Murine Lymphoid Tissues Research Articles

Spatially resolved quantification of oxygen consumption rate in ex vivo lymph node slices.

Cellular metabolism has been closely linked to activation state in cells of the immune system, and the oxygen consumption rate (OCR) in particular serves as a valuable metric for assessing metabolic activity. Several oxygen sensing assays have been reported for cells in standard culture conditions. However, none have provided a spatially resolved, optical measurement of local oxygen consumption in intact tissue samples, making it challenging to understand regional dynamics of consumption. Therefore, here we established a system to monitor the rates of oxygen consumption in ex vivo tissue slices, using murine lymphoid tissue as a case study. By integrating an optical oxygen sensor into a sealed perfusion chamber and incorporating appropriate correction for photobleaching of the sensor and of tissue autofluorescence, we were able to visualize and quantify rates of oxygen consumption in tissue. This method revealed for the first time that the rate of oxygen consumption in naïve lymphoid tissue was higher in the T cell region compared to the B cell and cortical regions. To validate the method, we measured OCR in the T cell regions of naïve lymph node slices using the optical assay and estimated the consumption rate per cell. The predictions from the optical assay were similar to reported values and were not significantly different from those of the Seahorse metabolic assay, a gold standard method for measuring OCR in cell suspensions. Finally, we used this method to quantify the rate of onset of tissue hypoxia for lymph node slices cultured in a sealed chamber and showed that continuous perfusion was sufficient to maintain oxygenation. In summary, this work establishes a method to monitor oxygen consumption with regional resolution in intact tissue explants, suitable for future use to compare tissue culture conditions and responses to stimulation.

OMIP-095: 40-Color spectral flow cytometry delineates all major leukocyte populations in murine lymphoid tissues.

High-dimensional immunoprofiling is essential for studying host response to immunotherapy, infection, and disease in murine model systems. However, the difficulty of multiparameter panel design combined with a lack of existing murine tools has prevented the comprehensive study of all major leukocyte phenotypes in a single assay. Herein, we present a 40-color flow cytometry panel for deep immunophenotyping of murine lymphoid tissues, including the spleen, blood, Peyer's patches, inguinal lymph nodes, bone marrow, and thymus. This panel uses a robust set of surface markers capable of differentiating leukocyte subsets without the use of intracellular staining, thus allowing for the use of cells in downstream functional experiments or multiomic analyses. Our panel classifies T cells, B cells, natural killer cells, innate lymphoid cells, monocytes, macrophages, dendritic cells, basophils, neutrophils, eosinophils, progenitors, and their functional subsets by using a series of co-stimulatory, checkpoint, activation, migration, and maturation markers. This tool has a multitude of systems immunology applications ranging from serial monitoring of circulating blood signatures to complex endpoint analysis, especially in pre-clinical settings where treatments can modulate leukocyte abundance and/or function. Ultimately, this 40-color panel resolves a diverse array of immune cells on the axes of time, tissue, and treatment, filling the niche for a modern tool dedicated to murine immunophenotyping.

Single-cell transcriptomics of Treg reveals hallmarks and trajectories of immunological aging.

Age-related immunosenescence is characterized by progressive dysfunction of adaptive immune response and increased autoimmunity. Nevertheless, the impact of aging on CD4+ regulatory T cells that are master regulators of the immune system remains largely unclear. Here, we report cellular and molecular hallmarks of regulatory T cells derived from murine lymphoid and adipose tissues at 3, 18, and 24 mo of age, respectively, by analyzing their heterogeneity that displays dynamic changes in transcriptomic effector signatures at a single-cell resolution. Although the proportion of regulatory T cells among total Cd4+ T cells, as well as their expression levels of Foxp3, did not show any global change with time, we have identified 6 transcriptomically distinct clusters of regulatory T cells with cross-tissue conserved hallmarks of aging, including increased numbers of proinflammatory regulatory T cells, reduced precursor cells, increased immature and mature T follicular regulatory cells potentially supported by a metabolic switch from oxidative phosphorylation to glycolysis, a gradual loss of CD150hi regulatory T cells that support hematopoiesis, and increased adipose tissue-specific regulatory T cells that are associated with metabolic disease. To dissect the impact of immunosenescence on humoral immunity, we propose some potential mechanisms underlying T follicular regulatory cell-mediated dysfunction by interactome analysis on T follicular regulatory cells, T follicular helper cells, and B cells during aging. Lastly, spatiotemporal analysis further revealed trajectories of regulatory T-cell aging that demonstrate the most significant changes in marrow and adipose tissues that might contribute to the development of age-related immunosenescence and type 2 diabetes. Taken together, our findings could provide a better understanding of age-associated regulatory T-cell heterogeneity in lymphoid and adipose tissues, as well as regulatory T-cell hallmarks during progressive adaptation to aging that could be therapeutically targeted for rejuvenating the aging immune system in the future.

Development of an Ultrahigh-plex Antibody Panel for Spatial Phenotyping of Murine Cancer Models

Abstract Single cell spatial phenotyping of protein biomarkers is an established tool for cancer researchers aiming to understand the biology of the tumor microenvironment. This technology has been developed around human tissues and there remains a paucity of applications available to study murine cancer models. Yet, mouse models are widely used for immuno-oncology (IO) research, justifying the development of spatial phenotyping applications for use in mice. We developed a >30-plex mouse IO antibody panel by selecting biomarkers for tumor, immune cell lineages, immune activation and checkpoints, as well as proliferation and structural markers. Purified antibodies, previously IHC validated in mouse models using rigorous protocols developed by Cell Signaling Technology (CST), were then conjugated to PhenoCycler barcodes, using a standardized conjugation protocol, and confirmed to show positive staining. We then performed ultrahigh-plex imaging using this IO antibody panel on the PhenoCycler-Fusion Platform, using murine lymphoid organs and/or tumor tissues. The resulting data were analyzed for cellular phenotypic compositions as well as the presence of cellular neighborhoods. The work presented here demonstrates the feasibility of conducting ultrahigh-plex spatial phenotyping in FFPE mouse tissues. The tools that were developed as part of this study can readily be deployed for discovery and translational research and will engender future comparative mouse and human spatial phenotyping studies that can further our understanding of cancer biology.

Modeling relationship of pharmacokinetics, in vitro potency, and α4β7 receptor occupancy with intestinal cell trafficking in a gut-homing mouse model of IBD with MORF-057

Abstract Objective: MORF-057 is an orally bioavailable, selective, and potent small molecule inhibitor of α4β7 integrin being developed for inflammatory bowel diseases (IBD) that is currently in phase 1 clinical testing. We have previously presented work that characterized its nonclinical pharmacologic profile. The current study integrates data to generate a pharmacokinetic (PK) and pharmacodynamic (PD) model of MORF-057. Methods: To determine in vivo potency, MORF-057 was tested in murine gut homing assays and the PD response was determined relative to the non-protein bound drug in mouse plasma. A cell adhesion assay (CAA) for α4β7 was refined to enable detection of picomolar-level sensitivity. Murine receptor occupancy (RO) assays for α4β7 and α4β1 were established under physiologic conditions, and MORF-057 was evaluated for its potency and selectivity in fresh mouse whole blood. These datasets were used to build and validate predictive models of PD response. Results: MORF-057 strongly inhibited the homing of α4β7hi cells to murine gut lymphoid tissues with an IC90 of 7.9 nM. MORF-057 showed high potency in CAA with an IC90 of 8.8 nM. Similarly, RO assays confirmed MORF-057 to be a highly potent inhibitor of α4β7 in mouse whole blood with an IC90 of 20.5 nM and over 1500-fold selectivity vs. α4β1. The predictive models built upon these datasets revealed a strong PK-PD relationship of α4β7 inhibitors in vivo. Conclusions: We observed consistently high potency of MORF-057 across multiple assay platforms. Integrated modeling based on these assays, particularly the RO assay, successfully predicted the PD response to MORF-057. These data begin to establish the relationship between PK, target engagement, and PD with MORF-057.

Optimized Protocol for Isolation of Small Extracellular Vesicles from Human and Murine Lymphoid Tissues.

Small extracellular vesicles (sEVs) are nanoparticles responsible for cell-to-cell communication released by healthy and cancer cells. Different roles have been described for sEVs in physiological and pathological contexts, including acceleration of tissue regeneration, modulation of tumor microenvironment, or premetastatic niche formation, and they are discussed as promising biomarkers for diagnosis and prognosis in body fluids. Although efforts have been made to standardize techniques for isolation and characterization of sEVs, current protocols often result in co-isolation of soluble protein or lipid complexes and of other extracellular vesicles. The risk of contaminated preparations is particularly high when isolating sEVs from tissues. As a consequence, the interpretation of data aiming at understanding the functional role of sEVs remains challenging and inconsistent. Here, we report an optimized protocol for isolation of sEVs from human and murine lymphoid tissues. sEVs from freshly resected human lymph nodes and murine spleens were isolated comparing two different approaches—(1) ultracentrifugation on a sucrose density cushion and (2) combined ultracentrifugation with size-exclusion chromatography. The purity of sEV preparations was analyzed using state-of-the-art techniques, including immunoblots, nanoparticle tracking analysis, and electron microscopy. Our results clearly demonstrate the superiority of size-exclusion chromatography, which resulted in a higher yield and purity of sEVs, and we show that their functionality alters significantly between the two isolation protocols.

Probody Therapeutic Design of 89Zr-CX-072 Promotes Accumulation in PD-L1-Expressing Tumors Compared to Normal Murine Lymphoid Tissue.

Probody therapeutic CX-072 is a protease-activatable antibody that is cross-reactive with murine and human programmed death-ligand 1 (PD-L1). CX-072 can be activated in vivo by proteases present in the tumor microenvironment, thereby potentially reducing peripheral, anti-PD-L1-mediated toxicities. To study its targeting of PD-L1-expressing tissues, we radiolabeled CX-072 with the PET isotope zirconium-89 (89Zr). 89Zr-labeled CX-072, nonspecific Probody control molecule (PbCtrl) and CX-072 parental antibody (CX-075) were injected in BALB/c nude mice bearing human MDA-MB-231 tumors or C57BL/6J mice bearing syngeneic MC38 tumors. Mice underwent serial PET imaging 1, 3, and 6 days after intravenous injection (pi), followed by ex vivo biodistribution. Intratumoral 89Zr-CX-072 distribution was studied by autoradiography on tumor tissue sections, which were subsequently stained for PD-L1 by IHC. Activated CX-072 species in tissue lysates were detected by Western capillary electrophoresis. PET imaging revealed 89Zr-CX-072 accumulation in MDA-MB-231 tumors with 2.1-fold higher tumor-to-blood ratios at 6 days pi compared with 89Zr-PbCtrl. Tumor tissue autoradiography showed high 89Zr-CX-072 uptake in high PD-L1-expressing regions. Activated CX-072 species were detected in these tumors, with 5.3-fold lower levels found in the spleen. Furthermore, 89Zr-CX-072 uptake by lymphoid tissues of immune-competent mice bearing MC38 tumors was low compared with 89Zr-CX-075, which lacks the Probody design. 89Zr-CX-072 accumulates specifically in PD-L1-expressing tumors with limited uptake in murine peripheral lymphoid tissues. Our data may enable clinical evaluation of 89Zr-CX-072 whole-body distribution as a tool to support CX-072 drug development (NCT03013491).

Beta cell-specific CD8+ T cells maintain stem cell memory-associated epigenetic programs during type 1 diabetes.

The pool of beta cell-specific CD8+ T-cells in type 1 diabetes (T1D) sustains an autoreactive potential despite having access to a constant source of antigen. To investigate the long-lived nature of these cells, we established a DNA methylation-based T cell “multipotency index” and found that beta cell-specific CD8+ T-cells retained a stem-like epigenetic multipotency score. Single cell ATAC-seq analysis confirmed the co-existence of naive and effector-associated epigenetic programs in individual beta cell-specific CD8+ T-cells. Assessment of beta cell-specific CD8+ T-cell anatomical distribution and the establishment of stem-associated epigenetic programs revealed that self-reactive CD8+ T-cells isolated from murine lymphoid tissue retained developmentally plastic phenotypic and epigenetic profiles relative to the same cells isolated from the pancreas. Collectively, these data provide new insight into the longevity of beta cell-specific CD8+ T cell responses, and document the utility of this novel methylation-based multipotency index for investigating human and mouse CD8+ T-cell differentiation.

Targeting Interleukin(IL)-30/IL-27p28 signaling in cancer stem-like cells and host environment synergistically inhibits prostate cancer growth and improves survival

BackgroundInterleukin(IL)-30/IL-27p28 production by Prostate Cancer (PC) Stem-Like Cells (SLCs) has proven, in murine models, to be critical to tumor onset and progression. In PC patients, IL-30 expression by leukocytes infiltrating PC and draining lymph nodes correlates with advanced disease grade and stage. Here, we set out to dissect the role of host immune cell-derived IL-30 in PC growth and patient outcome.MethodsPC-SLCs were implanted in wild type (WT) and IL-30 conditional knockout (IL-30KO) mice. Histopathological and cytofluorimetric analyses of murine tumors and lymphoid tissues prompted analyses of patients’ PC samples and follow-ups.ResultsImplantation of PC-SLCs in IL-30KO mice, gave rise to slow growing tumors characterized by apoptotic events associated with CD4+T lymphocyte infiltrates and lack of CD4+Foxp3+ T regulatory cells (Tregs). IL-30 knockdown in PC-SLCs reduced cancer cell proliferation, vascularization and intra-tumoral Indoleamine 2,3-Dioxygenase (IDO)+CD11b+Gr-1+ myeloid-derived cells (MDCs) and led to a significant delay in tumor growth and increase in survival. IL-30-silenced tumors developed in IL-30KO mice, IL-30−/−tumors, lacked vascular supply and displayed frequent apoptotic cancer cells entrapped by perforin+TRAIL+CD3+Tlymphocytes, most of which had a CD4+T phenotype, whereas IL-10+TGFβ+Foxp3+Tregs were lacking. IL-30 silencing in PC-SLCs prevented lung metastasis in 73% of tumor-bearing WT mice and up to 80% in tumor-bearing IL-30KO mice.In patients with high-grade and locally advanced PC, those with IL-30−/−tumors, showed distinct intra-tumoral cytotoxic granule-associated RNA binding protein (TIA-1)+CD4+Tlymphocyte infiltrate, rare Foxp3+Tregs and a lower biochemical recurrence rate compared to patients with IL-30+/+tumors in which IL-30 is expressed in both tumor cells and infiltrating leukocytes.ConclusionThe lack of host leukocyte-derived IL-30 inhibits Tregs expansion, promotes intra-tumoral infiltration of CD4+T lymphocytes and cancer cell apoptosis. Concomitant lack of MDC influx, obtained by IL-30 silencing in PC-SLCs, boosts cytotoxic T lymphocyte activation and cancer cell apoptosis resulting in a synergistic tumor suppression with the prospective benefit of better survival for patients with advanced disease.

8O - 89Zr-labeled anti-PD-L1 CX-072 PET imaging in human xenograft and syngeneic tumors

Background: Immune checkpoint inhibiting antibodies have antitumor activity across several tumor types, but can also elicit immune-mediated adverse events (imAEs). CX-072 is an investigational antibody prodrug (Probody™ therapeutic), reactive to the murine and human programmed death-ligand 1 (PD-L1) immune checkpoint. CX-072 can be activated to a fully avid antibody by tumor-associated proteases that remove the masking peptides blocking the antigen-binding domain, which may limit peripheral PD-L1 binding and therefore imAEs. CX-072 was radiolabeled with zirconium-89 (89Zr) to study its biodistribution and tumor- versus lymphoid tissue-targeting properties using positron emission tomography (PET). Methods: CX-072, non-specific Probody™ therapeutic control (PbCtrl) and CX-072 parental antibody (CX-075) were radiolabeled with 89Zr. Human PD-L1-expressing MDA-MB-231 tumor-bearing BALB/c nude mice received 10 μg 89Zr-CX-072, 89Zr-PbCtrl or 89Zr-CX-075 (∼5 MBq) supplemented with 0, 40 or 240 µg of respective unlabeled antibody. Biodistribution was also evaluated in C57BL6/J mice bearing PD-L1-expressing MC38 syngeneic colon adenoma tumors. Mice underwent PET scans 1, 3 and 6 days post intravenous injection (pi), followed by ex vivo analysis. Results: In MDA-MB-231 tumors, 89Zr-CX-072 and 89Zr-CX-075 showed comparable uptake of 8.7 ± 1.0%ID/g and 8.8 ± 2.9%ID/g respectively for the 10 µg total protein dose, which is 2.3-fold higher compared to 89Zr-PbCtrl. Autoradiography showed 89Zr-CX-072 localization in PD-L1-positive tumor tissue areas on immunohistochemistry. Activated CX-072 was detected by capillary electrophoresis immunoassay mainly in MDA-MB-231 tumor, with limited amounts found in spleen. Flow cytometry confirmed PD-L1 expression in lymphoid tissues of C57BL6/J mice, while 89Zr-CX-072 uptake in these tissues was similar to 89Zr-PbCtrl and significantly lower compared to 89Zr-CX-075. Conclusions:89Zr-CX-072 accumulates in PD-L1-expressing tumors with minor uptake in murine peripheral lymphoid tissues, confirming that the CX-072 structure limits uptake in non-tumor, PD-L1-expressing tissues. We developed clinical grade 89Zr-CX-072 to study its whole-body distribution in patients. Legal entity responsible for the study: Dept. of Medical Oncology, University Medical Center Groningen (UMCG), The Netherlands. Funding: CytomX Therapeutics Inc. Disclosure: I. Popova, B. Howng, O. Vasiljeva: Employee: CytomX Therapeutics Inc. E.G.E. de Vries: Research funding: CytomX was made available to her institution (UMCG); Advisory boards: Pfizer, Daiichi Sankyo; Other funding: Amgen, Bayer, Chugai, G1 Therapeutics, Genentech/Roche, Nordic Nanovector, Regeneron, Synthon, all payments to UMCG. All other authors have declared no conflicts of interest.

Sleep restriction alters the temporal expression of major histocompatibility complex class II molecules in murine lymphoid tissues

Inadequate sleep is a major health concern of modern societies in view of the increased morbidity and mortality rates from physiological disturbances, including compromised adaptive immune responses. Many studies investigated the effect sleep restriction (SR) on the normal immune response in terms of leukocyte number and circulating cytokine and T helper cell (Th) profiles, but none considered the major histocompatibility complex (MHC), namely class II molecules. As no information exists about the normal temporal expression of MHC class II, the present study aimed at understanding how SR affects the adaptive immune response via altering the 1) normal daily expression profile and 2) overall constitutive levels of murine MHC class II by leukocytes’ isolates from spleen and axillary lymph nodes. Male C57BL/6 mice were acclimatized to 12:12 light/dark cycle (lights on at 0700, corresponding to Zeitgeber time (ZT) 0) for a week before splitting into 2 groups: control (C) and SR (exposed to a 12 and 18 h of activity, respectively). SR was carried for one week before lymphoid tissues from both C and SR mice were sampled at the following time points: ZT0, ZT5, ZT10, ZT13, and ZT18. Spleen and lymph node cells were assessed for leukocyte number and MHC class II expression at the preselected time points using flow cytometry. SR resulted in a 21% decrease in granulocyte and 24% increase in agranulocyte numbers. MHC class II expression in both lymphoid tissues of C mice varied synchronously across the preselected times of day; they were relatively high just prior to activity onset and later in this period. Comparatively, the diurnal protein profile was altered in both lymphoid tissues of SR: 1) the rise of MHC class II expression during the rest period occurred 4–5 hours earlier and 2) the cyclical pattern during the activity period was blunted and protein expression was maintained at relatively high levels. MHC class II expression was higher in the lymph nodes and lower in the spleen of SR than C, though these differences did not reach statistical significance. In SR; however, the average protein level was significantly higher in lymph nodes than spleen (376.0 + 184.9 vs 188.6 + 42.2, respectively; p = .002) and higher in the granulocytes relative to agranulocytes. Our findings provide empirical evidence of a constitutive diurnal expression pattern for MHC class II molecules that is prone to upregulation upon SR, namely in lymph nodes, and specifically expressed by granulocytes. We speculate that, in mice, chronic sleep deprivation would further dysregulate MHC class II expression that might result in aberrant T cell activation with probable immune-associated pathological diseases such as allergies, autoimmunity, and tumors.

Immunophenotyping of Tissue Samples Using Multicolor Flow Cytometry.

Flow cytometry enables the measurement of single cells in a flowing system. Heterogeneous mixtures of cells or particles can be analyzed with respect to their morphology, surface and intracellular protein expression, DNA content, and cellular physiology at high speed and purity. A series of key technical developments and improvements in flow cytometry hardware, software, and dye chemistry made it possible to measure more than 20 parameters simultaneously. Here, we provide a stepwise protocol for the preparation of single cell suspension samples from different murine lymphoid or tumor tissues and a detailed description of a 17-color polychromatic flow cytometry analysis of tumor-infiltrating leukocytes.

Isolation and Characterization of Mouse and Human Follicular Dendritic Cells.

Follicular dendritic cells (FDCs) reside in the B cell follicles of secondary and tertiary lymphoid tissues where they play key roles in the development and maintenance of lymphoid tissue architecture and function. FDCs trap native antigens for extended periods of time in the form of immune complexes which critcally regulate germinal center reactions in health and disease. Here, we describe how to isolate and characterize FDCs from murine and human lymphoid tissues.

A Stromal Cell Niche for Human and Mouse Type 3 Innate Lymphoid Cells.

Adaptive immunity critically depends on the functional compartmentalization of secondary lymphoid organs. Mesenchymal stromal cells create and maintain specialized niches that support survival, activation, and expansion of T and B cells, and integrated analysis of lymphocytes and their niche has been instrumental in understanding adaptive immunity. Lymphoid organs are also home to type 3 innate lymphoid cells (ILC3), innate effector cells essential for barrier immunity. However, a specialized stromal niche for ILC3 has not been identified. A novel lineage-tracing approach now identifies a subset of murine fetal lymphoid tissue organizer cells that gives rise exclusively to adult marginal reticular cells. Moreover, both cell types are conserved from mice to humans and colocalize with ILC3 in secondary lymphoid tissues throughout life. In sum, we provide evidence that fetal stromal organizers give rise to adult marginal reticular cells and form a dedicated stromal niche for innate ILC3 in adaptive lymphoid organs.

MicroRNA 142-3p attenuates spread of replicating retroviral vector in hematopoietic lineage-derived cells while maintaining an antiviral immune response.

We are developing a retroviral replicating vector (RRV) encoding cytosine deaminase as an anticancer agent for gliomas. Despite its demonstrated natural selectivity for tumors, and other safety features, such a virus could potentially cause off-target effects by productively infecting healthy tissues. Here, we investigated whether incorporation of a hematopoietic lineage-specific microRNA target sequence in RRV further restricts replication in hematopoietic lineage-derived human cells in vitro and in murine lymphoid tissues in vivo. One or four copies of a sequence perfectly complementary to the guide strand of microRNA 142-3p were inserted into the 3' untranslated region of the RRV genome expressing the transgene encoding green fluorescent protein (GFP). Viral spread and GFP expression of these vectors in hematopoietic lineage cells in vitro and in vivo were measured by qPCR, qRT-PCR, and flow cytometry. In hematopoietic lineage-derived human cell lines and primary human stimulated peripheral blood mononuclear cells, vectors carrying the 142-3pT sequence showed a remarkable decrease in GFP expression relative to the parental vector, and viral spread was not observed over time. In a syngeneic subcutaneous mouse tumor model, RRVs with and without the 142-3pT sequences spread equally well in tumor cells; were strongly repressed in blood, bone marrow, and spleen; and generated antiviral immune responses. In an immune-deficient mouse model, RRVs with 142-3pT sequences were strongly repressed in blood, bone marrow, and spleen compared with unmodified RRV. Tissue-specific microRNA-based selective attenuation of RRV replication can maintain antiviral immunity, and if needed, provide an additional safeguard to this delivery platform for gene therapy applications.

Role of Murine Intestinal Interleukin-1 Receptor 1-Expressing Lymphoid Tissue Inducer-Like Cells in Salmonella Infection

Interleukin (IL)-1 signaling plays a critical role in intestinal immunology. Here, we report that the major population of intestinal lamina propria lymphocytes expressing IL-1 receptor 1 (IL-1R1) is the lymphoid tissue inducer (LTi)-like cell, a type of innate lymphoid cell. These cells are significant producers of IL-22, and this IL-22 production depends on IL-1R1 signaling. LTi-like cells are required for defense against Salmonella enterica serovar Typhimurium. Moreover, colonic LTi-like cell numbers depend on the presence of the intestinal microbiota. LTi-like cells require IL-1R1 for production of protective cytokines and confer protection in infectious colitis, and their cell numbers in the colon depend upon having a microbiome.

CD117+CD3−CD56−OX40Lhigh cells express IL‐22 and display an LTi phenotype in human secondary lymphoid tissues

Here, we identify cells within human adult secondary lymphoid tissues that are comparable in phenotype and location to the lymphoid tissue inducer (LTi) cells that persist in the adult mouse. Identified as CD117(+) CD3(-) CD56(-) cells, like murine LTi cells, they lack expression of many common lineage markers and express CD127, OX40L and TRANCE. These cells were detected at the interface between the B- and T- zones, as well as at the subcapsular sinus in LNs, the location where LTi cells reside in murine spleen and LNs. Furthermore, like murine LTi cells, these cells expressed high levels of IL-22 and upregulated IL-22 expression upon IL-23 stimulation. Importantly, these cells were not an NK cell subset since they showed no expression of IFN-γ and perforin. Interestingly, a subset of the CD117(+) CD3(-) CD56(-) OX40L(+) population expressed NKp46, again similar to recent findings in mice. Finally, these cells supported memory CD4(+) T-cell survival in an OX40L-dependent manner. Combined, these data indicate that the CD117(+) CD3(-) CD56(-) OX40L(+) cells in human secondary lymphoid tissues are comparable in phenotype, location and function to the LTi cells that persist within adult murine secondary lymphoid tissues.

Dendritic Cells Produce CXCL13 and Participate in the Development of Murine Small Intestine Lymphoid Tissues

In the adult intestine, luminal microbiota induce cryptopatches to transform into isolated lymphoid follicles (ILFs), which subsequently act as sites for the generation of IgA responses. The events leading to this conversion are incompletely understood. Dendritic cells (DCs) are components of cryptopatches (CPs) and ILFs and were therefore evaluated in this process. We observed that the adult murine intestine contains clusters of DCs restricted to the CP/ILF continuum. A numerical and cell associative hierarchy in the adult intestine and a chronologic hierarchy in the neonatal intestine demonstrated that these clusters form after the coalescence of CD90+ cells to form CPs and before the influx of B220+ B lymphocytes to form ILFs. Cluster formation was dependent on lymphotoxin and the lymphotoxin beta receptor and independent of lymphocytes. The ILF DC population was distinguished from that of the lamina propria by the absence of CD4+CD11c+ cells and an increased proportion of CD11c+B220+ cells. The formation of clusters was not limited by DC numbers but was induced by luminal microbiota. Moreover, in the absence of the chemokine CXCL13, CP transformation into ILF was arrested. Furthermore, ILF DCs express CXCL13, and depletion of DCs resulted in regression of ILFs and disorganization of CPs. These results reveal DC participation in ILF transformation and maintenance and suggest that in part this may be due to CXCL13 production by these cells.

In vitro preactivated human T cells engraft in SCID mice and migrate to murine lymphoid tissues.

Mice with severe combined immunodeficiency (SCID) accept grafts of human T and B lymphocytes derived from resting peripheral blood mononuclear cells (PBMC). We wished to determine whether activated human T cells engraft and migrate into lymphoid tissues in SCID mice. PBMC (50 x 10(6)) activated in vitro in a 4-day mixed lymphocyte culture (MLC) were injected into the peritoneum of 12 SCID mice. In 11 of 12 animals killed at 3 or 4 weeks after injection, human cells were detected in cells pooled from lymphoid organs by flow cytometry and by immunohistochemical staining of frozen tissue sections. The percentage of CD45+ cells in the 11 mice ranged from 2% to 45% and the absolute numbers of CD45+ cells recovered from lymphoid organs ranged from 4 x 10(6) to 90 x 10(6). Up to 93% of the human cells expressed the CD3 antigen together with either CD4 or CD8. Human T cells were localized in periarteriolar areas in murine spleens, whereas in the lymph nodes and gut mucosa, the T cells did not show the pattern for T-dependent areas found in human lymphoid tissue. Numerous human plasma cells were detected in the spleen and gut mucosal crypts of engrafted SCID mice. Human IgG was detected in the serum of all 11 engrafted SCID mice. The functional activity of human T cells recovered from murine splenic tissue was very low 3-4 weeks after engraftment.

Identification of the immediate precursors of tumor dendritic cells

The ontogeny of dendritic cells (DC) in tumors remains unclear. Our previous studies have shown that conventional DC (cDC) in murine lymphoid tissue and bone marrow arise from a distinct population of CD11c(+) MHC class II(−)lineage(−) immediate precursors, which are now known as pre‐cDC. In this study, we show that pre‐cDC are a key source of DC in experimental murine tumors. Pre‐cDC from tumors are replication‐competent and generate homogeneous cDC that continue to divide for several generations when co‐cultured on a supportive stromal monolayer. Adoptively transferred pre‐cDC, but not monocytes, generate DC in tumors. In vivo bromodeoxyuridine incorporation studies reveal that endogenous pre‐cDC and cDC are actively replicating in tumors. The chemokine, CCL3, was found to play a critical role in promoting pre‐cDC migration into tumors from the circulation. Collectively, our findings provide evidence of a distinct development pathway for cDC in tumors and highlight the importance of in situ replication of pre‐cDC and cDC in their expansion. The identification of this pathway is an important step in addressing how tumor microenvironments influence the developmental fate and function of DC.