon signals are involved in the final maturation of thymocytes into naive T cells.

Interleukin-6 Induced "Acute" Phenotypic Microenvironment Promotes Th1 Anti-Tumor Immunity in Cryo-Thermal Therapy Revealed By Shotgun and Parallel Reaction Monitoring Proteomics

Cryo-thermal therapy has been emerged as a promising novel therapeutic strategy for advanced breast cancer, triggering higher incidence of tumor regression and enhanced remission of metastasis than routine treatments. To better understand its anti-tumor mechanism, we utilized a spontaneous metastatic mouse model and quantitative proteomics to compare N-glycoproteome changes in 94 serum samples with and without treatment. We quantified 231 highly confident N-glycosylated proteins using iTRAQ shotgun proteomics. Among them, 53 showed significantly discriminated regulatory patterns over the time course, in which the acute phase response emerged as the most enhanced pathway. The anti-tumor feature of the acute response was further investigated using parallel reaction monitoring target proteomics and flow cytometry on 23 of the 53 significant proteins. We found that cryo-thermal therapy reset the tumor chronic inflammation to an “acute” phenotype, with up-regulation of acute phase proteins including IL-6 as a key regulator. The IL-6 mediated “acute” phenotype transformed IL-4 and Treg-promoting ICOSL expression to Th1-promoting IFN-γ and IL-12 production, augmented complement system activation and CD86⁺MHCII⁺ dendritic cells maturation and enhanced the proliferation of Th1 memory cells. In addition, we found an increased production of tumor progression and metastatic inhibitory proteins under such “acute” environment, favoring the anti-metastatic effect. Moreover, cryo-thermal on tumors induced the strongest “acute” response compared to cryo/hyperthermia alone or cryo-thermal on healthy tissues, accompanying by the most pronounced anti-tumor immunological effect. In summary, we demonstrated that cryo-thermal therapy induced, IL-6 mediated “acute” microenvironment shifted the tumor chronic microenvironment from Th2 immunosuppressive and pro-tumorigenic to Th1 immunostimulatory and tumoricidal state. Moreover, the magnitude of “acute” and “danger” signals play a key role in determining the efficacy of anti-tumor activity.

Effect of feeding whole compared with cell-free colostrum on calf immune status: Vaccination response

Vaccination contributes to improved herd health and production. Boosting immune development at a young age may have long-term effects by enhancing vaccine immune response and efficacy. In the bovine, colostrum is the sole source of maternal immunity, having a substantial effect on health status in the neonate. To date, colostral antibody concentration is used to evaluate colostrum quality. However, colostrum also contains proteins and cells, which may affect immune development and future responses to vaccines. To determine the effect of maternal colostral cells on immune development, 37 female Holstein and Jersey dairy calves were bottle-fed 4 quarts total of whole colostrum (WC) or cell-free colostrum (CFC) at birth. Calves were vaccinated with 2 series of multivalent vaccines. Series A consisted of vaccines given between 1 and 4mo of life. Series B consisted of vaccines given between 5 and 10mo of life. Calf peripheral blood samples were obtained before each vaccination series and monthly for 3mo after each vaccination series. Cellular blood parameters were determined by flow cytometry. Quantitative real-time PCR was used to determine cytokine gene expression in peripheral blood mononuclear cells before vaccination series B and once a month for 2mo after vaccination series B. Calves fed CFC had fewer numbers of B cells in mo 2 after vaccination series A when compared with WC-fed calves. Calves fed CFC had decreased gene expression levels of IL-2 in mo 1 and numbers of CD4(+)CD62L(+)CD45RO(-) and CD4(+)CD62L(+)CD45RO(+) T cells in mo 0 and 1 after vaccination series B as compared with WC-fed calves. Our findings indicate a greater response to vaccines up to 6 to 10mo post-WC feeding when compared with CFC. These data suggest that adoptive transfer of maternal colostral cells at birth has a long-term effect on development of the neonatal immune system.

Implications of Lymphatic Transport to Lymph Nodes in Immunity and Immunotherapy

Adaptive immune response consists of many highly regulated, multistep cascades that protect against infection while preserving the health of autologous tissue. The proper initiation, maintenance, and resolution of such responses require the precise coordination of molecular and cellular signaling over multiple time and length scales orchestrated by lymphatic transport. In order to investigate these functions and manipulate them for therapy, a comprehensive understanding of how lymphatics influence immune physiology is needed. This review presents the current mechanistic understanding of the role of the lymphatic vasculature in regulating biomolecule and cellular transport from the interstitium, peripheral tissue immune surveillance, the lymph node stroma and microvasculature, and circulating lymphocyte homing to lymph nodes. This review also discusses the ramifications of lymphatic transport in immunity as well as tolerance and concludes with examples of how lymphatic-mediated targeting of lymph nodes has been exploited for immunotherapy applications.

L-selectin Is Essential for Delivery of Activated CD8(+) T Cells to Virus-Infected Organs for Protective Immunity

Cytotoxic CD8⁺ T lymphocytes play a critical role in the host response to infection by viruses. The ability to secrete cytotoxic chemicals and cytokines is considered pivotal for eliminating virus. Of equal importance is how effector CD8⁺ T cells home to virus-infected tissues. L-selectin has not been considered important for effector T cell homing, because levels are low on activated T cells. We report here that, although L-selectin expression is downregulated following T cell priming in lymph nodes, L-selectin is re-expressed on activated CD8⁺ T cells entering the bloodstream, and recruitment of activated CD8⁺ T cells from the bloodstream into virus-infected tissues is L-selectin dependent. Furthermore, L-selectin on effector CD8⁺ T cells confers protective immunity to two evolutionally distinct viruses, vaccinia and influenza, which infect mucosal and visceral organs, respectively. These results connect homing and a function of virus-specific CD8⁺ T cells to a single molecule, L-selectin.

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L-selectin is re-expressed on activated CD8⁺ T cells exiting lymph nodes

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L-selectin does not regulate priming, differentiation, or function of cytotoxic T lymphocytes

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Entry of activated CD8⁺ T cells into virus-infected tissues is L-selectin dependent

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The level of cell-surface L-selectin determines the extent of anti-viral immunity

Myosin-IIA regulates leukemia engraftment and brain infiltration in a mouse model of acute lymphoblastic leukemia

Leukemia dissemination (the spread of leukemia cells from the bone marrow) and relapse are associated with poor prognosis. Often, relapse occurs in peripheral organs, such as the CNS, which acts as a sanctuary site for leukemia cells to escape anti-cancer treatments. Similar to normal leukocyte migration, leukemia dissemination entails migration of cells from the blood circulation into tissues by extravasation. To extravasate, leukemia cells cross through vascular endothelial walls via a process called transendothelial migration, which requires cytoskeletal remodeling. However, the specific molecular players in leukemia extravasation are not fully known. We examined the role of myosin-IIA a cytoskeletal class II myosin motor protein, in leukemia progression and dissemination into the CNS by use of a mouse model of Bcr-Abl-driven B cell acute lymphoblastic leukemia. Small hairpin RNA-mediated depletion of myosin-IIA did not affect apoptosis or the growth rate of B cell acute lymphoblastic leukemia cells. However, in an in vivo leukemia transfer model, myosin-IIA depletion slowed leukemia progression and prolonged survival, in part, by reducing the ability of B cell acute lymphoblastic leukemia cells to engraft efficiently. Finally, myosin-IIA inhibition, either by small hairpin RNA depletion or chemical inhibition by blebbistatin, drastically reduced CNS infiltration of leukemia cells. The effects on leukemia cell entry into tissues were mostly a result of the requirement for myosin-IIA to enable leukemia cells to complete the transendothelial migration process during extravasation. Overall, our data implicate myosin-IIA as a key mediator of leukemia cell migration, making it a promising target to inhibit leukemia dissemination in vivo and potentially reduce leukemia relapses.

Leukocytes Crossing the Endothelium: A Matter of Communication

Leukocytes cross the endothelial vessel wall in a process called transendothelial migration (TEM). The purpose of leukocyte TEM is to clear the causing agents of inflammation in underlying tissues, for example, bacteria and viruses. During TEM, endothelial cells initiate signals that attract and guide leukocytes to sites of tissue damage. Leukocytes react by attaching to these sites and signal their readiness to move back to endothelial cells. Endothelial cells in turn respond by facilitating the passage of leukocytes while retaining overall integrity. In this review, we present recent findings in the field and we have endeavored to synthesize a coherent picture of the intricate interplay between endothelial cells and leukocytes during TEM.