Dendritic cell subsets in lymph nodes are characterized by the specific draining area and influence the phenotype and fate of primed T cells

Control of intestinal inflammation by glycosylation-dependent lectin-driven immunoregulatory circuits

Diverse immunoregulatory circuits operate to preserve intestinal homeostasis and prevent inflammation. Galectin-1 (Gal1), a β-galactoside-binding protein, promotes homeostasis by reprogramming innate and adaptive immunity. Here, we identify a glycosylation-dependent "on-off" circuit driven by Gal1 and its glycosylated ligands that controls intestinal immunopathology by targeting activated CD8⁺ T cells and shaping the cytokine profile. In patients with inflammatory bowel disease (IBD), augmented Gal1 was associated with dysregulated expression of core 2 β6-N-acetylglucosaminyltransferase 1 (C2GNT1) and α(2,6)-sialyltransferase 1 (ST6GAL1), glycosyltransferases responsible for creating or masking Gal1 ligands. Mice lacking Gal1 exhibited exacerbated colitis and augmented mucosal CD8⁺ T cell activation in response to 2,4,6-trinitrobenzenesulfonic acid; this phenotype was partially ameliorated by treatment with recombinant Gal1. While C2gnt1^-/- mice exhibited aggravated colitis, St6gal1^-/- mice showed attenuated inflammation. These effects were associated with intrinsic T cell glycosylation. Thus, Gal1 and its glycosylated ligands act to preserve intestinal homeostasis by recalibrating T cell immunity.

Mannose-Modified Serum Exosomes for the Elevated Uptake to Murine Dendritic Cells and Lymphatic Accumulation

The surface of bovine serum-derived exosomes (EXOs) are modified with α-d-mannose for facile interaction with mannose receptors on dendritic cells (DCs) and for efficient delivery of immune stimulators to the DCs. The surface of the EXOs is modified with polyethylene glycol (PEG) without particle aggregation (≈50 nm) via the incorporation of 1,2-distearoyl-sn-glycero-3-phosphoethanolamine (DSPE) into the lipid layer of the EXO, compared to chemical conjugation by N-hydroxysuccinimide activated PEG (NHS-PEG). PEG modification onto the exosomal surface significantly decreases the non-specific cellular uptake of the EXOs into the DCs. However, the EXOs with mannose-conjugated PEG-DSPE (EXO-PEG-man) exhibit excellent intracellular uptake into the DCs and boost the immune response by the incorporation of adjuvant, monophosphoryl lipid A (MPLA) within the EXO. After an intradermal injection, a higher retention of EXO-PEG-man is observed in the lymph nodes, which could be used for the efficient delivery of immune stimulators and antigens to the lymph nodes in vivo.

Characterization and expression of DEC205 in the cDC1 and cDC2 subsets of porcine dendritic cells from spleen, tonsil, and submaxillary and mesenteric lymph nodes

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This study describes the characterization of cDCs, cDC1 and cDC2 in porcine lymphoid tissues.

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Results show that the spleen had the highest frequency of cDCs.

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The cDC1:cDC2 ratio showed a predominant presence of cDC1 in all lymphoid tissues.

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DEC205 was expressed on cDC1 and cDC2 cells from all analyzed tissues.

Conventional dendritic cells (cDCs) are divided into the following different subtypes: cDC1, which promotes a Th1 response, and cDC2, which stimulates a Th2 and Th17 response. These cells have not been characterized in porcine lymphoid tissues. DEC205 is a receptor that increases antigen presentation and allows DCs to cross-present antigens. The objectives of this work were to characterize cDCs subsets in the tonsil, submaxillary and mesenteric lymph nodes and spleen lymphoid tissues and to determine their expression of DEC205 by flow cytometry. The cDC1 (MHCII^highCADM1^highCD172a^−/low) and cDC2 (MHCII^highCADM1^highCD172a⁺) phenotypes were confirmed by the expression of characteristic cDC1 and cDC2 transcripts (FLT3, XCR1 and FCER1α). Among all lymphoid tissues, the spleen had the highest frequency of total cDCs. The cDC1:cDC2 ratio showed that all lymph tissues had higher levels of cDC1 than levels of cDC2. DEC205⁺ cDCs were found in all analyzed tissues, albeit with different frequencies. Our research will facilitate the study on the function of these cells and the investigation of the strategies for DEC205 targeting and functional studies.

Identification of Melanoma-reactive CD4+ T-Cell Subsets From Human Melanoma Draining Lymph Nodes

Our laboratory has previously demonstrated that melanoma draining lymph node (MDLN) samples from stage III patients contained both CD4 and CD8 T cells that can be readily expanded to mediate tumor cell apoptosis in vitro and improve survival in mice bearing human melanoma xenografts. In this study, we investigated whether MDLN T cells contain melanoma-reactive CD4 T-cell compartment and what they are. To test this, we performed multiparametric (11-color and 6-color) fluorescence-activated cell sorting analyses to monitor phenotypic and functional property of CD4 T cells in response to melanoma cell antigen reexposure. Our results have demonstrated that the antigen reexposure could result in a generation of CD4CCR7CD62LCD27 T-cell subsets with various effector cell-like properties. Within the CD4CCR7CD62LCD27 T-cell compartment, in response to antigen reexposure, some of the cells expressed significantly upregulated CD40L and/or CXCR5, and some of them expressed significantly upregulated interleukin-2 and/or tumor necrosis factor-α. This may suggest the existence of melanoma-reactive CD4 "effector-precursor" cells within the expanded MDLN cells and their differentiation into various effector lineages in response to antigen restimulation. Recent clinical trials have demonstrated that effective adoptive cellular immunotherapy maybe enhanced by antigen-specific CD4 T cells. Therefore, results of this study may significantly benefit innovative design of +adoptive cellular immunotherapy that can potentially mediate enhanced and durable clinical responses.

Stromal cells as trend-setters for cells migrating into the lymph node

Lymph node stromal cells are known to be immunorelevant during inflammation and tolerance. Differences between peripheral lymph nodes and mesenteric lymph nodes are important for an efficient and effective immune defense. Stromal cells were considered to be perfectly adapted to their draining area and not changeable concerning their expression pattern. Here we show that stromal cells can change their profile after isolation and transplantation into a different draining area. Subsequently, these newly organized lymph nodes are able to induce not only a region-specific but also an antigen-specific immune response. Thus, stromal cells are trend-setters for immune cells in producing a microenvironment that allows an optimized immune defense.

Enhanced stimulation of anti-ovarian cancer CD8(+) T cells by dendritic cells loaded with nanoparticle encapsulated tumor antigen

PROBLEM

Dendritic cell (DC)-based cancer therapies are favored approaches to stimulate anti-tumor T-cell responses. Unfortunately, tolerance to tumor antigens is difficult to overcome. Biodegradable poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NP) are effective reagents in the delivery of drugs and tumor-associated antigens (TAA). In this study, we assessed the capacity of a PLGA NP-based delivery system to augment CD8 T-cell responses to ovarian cancer TAA.

METHOD OF STUDY

Human DC were generated from blood monocytes by conventional in vitro differentiation and loaded with either soluble tumor lysate or NP/lysate conjugates (NPL). These antigen-loaded DC were then used to stimulate autologous CD8(+) T cells. Cytokine production and activation markers were evaluated in the CD8(+) T cells.

RESULTS

DC loading with NPL increased cytokine production by stimulated CD8 T cells and induced T-cell expression of cell surface co-stimulatory molecules, typical of anti-tumor immune responses. In contrast, delivery of naked tumor lysate antigens preferentially induced a T-cell profile characteristic of tolerization/exhaustion.

CONCLUSION

These findings indicate that delivery of TAA in NP enables DC to efficiently activate anti-tumor CD8(+) T cells. PLGA NP encapsulation of tumor-derived lysate protein antigens is an encouraging new preparative methodology for DC-based vaccination meriting clinical testing.

Lymph node transplantation and its immunological significance in animal models

Lymph nodes (LNs) are distributed all over the body and whatever the site consists of the same cell populations. However, there are great differences between LN from different draining areas. For example, in mesenteric LN, homing molecules, for example, CCR9 and α4β7 integrin, were induced and cytokines, for example, IL-4, were produced on higher levels compared to peripheral LN. To study the immunological functions of LN, LN transplantation was performed in some specific areas using different animal models. Many groups investigated not only the regeneration of transplanted LN but also the induction of immune responses or tolerance after transplantation. Existing differences between LNs were still detectable after transplantation. Most important, stromal cells of the LN were identified as responsible for these differences. They survive during regeneration and were shown to reconstruct not only the structure of the new LN but also the microenvironment.

Tissue-based class control: the other side of tolerance

In this Essay, we offer a new perspective on how immune responses are regulated. We do not cover how they are turned on and off, but focus instead on the second major aspect of an immune response: the control of effector class. Although it is generally thought that the class of an immune response is tailored to fit the invading pathogen, we suggest here that it is primarily tailored to fit the tissue in which the response occurs. To this end, we cover such topics as the nature of T helper (T(H)) cell subsets (current and yet to be discovered), the nature of privileged sites, the difference between oral tolerance and oral vaccination, why the route of immunization matters, whether the T(H)1-type response is really the immune system's primary defense, and whether there might be a different role for some regulatory T cells.

Stromal cells confer lymph node-specific properties by shaping a unique microenvironment influencing local immune responses

Lymph nodes (LN) consist not only of highly motile immune cells coming from the draining area or from the systemic circulation, but also of resident stromal cells building the backbone of the LN. These two cell types form a unique microenvironment which is important for initiating an optimal immune response. The present study asked how the unique microenvironment of the mesenteric lymph node (mLN) is influenced by highly motile cells and/or by the stromal cells. A transplantation model in rats and mice was established. After resecting the mLN, fragments of peripheral lymph node (pLN) or mLN were inserted into the mesentery. The pLN and mLN have LN-specific properties, resulting in differences of, for example, the CD103(+) dendritic cell subset, the adhesion molecule mucosal addressin cell adhesion molecule 1, the chemokine receptor CCR9, the cytokine IL-4, and the enzyme retinal dehydrogenase 2. This new model clearly showed that during regeneration stromal cells survived and immune cells were replaced. Surviving high endothelial venules retained their site-specific expression (mucosal addressin cell adhesion molecule 1). In addition, the low expression of retinal dehydrogenase 2 and CCR9 persisted in the transplanted pLN, suggesting that stromal cells influence the lymph node-specific properties. To examine the functional relevance of this different expression pattern in transplanted animals, an immune response against orally applied cholera toxin was initiated. The data showed that the IgA response against cholera toxin is significantly diminished in animals transplanted with pLN. This model documents that stromal cells of the LN are active players in shaping a unique microenvironment and influencing immune responses in the drained area.