T-cell Compartment Research Articles

The human V\u03b42+ T-cell compartment comprises distinct innate-like V\u03b39+ and adaptive V\u03b39- subsets

Vδ2+ T cells form the predominant human γδ T-cell population in peripheral blood and mediate T-cell receptor (TCR)-dependent anti-microbial and anti-tumour immunity. Here we show that the Vδ2+ compartment comprises both innate-like and adaptive subsets. Vγ9+ Vδ2+ T cells display semi-invariant TCR repertoires, featuring public Vγ9 TCR sequences equivalent in cord and adult blood. By contrast, we also identify a separate, Vγ9− Vδ2+ T-cell subset that typically has a CD27hiCCR7+CD28+IL-7Rα+ naive-like phenotype and a diverse TCR repertoire, however in response to viral infection, undergoes clonal expansion and differentiation to a CD27loCD45RA+CX3CR1+granzymeA/B+ effector phenotype. Consistent with a function in solid tissue immunosurveillance, we detect human intrahepatic Vγ9− Vδ2+ T cells featuring dominant clonal expansions and an effector phenotype. These findings redefine human γδ T-cell subsets by delineating the Vδ2+ T-cell compartment into innate-like (Vγ9+) and adaptive (Vγ9−) subsets, which have distinct functions in microbial immunosurveillance.

GM-CSF regulation of autophagy in monocytes enhances immune response to Cryptococcus gattii

Abstract Cryptococcal meningoencephalitis is responsible for over 15% of HIV-related deaths worldwide and is also the most common cause of non-viral meningitis in the US. The role of T-cells in cryptococcal disease is well studied however a significant portion of previously healthy non-HIV patients with cryptococcal meningoencephalitis have an intact CD4+ T-cell compartment. We observed that patients with GM-CSF autoantibodies have a decrease in autophagy within their classical monocyte compartment. This reduction in autophagy is correlated with an enhancement of IL-1β production, additionally GM-CSF synergizes with TLR2, TLR4, and TLR5 in the induction of IL-1β. The importance of GM-CSF inhibition of autophagy appears to be most dramatic when monocytes are in conditions of weak TLR stimulation, particularly TLR4 stimulation with LPS. The capsule for Cryptococcus gattii, the prominent species involved with cryptococcal meningoencephalitis in previously health adults, has been shown to have the ability to dampen or block surface recognition by the immune system, thus GM-CSF synergy may have a critical role for driving the immune response against C. gattii infection. In the murine model of myeloid-specific ATG5 deficiency, mice have enhanced survival to C. gattii infection. Additionally, this GM-CSF down-regulation of autophagy is independent of mTOR activity, and contingent on a cyclic AMP/CTLA4/DCP2 pathway.

Epithelial Cell Control of Adaptive Immune Plasticity in Periodontal Disease

Abstract In periodontal disease (PD), subgingival bacteria initiate and sustain a non-resolving inflammation that is ineffective at controlling the infection. T cells are critical for proper control of infection, but also homeostasis at mucosal surfaces including that of the periodontium. We have previously demonstrated that PD is associated with the local expression of cytokines associated with induction of Th(c)1/Th(c)17 plasticity, whereby loss of oral epithelial cell (OEC) MyD88-dependent-signaling results in exacerbation of this response. The objective of this study was to determine in which T-cell compartment plasticity occurs during PD and whether MyD88-dependent OEC signaling regulates this plasticity. Mice with MyD88-sufficient (B6) or MyD88-deficient (B6OEC.MyD88) OEC were subjected to oral polymicrobial infection for six weeks, after which the severity of disease as measured by alveolar bone loss and immunophenotype of the cellular infiltrate were evaluated. A temporal reduction in the frequency of Th(c)17 cells along with an increased frequency of Th(c)1 and Th(c)1/Th(c)7 cells was observed in B6 mice as PD progressed. This conversion was concomitant with a decrease in the frequency of regulatory T-cells and soft tissue IL10 and TGFβ expression. This immunophenotype was exacerbated in time of onset and magnitude in B6OEC.MyD88mice and was associated with an increase in alveolar bone loss. Together these data demonstrate that T-cell plasticity plays a role in PD whereby OEC-MyD88-signaling at least in part controls this plasticity. These data suggest that OECs can be a target for local modulation of T-cell plasticity as an intervention for the treatment of periodontal disease.

Peripherally induced regulatory T cells contribute to the control of autoimmune diabetes in the NOD mouse model

Type 1 diabetes (T1D) results from the autoimmune destruction of pancreatic beta cells and is partly caused by deficiencies in the Foxp3+ regulatory T-cell (Treg) compartment. Conversely, therapies that increase Treg function can prevent autoimmune diabetes in animal models. The majority of Tregs develop in the thymus (tTregs), but a proportion of Foxp3+ Tregs is generated in the periphery (pTregs) from Foxp3- CD4+ T-cell precursors. Whether pTregs play a distinct role in T1D has not yet been explored. We report here that pTregs are a key modifier of disease in the nonobese diabetic (NOD) mouse model for T1D. We generated NOD mice deficient for the Foxp3 enhancer CNS1 involved in pTreg induction. We show that CNS1 knockout decreased the frequency of pTregs and increased the risk of diabetes. Our results show that pTregs fulfill an important non-redundant function in the prevention of beta cell autoimmunity that causes T1D.

High circulating CD4+CD25hiFOXP3+ T-cell sub-population early after lung transplantation is associated with development of bronchiolitis obliterans syndrome

Chronic bronchiolitis obliterans syndrome (BOS) remains a major limitation for long-term survival after lung transplantation. The immune mechanisms involved and predictive biomarkers have yet to be identified. The purpose of this study was to determine whether peripheral blood T-lymphocyte profile could predict BOS in lung transplant recipients. An in-depth profiling of CD4+ and CD8+ T cells was prospectively performed on blood cells from stable (STA) and BOS patients with a longitudinal follow-up. Samples were analyzed at 1 and 6 months after transplantation, at the time of BOS diagnosis, and at an intermediate time-point at 6 to 12 months before BOS diagnosis. Although no significant difference was found for T-cell compartments at BOS diagnosis or several months beforehand, we identified an increase in the CD4+CD25hiFoxP3+ T-cell sub-population in BOS patients at 1 and 6 months after transplantation (3.39 ± 0.40% vs 1.67 ± 0.22% in STA, p < 0.001). A CD4+CD25hiFoxP3+ T-cell threshold of 2.4% discriminated BOS and stable patients at 1 month post-transplantation. This was validated on a second set of patients at 6 months post-transplantation. Patients with a proportion of CD4+CD25hiFoxP3+ T cells up to 2.4% in the 6 months after transplantation had a 2-fold higher risk of developing BOS. This study is the first to report an increased proportion of circulating CD4+CD25hiFoxP3+ T cells early post-transplantation in lung recipients who proceed to develop BOS within 3 years, which supports its use as a BOS predictive biomarker.

Enhanced expression of PD-1 and other activation markers by CD4+ T cells of young but not old patients with metastatic melanoma

The biological behavior of melanoma is unfavorable in the elderly when compared to young subjects. We hypothesized that differences in T-cell responses might underlie the distinct behavior of melanoma in young and old melanoma patients. Therefore, we investigated the circulating T-cell compartment of 34 patients with metastatic melanoma and 42 controls, which were classified as either young or old. Absolute numbers of CD4+ T cells were decreased in young and old melanoma patients when compared to the age-matched control groups. Percentages of naive and memory CD4+ T cells were not different when comparing old melanoma patients to age-matched controls. Percentages of memory CD4+ T cells tended to be increased in young melanoma patients compared to young controls. Proportions of naive CD4+ T cells were lower in young patients than in age-matched controls, and actually comparable to those in old patients and controls. This was accompanied with increased percentages of memory CD4+ T cells expressing HLA-DR, Ki-67, and PD-1 in young melanoma patients in comparison to the age-matched controls, but not in old patients. Proportions of CD45RA−FOXP3high memory regulatory T cells were increased in young and old melanoma patients when compared to their age-matched controls, whereas those of CD45RA+FOXP3low naive regulatory T cells were similar. We observed no clear modulation of the circulating CD8+ T-cell repertoire in melanoma patients. In conclusion, we show that CD4+ T cells of young melanoma patients show signs of activation, whereas these signs are less clear in CD4+ T cells of old patients.

Next-Generation Sequencing Analysis of the Human TCRγδ+ T-Cell Repertoire Reveals Shifts in Vγ- and Vδ-Usage in Memory Populations upon Aging.

Immunological aging remodels the immune system at several levels. This has been documented in particular for the T-cell receptor (TCR)αβ+ T-cell compartment, showing reduced naive T-cell outputs and an accumulation of terminally differentiated clonally expanding effector T-cells, leading to increased proneness to autoimmunity and cancer development at older age. Even though TCRαβ+ and TCRγδ+ T-cells follow similar paths of development involving V(D)J-recombination of TCR genes in the thymus, TCRγδ+ T-cells tend to be more subjected to peripheral rather than central selection. However, the impact of aging in shaping of the peripheral TRG/TRD repertoire remains largely elusive. Next-generation sequencing analysis methods were optimized based on a spike-in method using plasmid vector DNA-samples for accurate TRG/TRD receptor diversity quantification, resulting in optimally defined primer concentrations, annealing temperatures and cycle numbers. Next, TRG/TRD repertoire diversity was evaluated during TCRγδ+ T-cell ontogeny, showing a broad, diverse repertoire in thymic and cord blood samples with Gaussian CDR3-length distributions, in contrast to the more skewed repertoire in mature circulating TCRγδ+ T-cells in adult peripheral blood. During aging the naive repertoire maintained its diversity with Gaussian CDR3-length distributions, while in the central and effector memory populations a clear shift from young (Vγ9/Vδ2 dominance) to elderly (Vγ2/Vδ1 dominance) was observed. Together with less clear Gaussian CDR3-length distributions, this would be highly suggestive of differentially heavily selected repertoires. Despite the apparent age-related shift from Vγ9/Vδ2 to Vγ2/Vδ1, no clear aging effect was observed on the Vδ2 invariant T nucleotide and canonical Vγ9–Jγ1.2 selection determinants. A more detailed look into the healthy TRG/TRD repertoire revealed known cytomegalovirus-specific TRG/TRD clonotypes in a few donors, albeit without a significant aging-effect, while Mycobacterium tuberculosis-specific clonotypes were absent. Notably, in effector subsets of elderly individuals, we could identify reported TRG and TRD receptor chains from TCRγδ+ T-cell large granular lymphocyte leukemia proliferations, which typically present in the elderly population. Collectively, our results point to relatively subtle age-related changes in the human TRG/TRD repertoire, with a clear shift in Vγ/Vδ usage in memory cells upon aging.

Generation of alloreactivity-reduced donor lymphocyte products retaining memory function by fully automatic depletion of CD45RA-positive cells

Background aimsFor patients needing allogeneic stem cell transplantation but lacking a major histocompatibility complex (MHC)-matched donor, haplo-identical (family) donors may be an alternative. Stringent T-cell depletion required in these cases to avoid lethal graft-versus-host disease (GVHD) can delay immune reconstitution, thus impairing defense against virus reactivation and attenuating graft-versus-leukemia (GVL) activity. Several groups reported that GVHD is caused by cells residing within the naive (CD45RA+) T-cell compartment and proposed use of CD45RA-depleted donor lymphocyte infusion (DLI) to accelerate immune reconstitution. We developed and tested the performance of a CD45RA depletion module for the automatic cell-processing device CliniMACS Prodigy and investigated quality attributes of the generated products. MethodsUnstimulated apheresis products from random volunteer donors were depleted of CD45RA+ cells on CliniMACS Prodigy, using Good Manufacturing Practice (GMP)-compliant reagents and methods throughout. Using phenotypic and functional in vitro assays, we assessed the cellular constitution of CD45RA-depleted products, including T-cell subset analyses, immunological memory function and allo-reactivity. ResultsSelections were technically uneventful and proceeded automatically with minimal hands-on time beyond tubing set installation. Products were near-qualitatively CD45RA+ depleted, that is, largely devoid of CD45RA+ T cells but also of almost all B and natural killer cells. Naive and effector as well as γ/δ T cells were greatly reduced. The CD4:CD8 ratio was fivefold increased. Mixed lymphocyte reaction assays of the product against third-party leukocytes revealed reduced allo-reactivity compared to starting material. Anti-pathogen responses were retained. DiscussionThe novel, closed, fully GMP-compatible process on Prodigy generates highly CD45RA-depleted cellular products predicted to be clinically meaningfully depleted of GvH reactivity.

Calcineurin B in CD4+ T Cells Prevents Autoimmune Colitis by Negatively Regulating the JAK/STAT Pathway

Calcineurin (Cn) is a protein phosphatase that regulates the activation of the nuclear factor of activated T-cells (NFAT) family of transcription factors, which are key regulators of T-cell development and function. Here, we generated a conditional Cnb1 mouse model in which Cnb1 was specifically deleted in CD4+ T cells (Cnb1CD4 mice) to delineate the role of the Cn–NFAT pathway in immune homeostasis of the intestine. The Cnb1CD4 mice developed severe, spontaneous colitis characterized at the molecular level by an increased T helper-1-cell response but an unaltered regulatory T-cell compartment. Antibiotic treatment ameliorated the intestinal inflammation observed in Cnb1CD4 mice, suggesting that the microbiota contributes to the onset of colitis. CD4+ T cells isolated from Cnb1CD4 mice produced high levels of IFNγ due to increased activation of the JAK2/STAT4 pathway induced by IL-12. Our data highlight that Cn signaling in CD4+ T cells is critical for intestinal immune homeostasis in part by inhibiting IL-12 responsiveness of CD4+ T cells.

Impaired X-CGD T cell compartment is gp91phox-NADPH oxidase independent

Chronic granulomatous disease (CGD) is a phagocytic disorder characterized by a defective production of reactive oxygen species (ROSs). Although infections and granuloma formation are the most common manifestations in CGD patients, a significant number of patients experienced autoimmunity and inflammatory diseases suggesting that adaptive immune abnormalities might be involved.Here we investigated T-cell compartment and showed that CGD patients had a skewed TCRV-beta distribution in CD8+ T cells, particularly in older patients, and a reduced proliferative responses toward mitogens compared to healthy donors (HD). Afterwards we studied the role of gp91phox protein in causing these alterations and demonstrated that human T cells do not express gp91phox and TCR-stimulated ROS generation is gp91phox-NADPH oxidase independent. Finally, we proved that the NADPH oxidase is not active in the T cell compartment even when forcing gp91phox expression transducing T cells from X-CGD and HD with a SIN lentiviral vector (LVV) encoding the gp91phox cDNA.

Characterization of lymphopenia in patients with MS treated with dimethyl fumarate and fingolimod.

Objective:Lymphopenia is a common occurrence of disease-modifying therapies (DMTs) for relapsing-remitting MS (RRMS). The aim of this study was to dissect the prevalence of various lymphocyte subsets in patients with RRMS treated with 2 DMTs commonly associated with lymphopenia, dimethyl fumarate (DMF), and fingolimod (FTY).Methods:Multicolor flow cytometry and multiplex assays were used to identify up to 50 lymphocyte subpopulations and to examine the expression of multiple cytokines in selected patients. We compared patients untreated (NT) or treated with FTY or DMF who did (DMF-L) or did not (DMF-N) develop lymphopenia.Results:All FTY patients developed lymphopenia in both T-cell and B-cell compartments. CD41 T cells were more affected by this treatment than CD81 cells. In the B-cell compartment, the CD271IgD2 subpopulation was reduced. T cells but not B cells were significantly reduced in DMF-L. However, within the B cells, CD271 cells were significantly lower. Both CD41 and CD81 subpopulations were reduced in DMF-L. Within the remaining CD41 and CD81 compartments, there was an expansion of the naive subpopulation and a reduction of the effector memory subpopulation. Unactivated lymphocyte from DMF-L patients had significantly higher levels of interferon-γ, interleukin (IL)-12, IL-2, IL-4, IL-6, and IL-1β compared with DMF-N. In plasma, TNFβ was significantly higher in DMF-N and DMF-L compared with NT, whereas CCL17 was significantly higher in DMF-L compared with NT and DMF-N.Conclusions:This study shows that different treatments can target different lymphocyte compartments and suggests that lymphopenia can induce compensatory mechanisms to maintain immune homeostasis.

Multiparameter Intracellular Cytokine Staining.

Intracellular cytokine staining is a popular method for visualizing cellular responses, most often T-cell responses to antigenic or mitogenic stimulation. It can be coupled with staining for other functional markers, such as upregulation of CD107 or CD154, as well as phenotypic markers that define specific cellular subsets, e.g., effector and memory T-cell compartments, NK cells, or monocytes. Recent advances in multicolor flow cytometry instrumentation and software have allowed the routine combination of 12 or more markers, creating some technical and analytical challenges along the way, and exposing a need for standardization in the field. Here, we will review best practices for antibody panel design and procedural variables for multicolor intracellular cytokine staining, and present an optimized protocol with variations designed for use with specific markers and sample types.

CD30 Is Dispensable for T-Cell Responses to Influenza Virus and Lymphocytic Choriomeningitis Virus Clone 13 but Contributes to Age-Associated T-Cell Expansion in Mice.

CD30 is a tumor necrosis factor receptor (TNFR) family member whose expression is associated with Hodgkin’s disease, anaplastic large cell lymphomas, and other T and B lymphoproliferative disorders in humans. A limited number of studies have assessed the physiological role of CD30/CD30 ligand interactions in control of infection in mice. Here, we assess the role of CD30 in T-cell immunity to acute influenza and chronic lymphocytic choriomeningitis virus (LCMV) clone 13 infection, two viral infections in which other members of the TNFR superfamily are important for T-cell responses. We show that CD30 is expressed on activated but not resting CD4 and CD8 T cells in vitro, as well as on regulatory T cells and marginally on T helper 1 cells in vivo during influenza infection. Despite this, CD4 and CD8 T-cell expansion in response to influenza virus was comparable in CD30+/+ and CD30−/− littermates, with no discernable role for the pathway in the outcome of influenza infection. Similarly, during persistent infection with LCMV clone 13, CD30 plays no obvious role in CD4 or CD8 T-cell responses, the level of T-cell exhaustion or viral control. In contrast, in the steady state, we observed increased numbers of total CD4 and CD8 T cells as well as increased numbers of regulatory T cells in unimmunized older (~8 months) CD30+/+ but not in CD30−/− age-matched littermates. Naive T-cell numbers were unchanged in the aged CD30+/+ mice compared to their CD30−/− littermate controls, rather the T-cell expansions were explained by an increase in CD4+ and CD8+ CD44mid-hiCD62L− effector memory cells, with a similar trend in the central memory T-cell compartment. In contrast, CD30 did not impact the numbers of T cells in young mice. These data suggest a role for CD30 in the homeostatic regulation of T cells during aging, contributing to memory T-cell expansions, which may have relevance for CD30 expression in human T-cell lymphoproliferative diseases.

Preserved immune functionality and high CMV-specific T-cell responses in HIV-infected individuals with poor CD4+ T-cell immune recovery

Poor CD4+ T-cell recovery after cART has been associated with skewed T-cell maturation, inflammation and immunosenescence; however, T-cell functionality in those individuals has not been fully characterized. In the present study, we assessed T-cell function by assessing cytokine production after polyclonal, CMV and HIV stimulations of T-cells from ART-suppressed HIV-infected individuals with CD4+ T-cell counts >350 cells/μL (immunoconcordants) or <350 cells/μL (immunodiscordants). A group of HIV-uninfected individuals were also included as controls. Since CMV co-infection significantly affected T-cell maturation and polyfunctionality, only CMV+ individuals were analyzed. Despite their reduced and skewed CD4+ T-cell compartment, immunodiscordant individuals showed preserved polyclonal and HIV-specific responses. However, CMV response in immunodiscordant participants was significantly different from immunoconcordant or HIV-seronegative individuals. In immunodiscordant subjects, the magnitude of IFN-γ+ CD8+ and IL-2+ CD4+ T-cells in response to CMV was higher and differently associated with the CD4+ T-cell maturation profile., showing an increased frequency of naïve, central memory and EMRA CMV-specific CD4+ T-cells. In conclusion, CD4+ and CD8+ T-cell polyfunctionality was not reduced in immunodiscordant individuals, although heightened CMV-specific immune responses, likely related to subclinical CMV reactivations, may be contributing to the skewed T-cell maturation and the higher risk of clinical progression observed in those individuals.

A20 deletion in Tcells modulates acute graft-versus-host disease in mice.

The NF-κB regulator A20 limits inflammation by providing negative feedback in myeloid cells and B cells. Functional lack of A20 has been linked to several inflammatory and autoimmune diseases. To define how A20 affects the functionality of T effector cells in a highly inflammatory environment, we performed conventional allogeneic hematopoietic stem cell transplantation (allo-HSCT) with A20-deficient CD4+ and CD8+ donor Tcells in mice. Severity and mortality of graft-versus-host disease (GVHD) after allo-HSCT was drastically reduced in recipients transplanted with conventional doses of A20-deficient Tcells. Consistently, we found that the A20-deficient donor T-cell compartment was strongly diminished at various timepoints after allo-HSCT. However, proportionally more A20-deficient donor Tcells produced IFN-γ and systemic inflammation was elevated early after allo-HSCT. Consequently, increasing the dose of transplanted A20-deficient Tcells reversed the original phenotype and resulted in enhanced GVHD mortality compared to recipients that received A20+/+ Tcells. Still, A20-deficient Tcells, activated either through T cell receptor-dependent or -independent mechanisms, were less viable than control A20+/+ Tcells, highlighting that A20 balances both, T-cell activation and survival. Thus, our findings suggest that targeting A20 in Tcells may allow to modulate T-cell-mediated inflammatory diseases like GVHD.

Low antigen dose formulated in CAF09 adjuvant Favours a cytotoxic T-cell response following intraperitoneal immunization in Göttingen minipigs.

The relationship between the antigen dose and the quality of an immune response generated upon immunization is poorly understood. However, findings show that the immune system is indeed influenced by the antigen dose; hence underlining the importance of correctly determining which dose to use in order to generate a certain type of immune response. To investigate this area further, we used Göttingen minipigs asan animal model especially due to the similar body size and high degree of immunome similarity between humans and pigs. In this study, we show that both a humoral and a cell-mediated immune (CMI) response can be generated following intraperitoneal immunization with tetanus toxoid (TT) formulated in the CAF09 liposomal adjuvant. Importantly, a low antigen dose induced more TT-specific polyfunctional T cells, whereas antigen-specific IgG production was observed upon high-dose immunization. Independent of antigen dose, intraperitoneal administration of antigen increased the amount of TT-specific cytotoxic CD8β+ T cells within the cytokine-producing T-cell pool when compared to the non-cytokine producing T-cell compartment. Taken together, these results demonstrate that a full protein formulated in the CAF09 adjuvant and administered to pigs via the intraperitoneal route effectively generates a cytotoxic T-cell response. Moreover, we confirm the inverse relationship between the antigen dose and the induction of polyfunctional T cells in a large animal model. These finding can have implications for the design of upcoming vaccine trials aiming at establishing a cytotoxic T-cell response.

Reduced mitochondrial respiration in placentas from early-onset pre-eclampsia: Potential roles of the mitochondrial unfolded protein response

The landscape and function of the immune infiltrate of intrahepatic cholangiocarcinoma (iCCA), a rare, yet aggressive tumor of the biliary tract, remains poorly characterized, limiting development of successful immunotherapies. Herein, we aimed to define the molecular characteristics of tumor-infiltrating leukocytes with a special focus on CD4+ regulatory T cells (Tregs).We used high-dimensional single-cell technologies to characterize the T-cell and myeloid compartments of iCCA tissues, comparing these with their tumor-free peritumoral and circulating counterparts. We further used genomics and cellular assays to define the iCCA-specific role of a novel transcription factor, mesenchyme homeobox 1 (MEOX1), in Treg biology.We found poor infiltration of putative tumor-specific CD39+ CD8+ T cells accompanied by abundant infiltration of hyperactivated CD4+ Tregs. Single-cell RNA-sequencing identified an altered network of transcription factors in iCCA-infiltrating compared to peritumoral T cells, suggesting reduced effector functions by tumor-infiltrating CD8+ T cells and enhanced immunosuppression by CD4+ Tregs. Specifically, we found that expression of MEOX1 was highly enriched in tumor-infiltrating Tregs, and demonstrated that MEOX1 overexpression is sufficient to reprogram circulating Tregs to acquire the transcriptional and epigenetic landscape of tumor-infiltrating Tregs. Accordingly, enrichment of the MEOX1-dependent gene program in Tregs was strongly associated with poor prognosis in a large cohort of patients with iCCA.We observed abundant infiltration of hyperactivated CD4+ Tregs in iCCA tumors along with reduced CD8+ T-cell effector functions. Interfering with hyperactivated Tregs should be explored as an approach to enhance antitumor immunity in iCCA.Immune cells have the potential to slow or halt the progression of tumors. However, some tumors, such as intrahepatic cholangiocarcinoma, are associated with very limited immune responses (and infiltration of cancer-targeting immune cells). Herein, we show that a specific population of regulatory T cells (a type of immune cell that actually suppresses the immune response) are hyperactivated in intrahepatic cholangiocarcinoma. Targeting these cells could enable cancer-targeting immune cells to act more effectively and should be looked at as a potential therapeutic approach to this aggressive cancer type.

Host-microbiota interactions and adaptive immunity.

All mucosal surfaces are colonized with a vast number of microbes, which are essential for stimulating and regulating the immune system. While intrinsic and innate mechanisms exist to promote a strong barrier between the microbiota and the host to ensure compartmentalization, the microbiota is also able to induce robust adaptive immunity. In this review, we discuss the interplay between the microbiota and the adaptive immune system, with a focus on the induction of mucosal and systemic antibody responses and newly defined roles of maternal antibodies. We also highlight recent studies that aim to decipher microbial antigen-specificity of the T-cell compartment.

Dynamics of Recent Thymic Emigrants in Young Adult Mice.

The peripheral naive T-cell pool is generally thought to consist of a subpopulation of recent thymic emigrants (RTEs) and a subpopulation of mature naive (MN) T cells with different dynamics. Thymus transplantation and adoptive transfer studies in mice have provided contradicting results, with some studies suggesting that RTEs are relatively short-lived cells, while another study suggested that RTEs have a survival advantage. We here estimate the death rates of RTE and MN T cells by performing both thymus transplantations and deuterium labeling experiments in mice of at least 12 weeks old, an age at which the size of the T-cell pool has stabilized. For CD4+ T cells, we found the total loss rate from the RTE compartment (by death and maturation) to be fourfold faster than that of MN T cells. We estimate the death rate of CD4+ RTE to be 0.046 per day, which is threefold faster than the total loss rate from the MN T-cell compartment. For CD8+ T cells, we found no evidence for kinetic differences between RTE and MN T cells. Thus, our data support the notion that in young adult mice, CD4+ RTE are relatively short-lived cells within the naive CD4+ T-cell pool.

Epstein-Barr Virus Type 2 Infects T Cells in Healthy Kenyan Children.

The 2 strains of Epstein-Barr virus (EBV), EBV type 1 (EBV-1) and EBV-2, differ in latency genes, suggesting that they use distinct mechanisms to establish latency. We previously reported that EBV-2 infects T cells in vitro. In this study, we tested the possibility that EBV-2 infects T cells in vivo. Purified T-cell fractions isolated from children positive for EBV-1 or EBV-2 and their mothers were examined for the presence of EBV and for EBV type. We detected EBV-2 in all T-cell samples obtained from EBV-2-infected children at 12 months of age, with some children retaining EBV-2-positive T cells through 24 months of age, suggesting that EBV-2 persists in T cells. We were unable to detect EBV-2 in T-cell samples from mothers but could detect EBV-2 in samples of their breast milk and saliva. These data suggest that EBV-2 uses T cells as an additional latency reservoir but that, over time, the frequency of infected T cells may drop below detectable levels. Alternatively, EBV-2 may establish a prolonged transient infection in the T-cell compartment. Collectively, these novel findings demonstrate that EBV-2 infects T cells in vivo and suggest EBV-2 may use the T-cell compartment to establish latency.