Teff Subsets Research Articles

Integrated analysis of single-cell data on role of NKG7high CD8+ Teff cells in driving immune-related adverse events.

e24114 Background: Immune-related adverse events (irAEs) frequently occur during immunotherapy and can impact various organ systems, which dampen the clinical outcomes of immune checkpoint inhibitors (ICIs). However, the precise immune hallmarks associated with irAEs remain further explored. Methods: We collected public (Bukhari et al., Zhu et al., Su et al., and Ma et al.) and our own scRNA-seq data across patients with different irAE types or without irAEs. By comparing T cell compositions between irAE and no-irAE patients, the subcluster correlated with the occurrence of irAE was identified. Subsequently, the integrated analyses were performed to explore its mechanisms in driving irAEs in both peripheral blood and local tissues. Results: Compared to no-irAE patients, a subcluster of effector T (Teff) cells was observed to increase notably in the peripheral blood of irAE patients during immunotherapy. This specific subcluster, named "NKG7high CD8+ Teff cells," was characterized by the significant expression of effector genes such as GZMH, CCL5, and especially NKG7. In contrast to other CD8+ T cells, the NKG7high CD8+ Teff cells exhibited stronger cytotoxicity functions, increased exosome secretion, and enhanced MIF-CD74 interaction with monocytes, which suggests the mechanistic link between its increased infiltration and the development of irAEs. Further investigation showed these characteristics were more remarkable in NKG7high CD8+ Teff from irAE patients than no-irAE patients. Subsequently, the increase of NKG7high CD8+ Teff during immunotherapy was validated in our own scRNA from immune thyroiditis patients, which was not observed in no-irAE patients. Across various irAE types, NKG7high CD8+ Teff subsets, along with their NKG7 expression, demonstrated heightened infiltration and expression in immune-related arthritis and myocarditis samples. After investigating the role of NKG7high CD8+ Teff in peripheral blood, we focused on its distribution and roles in local irAE tissue. NKG7high CD8+ Teff cells accumulated in immune-related thyroiditis tissues, and recruited macrophages through the IFNG and CSF1 signaling pathways, thereby inducing an immune overreaction. Meanwhile, in immune-related myocarditis mice heart tissues, NKG7high CD8+ Teff cells could interact with macrophages via the SPP1 signaling pathway and cause endothelial cell damage through the FASL-FAS pathway. Conclusions: This comprehensive study revealed the intricate mechanisms of NKG7high CD8+ Teff in inducing irAEs, providing valuable insights into their roles and potential implications in irAE treatment.

Neonatal Immunity to Malaria using a mouse model

Abstract High mortality rates caused by malaria are seen in children under five years, but there is limited knowledge on neonatal immunity to the Plasmodium infection due to the lack of a reliable neonatal animal model to study the disease in children. By utilizing a newly developed young rodent model in our lab, we have observed that purified CD4+ T cells from day 14 old young mice (pups) proliferate slower than those purified from 8-week adult mice when stimulated in vitro. To investigate neonatal CD4+ T cell response to malaria, we infected 14-day old pups or adult mice with Plasmodium chabaudi and determined the activation status (CD127−CD44+CD11a+) and differentiation of effector (Teff) subsets, using the expression of CD62L or CD27. Pup CD4+ T cells were activated by downregulating CD127, even though in lower proportions and numbers when compared to adult CD4+ T cells. Surprisingly, there were more proportions of TeffEarly (CD27+CD62L+) and TeffInt (CD27+CD62L−) subsets in the pups than adult mice, which had mostly TeffLate (CD27−CD62L−), suggesting that the transition of Teff subsets is slower in the young mice. We next determined cytokine secretion and Tbet expression by the Teff. Apart from IL-2 which was high in the pups, there was no difference in the proportions of protective cytokines including IFNγ, IL-10 and TNFα in both groups. Effector CD4+ T cells from the pups expressed high proportions of the Tbet transcription factor when compared to adult cells. Taken together, these data suggest that pup CD4 T cells may require more Tbet to differentiate into functional effector cells during Plasmodium infection. Supported by Depart of Biology Appalachian State University

Metabolic reprogramming by ex vivo glutamine inhibition endows CAR-T cells with less-differentiated phenotype and persistent antitumor activity

The inadequate in vivo persistence of chimeric antigen receptor (CAR)-modified T cells has been shown to lead to poor therapeutic efficacy and disease recurrence. In vivo persistence is associated with the differentiation subsets infused, with less differentiated TN or TCM conferring superior renewal capacity and antitumor immunity compared to TEM or TEFF. However, ex vivo expanded CAR-T cells exhibit phenotypic heterogeneity with majority of TEM or TEFF subsets and very low populations of TN and TCM. The transition of differentiation subsets is closely correlated with T cell metabolism fitness. Effector T cell differentiation from TN or TCM requires glutamine uptake and metabolism. Using a CD19-specific CAR, we demonstrated that glutamine inhibition by adding the glutamine antagonist 6-Diazo-5-oxo-l-norleucine (DON) into the culture endows CAR-T cells with enhanced mitochondrial OXPHOS utilizing fatty acids and reduced glycolytic activity, and retains more TN or TCM subsets. DON- pretreated CAR-T cells exhibited stronger cytotoxic lysis in vitro and more robust elimination of tumor burdens in vivo. This study suggests that glutamine inhibition ex vivo would be a potential approach for modulating metabolism and differentiation state to improve the efficacy of CAR-T cell therapy.

Abstract P077: Composition of CD4 T cell subsets and impact on tumor growth control across mouse syngeneic tumor models

Abstract CD4 T cells include multiple sublineages orchestrating a broad range of effector activities during the initiation, promotion, and progression of carcinogenesis. Although regulatory T cells (Tregs) are well-characterized to promote tumor progression, the impact of effector CD4+ T cell subsets (Teff) in anti-tumor immunity is less well known. Further, the relative contribution of Teff and Treg cell subsets in different syngeneic tumor models has not been characterized. We observed that CD4 depletion had significantly different impact of tumor growth across different syngeneic tumor models: no effect on MC38 tumor growth; enhanced tumor growth in CT26.KSA tumor model; while almost complete tumor regression in the EMT-6 tumor model. We hypothesized that each tumor model has a vastly different composition in the CD4 T cell compartment. To test this, we characterized expression of activation and CD4 T cell differentiation markers as well as cytokine production from CD4 TILs in each of the syngeneic tumor models. We found that while effector CD4 TILs (FoxP3−CD4+) from MC38 and CT26.KSA tumors expressed high levels activation and differentiation markers, Teff from EMT-6 tumors expressed very low levels of T cell activation and differentiation markers, suggesting the Teff in EMT-6 tumors are largely dysfunctional. Ex vivo restimulation of tumor samples with anti-CD3/anti-CD28 promoted IFNγ production in CD4 TILs from MC38 and CT26.KSA tumor models, but not from EMT-6 tumor models, further supporting that Teff from MC38 and CT26.KSA tumors remain highly active, while CD4 TILs from EMT-6 tumors are dysfunctional. When looking at the Treg compartment, the frequency of Tregs in CT26.KSA tumors was reduced compared to MC38 and EMT-6 tumors. Further, Tregs in MC38 and EMT-6 tumors expressed very high levels of CD69, a marker of highly immunosuppressive Tregs, while Tregs in CT26.KSA tumors expressed lower levels of CD69, suggesting that these Tregs may be less immunosuppressive. In summary, the CD4 T cell compartment is vastly different across CT26.KSA, MC38 and EMT-6 syngeneic tumor models, resulting in very different impact of tumor growth control. Citation Format: Chunxiao Xu, Lindsay Webb, Sireesha Yalavarthi, Clotilde Bourin, Jacques Moisan. Composition of CD4 T cell subsets and impact on tumor growth control across mouse syngeneic tumor models [abstract]. In: Abstracts: AACR Virtual Special Conference: Tumor Immunology and Immunotherapy; 2021 Oct 5-6. Philadelphia (PA): AACR; Cancer Immunol Res 2022;10(1 Suppl):Abstract nr P077.

Methotrexate Restores CD73 Expression on Th1.17 in Rheumatoid Arthritis and Psoriatic Arthritis Patients and May Contribute to Its Anti-Inflammatory Effect through Ado Production

Objectives: Th1.17 are highly polyfunctional, potentially harmful CD4+ effector T cells (Teff) through IFN-γ and IL-17A coproduction. Th1.17 take part in the pathophysiology of rheumatoid arthritis (RA) and psoriatic arthritis (PsA), in which their hyper activation results in part from defects in negative regulation mechanisms. We recently demonstrated that the ecto-nucleotidase CD73 delineates a Th1.17-enriched Teff population and acts as an endogenous regulatory mechanism. Because Methotrexate (MTX), used as first line treatment of RA and PsA, increases extracellular concentrations of AMP and immunosuppressive adenosine, we investigated the modulation of CD73 by MTX treatment on Teff in RA/PsA patients. Methods: In a prospective cohort of 26 RA and 15 PsA patients before or under MTX treatment, we evaluated CD73 expression on blood Teff subsets, their cytokine production and AMPase functions. Results: We showed a decreased CD73 expression on Th1.17 and Th1 in untreated patients compared to healthy donors that was partly restored under MTX. This decrease in untreated patients leads to a halved Ado production by Th1.17 cells. CD73+ Teff remained functional under MTX treatment, but their CD73 re-expression may contribute to control their activation. Conclusion: Our study unveils uncovered mode of action of MTX on Teff subsets modulation and in the adenosine-dependent termination of inflammation in RA and PsA.

Identification and functional characterization of CD8+ T regulatory cells in type 1 diabetes patients.

Type 1 diabetes is an autoimmune disease where autoreactive T lymphocytes destroy pancreatic beta cells. We previously reported a defect in CD4+ Tregs cell proliferation and reduced CD4+ Tregs PD-1 expression in patients. Another ‘memory-like’ regulatory subset, CD8+ Tregs, evaluated as CD8+CD25+FOXP3+, has recently raised interest for their effective suppressive activity. Different CD8+ T cell populations, their proliferation capacity and expression of PD-1 molecule were evaluated by flow-cytometer analysis in newly diagnosed, long-term Type 1 diabetes patients compared to healthy normal donors. Under basal conditions, CD8+ Tregs and CD8+ Teffs were seemingly represented among study groups while there was evidence of diminished expression of PD-1 in Teff subsets of long-term patients. After 3 days of PMA/ionomycin stimulation, patients CD8+ Tregs showed decreased percentage in respect to control group. CD8+ Teffs were instead increased in long-term diabetics versus controls. PD-1+CD8+ Tregs were represented at a much lower percentage in long-term diabetic patients, in respect to controls. Importantly, patients CD8+ Tregs and CD8+ Teffs presented a significant proliferation defect in respect to the control group. In conclusion, our study indicates that a defect of CD8+ Tregs is observed in diabetics. This subset could thus represent a novel target of immunotherapy in patients.

Metabolomics analysis reveals differential T cell serine metabolism as a target in autoimmunity.

Abstract Inflammatory cytokines are key players in the pathogenesis of autoimmune disorders where their signaling leads to inappropriate balance between effector CD4 T-cells (Teff), Th1 and Th17, and the immunosuppressive regulatory T-cells (Treg). Each subset utilizes a distinctive metabolic program but how cytokines induce differential metabolic rewiring and what aspects of it are critical for the functioning and lineage stability of Teff subsets and Treg is not understood. To delineate pathogenicity-associated metabolic programs, we performed global untargeted metabolomics mass spectrometry (MS) in in vitro cytokine-differentiated mouse Th1, Th17 and Treg cells with varying degrees of pathogenicity over time. Integrating our data-driven metabolic network with global proteomics profiling and cytokine secretion allowed us to examine metabolic pathways at metabolite-enzyme level. Metabolites at the interface of amino acid metabolism, particularly glutamine and serine, glycolysis, the TCA cycle and nucleotide synthesis were the most differentially changed. Serine limitation or pharmacological inhibition indicated differential coupling of serine/one-carbon metabolism to T-cell proliferation, lineage choices and the production of cytokines IL-17 or IFNγ. Furthermore, targeting this pathway promoted Treg lineage development in the presence of pathogenic cytokines and prevented loss of Treg transcription factor FoxP3 upon re-stimulation. In vivo, spinal cord infiltrating T-cells in murine experimental autoimmune encephalomyelitis had altered serine metabolic pathway. Our findings identify key areas of T-cell metabolism that may offer a new category of therapeutic targets for autoimmune and inflammatory disease.

Protection by and maintenance of CD4 effector memory and effector T cell subsets in persistent malaria infection.

Protection at the peak of Plasmodium chabaudi blood-stage malaria infection is provided by CD4 T cells. We have shown that an increase in Th1 cells also correlates with protection during the persistent phase of malaria; however, it is unclear how these T cells are maintained. Persistent malaria infection promotes protection and generates both effector T cells (Teff), and effector memory T cells (Tem). We have previously defined new CD4 Teff (IL-7Rα-) subsets from Early (TeffEarly, CD62LhiCD27+) to Late (TeffLate, CD62LloCD27-) activation states. Here, we tested these effector and memory T cell subsets for their ability to survive and protect in vivo. We found that both polyclonal and P. chabaudi Merozoite Surface Protein-1 (MSP-1)-specific B5 TCR transgenic Tem survive better than Teff. Surprisingly, as Tem are associated with antigen persistence, Tem survive well even after clearance of infection. As previously shown during T cell contraction, TeffEarly, which can generate Tem, also survive better than other Teff subsets in uninfected recipients. Two other Tem survival mechanisms identified here are that low-level chronic infection promotes Tem both by driving their proliferation, and by programming production of Tem from Tcm. Protective CD4 T cell phenotypes have not been precisely determined in malaria, or other persistent infections. Therefore, we tested purified memory (Tmem) and Teff subsets in protection from peak pathology and parasitemia in immunocompromised recipient mice. Strikingly, among Tmem (IL-7Rαhi) subsets, only TemLate (CD62LloCD27-) reduced peak parasitemia (19%), though the dominant memory subset is TemEarly, which is not protective. In contrast, all Teff subsets reduced peak parasitemia by more than half, and mature Teff can generate Tem, though less. In summary, we have elucidated four mechanisms of Tem maintenance, and identified two long-lived T cell subsets (TemLate, TeffEarly) that may represent correlates of protection or a target for longer-lived vaccine-induced protection against malaria blood-stages.

Old Mice Accumulate Activated Effector CD4 T Cells Refractory to Regulatory T Cell-Induced Immunosuppression.

Chronic low-grade inflammation and reduced lymphocyte potency are implicated in the pathogenesis of major illnesses associated with aging. Whether this immune phenotype results from a loss of cell-mediated regulation or intrinsic dysregulated function of effector T cells (Teffs) requires further research. Here, we report that, as compared with young C57BL6 mice, old mice show an increased frequency of CD4+CD62L− Teffs with a dysregulated activated phenotype and markedly increased effector functions. Analysis of the frequency and suppressive function of CD4+FoxP3+ regulatory T cells (Tregs) indicates an increase in the frequency of FoxP3+ T cells with aging which, however, occurs within the CD4+CD25− T cells. Furthermore, whereas Tregs from young and old mice similarly suppress Teffs from young mice, both have a compromised suppressive capacity of Teffs from old mice, a phenomenon which is partially recovered in the presence of IL-2-producing CD4+CD62L+ non-Teffs. Finally, we observed that Teff subsets from old mice are enriched with IL-17A-producing T cells and exhibit intrinsically dysregulated expression of genes encoding cell-surface molecules and transcription factors, which play a key role in T-cell activation and regulation. We, thus, demonstrate an age-related impairment in the regulation of effector CD4 T cells, which may underlie the higher risk for destructive inflammation associated with aging.

The Chemokine Receptor CX3CR1 Defines Three Antigen-Experienced CD8 T Cell Subsets with Distinct Roles in Immune Surveillance and Homeostasis

Infections induce pathogen-specific Tcell differentiation into diverse effectors (Teff) that give rise to memory (Tmem) subsets. The cell-fate decisions and lineage relationships that underlie these transitions are poorly understood. Here, we found that the chemokine receptor CX3CR1 identifies three distinct CD8+ Teff and Tmem subsets. Classical central (Tcm) and effector memory (Tem) cells and their corresponding Teff precursors were CX3CR1- and CX3CR1high, respectively. Viral infection also induced a numerically stable CX3CR1int subset that represented ∼15% of blood-borne Tmem cells. CX3CR1int Tmem cells underwent more frequent homeostatic divisions than other Tmem subsets and not only self-renewed, but also contributed to the expanding CX3CR1- Tcm pool. Both Tcm and CX3CR1int cells homed to lymphnodes, but CX3CR1int cells, and not Tem cells, predominantly surveyed peripheral tissues. As CX3CR1int Tmem cells present unique phenotypic, homeostatic, and migratory properties, we designate this subset peripheral memory (tpm) cells and propose that tpm cells are chiefly responsible for the global surveillance of non-lymphoid tissues.

Identification of two T cell subsets that protect and survive long-term in malaria infection

Abstract Malaria and other chronic infections generate effector and effector memory T cells, but the infection is not completely controlled. While the parasite is present, some level of protection is provided, but this decays as specific cytokine production disappears. This indicates that protection in chronic malaria is partly provided by continuously activated CD4 T cells. Current vaccination protocols also result in immunity that decays. In order to invent new vaccination strategies to combat this problem, we need to understand what T cell types are potentially both protective and long-lived. Therefore, we tested effector (Teff), central (Tcm), and effector memory (Tem) T cell subsets for their ability to both protect and survive in vivo. Using transgenic T cells specific for the Merozoite Surface Protein-1 of Plasmodium chabaudi, and our previously defined effector and memory subsets, we sort-purified individual cell populations, and tested their ability to protect in combination with immune B cells. Strikingly, Teff reduce parasitemia by half, at all stages of effector maturation. When Teff subsets were rested in naïve animals to allow generation of memory, the least mature Teff subset, TeffEarly, which we have shown generate the most memory cells, decreased parasitemia the most on infection of adoptive hosts. Interestingly, these earliest activated T cells survive as well as the memory subsets, of which only Tem Late (CD62LloCD27−) reduced parasite by 10%. Therefore, we have identified two long-lived T cell subsets that may represent a correlate of protection or a target for longer-lived vaccine-induced protection against malaria.

CX3CR1 distinguishes three antigen-experienced CD8 T cell subsets with distinct migratory, functional and homeostatic properties

Abstract Following infection, pathogen-specific T cells differentiate into diverse short-lived effectors (TEff) that give rise to long-lived memory (TMem) subsets. These T cell fate decisions and lineage relationships are poorly understood, in part, because available subset-defining markers do not adequately reflect existing heterogeneities. Here, we report that CX3CR1 identifies three distinct CD8+ TEff and TMem subsets. CX3CR1 expression levels on TEff were indicative of TEff differentiation, and predictive of the magnitude and type of memory progeny. Classical central memory (TCM) and effector memory cells (TEM) were CX3CR1– and CX3CR1high, respectively. In addition, we identified a hitherto unrecognized CX3CR1int population. The fraction of CX3CR1int cells among antigen-experienced TMem was remarkably stable over the course of a year, while TEM gradually declined and TCM increased to be the largest subset by 10 months. Interestingly, CX3CR1int TMem had the highest proliferation rate of the three TMem subsets. While TCM and TEM were phenotypically stable over >10 weeks at steady state, CX3CR1int TMem not only self-renewed, but also gave rise to bonafide TCM. This suggests that CX3CR1int TMem may contribute to the gradual increase in TCM. In contrast, re-infection resulted in unidirectional differentiation from TCM to CX3CR1int TMem to TEM. The newly identified CX3CR1int TMem displayed unique migratory properties. Unlike CX3CR1high TEM, CX3CR1int gradually acquired lymph node homing capability. Moreover, parabiosis experiments and analysis of recirculating memory cells in thoracic duct lymph revealed that CX3CR1int TMem, not TEM, are the predominant T cell subset surveying non-lymphoid peripheral tissues.

Adenovirus-specific T-cell Subsets in Human Peripheral Blood and After IFN-γ Immunomagnetic Selection.

Adoptive antiviral cellular immunotherapy by infusion of virus-specific T cells (VSTs) is becoming an alternative treatment for viral infection after hematopoietic stem cell transplantation. The T memory stem cell (TSCM) subset was recently described as exhibiting self-renewal and multipotency properties which are required for sustained efficacy in vivo. We wondered if such a crucial subset for immunotherapy was present in VSTs. We identified, by flow cytometry, TSCM in adenovirus (ADV)-specific interferon (IFN)-γ+ T cells before and after IFN-γ-based immunomagnetic selection, and analyzed the distribution of the main T-cell subsets in VSTs: naive T cells (TN), TSCM, T central memory cells (TCM), T effector memory cell (TEM), and effector T cells (TEFF). In this study all of the different T-cell subsets were observed in the blood sample from healthy donor ADV-VSTs, both before and after IFN-γ-based immunomagnetic selection. As the IFN-γ-based immunomagnetic selection system sorts mainly the most differentiated T-cell subsets, we observed that TEM was always the major T-cell subset of ADV-specific T cells after immunomagnetic isolation and especially after expansion in vitro. Comparing T-cell subpopulation profiles before and after in vitro expansion, we observed that in vitro cell culture with interleukin-2 resulted in a significant expansion of TN-like, TCM, TEM, and TEFF subsets in CD4IFN-γ T cells and of TCM and TEM subsets only in CD8IFN-γ T cells. We demonstrated the presence of all T-cell subsets in IFN-γ VSTs including the TSCM subpopulation, although this was weakly selected by the IFN-γ-based immunomagnetic selection system.

Inhibition of Autoimmune Diabetes in NOD Mice by miRNA Therapy.

Autoimmune destruction of the pancreatic islets in Type 1 diabetes is mediated by both increased proinflammatory (Teff) and decreased regulatory (Treg) T lymphocytes resulting in a significant decrease in the Treg:Teff ratio. The non-obese diabetic (NOD) mouse is an excellent in vivo model for testing potential therapeutics for attenuating the decrease in the Treg:Teff ratio and inhibiting disease pathogenesis. Here we show for the first time that a bioreactor manufactured therapeutic consisting of a complex of miRNA species (denoted as TA1) can effectively reset the NOD immune system from a proinflammatory to a tolerogenic state thus preventing or delaying autoimmune diabetes. Treatment of NOD mice with TA1 resulted in a systemic broad-spectrum upregulation of tolerogenic T cell subsets with a parallel downregulation of Teff subsets yielding a dramatic increase in the Treg:Teff ratio. Moreover, the murine-derived TA1 was highly effective in the inhibition of allorecognition of HLA-disparate human PBMC. TA1 demonstrated dose-responsiveness and exhibited equivalent or better inhibition of allorecognition driven proliferation than etanercept (a soluble TNF receptor). These findings demonstrate that miRNA-based therapeutics can effectively attenuate or arrest autoimmune disease processes and may be of significant utility in a broad range of autoimmune diseases including Type 1 diabetes.

Prenatal Allospecific Tolerance Is Characterized By Early Treg Expansion and a Surprisingly Slow Pace for Teff Clonal Deletion

Prenatal transplantation capitalizes on the unique fetal environment, allowing for life-long engraftment of allogeneic stem cells without the need for harsh conditioning regimens. A prerequisite for stable engraftment of allogeneic cells likely requires the negative selection of donor-specific host effector T cells (Teff) and the support of donor-specific regulatory T cells (Tregs). However, little is known about the interplay between these cell types during development. The purpose of this study was to characterize the dynamic relationship between donor-specific Teff and Tregs as they emerge during development.Prenatal allogeneic chimeras were established by in utero transplantation of E14 fetal liver light density cells into age-matched allogeneic fetal recipients (Balb/c to B6 or B6 to Balb/c). In this model, immature T cells from B6 mice expressing TCRv-beta-5, 11, and 12 are negatively selected by mtv-8 superantigen complexed with I-E class MHC II on Balb/c cells. As alpha/beta TCR rearrangement does not occur until E16, this established transplantation model allows for alloantigen to be present from the earliest stages of thymic selection. Kinetic analysis of donor-specific T cell populations was performed in peripheral blood paired with in depth analysis in thymus and spleen in control and chimeric mice.Negative selection of donor-specific Teff cells occurs at an unexpectedly slow pace in Balb/c to B6 prenatal chimeras. Donor-specific CD4 and CD8 Teff are significantly decreased in frequency at 4 weeks of age but do not reach maximal deletion until 12 weeks of age (TCRv-beta-5 data shown in Figure A). Further analysis demonstrated that this slow elimination of donor-specific Teff was paired with an early increase in the frequency of donor-specific Tregs at 4 weeks of age (TCRv-beta-5 data shown in Figure B.) This increase in donor-specific Tregs likely occurred as a result of peripheral expansion as there was no change in the frequency of donor-specific Tregs in the thymus (Figure B) and no change in the frequency of these cells that expressed the markers of thymically derived natural Tregs neuropilin-1 or helios (data not shown). In agreement with this hypothesis, donor-specific splenic Tregs incorporated BrdU at a higher rate than other Tregs in young mice indicating a potential expansion of donor-specific Tregs in the periphery (TCRv-beta-5 data shown in Figure C.)Collectively, these data demonstrate that prenatal transplantation is characterized by: 1) a surprisingly slow reduction of donor-specific Teff subsets; 2) an early expansion of donor-specific Tregs. Further studies will explore the role of donor-specific Tregs in controlling early immunity to prenatally encountered antigens. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Early effector cells survive the contraction phase in malaria infection and generate both central and effector memory T cells.

CD4 T cells orchestrate immunity against blood-stage malaria. However, a major challenge in designing vaccines to the disease is poor understanding of the requirements for the generation of protective memory T cells (Tmem) from responding effector T cells (Teff) in chronic parasite infection. In this study, we use a transgenic mouse model with T cells specific for the merozoite surface protein (MSP)-1 of Plasmodium chabaudi to show that activated T cells generate three distinct Teff subsets with progressive activation phenotypes. The earliest observed Teff subsets (CD127(-)CD62L(hi)CD27(+)) are less divided than CD62L(lo) Teff and express memory genes. Intermediate (CD62L(lo)CD27(+)) effector subsets include the most multicytokine-producing T cells, whereas fully activated (CD62L(lo)CD27(-)) late effector cells have a terminal Teff phenotype (PD-1(+), Fas(hi), AnnexinV(+)). We show that although IL-2 promotes expansion, it actually slows terminal effector differentiation. Using adoptive transfer, we show that only early Teff survive the contraction phase and generate the terminal late Teff subsets, whereas in uninfected recipients, they become both central and effector Tmem. Furthermore, we show that progression toward full Teff activation is promoted by increased duration of infection, which in the long-term promotes Tem differentiation. Therefore, we have defined markers of progressive activation of CD4 Teff at the peak of malaria infection, including a subset that survives the contraction phase to make Tmem, and show that Ag and cytokine levels during CD4 T cell expansion influence the proportion of activated cells that can survive contraction and generate memory in malaria infection.

Decreasing initial stimulation increases generation of early effector cells that survive the contraction phase in malaria infection (MPF2P.754)

Abstract CD4 T cells orchestrate immunity against blood-stage malaria. However, a major challenge in designing malaria vaccines is understanding generation of memory from effector T cells (Teff) in chronic infection. We use a transgenic mouse model with T cells specific for the Merozoite Surface Protein (MSP)-1 of Plasmodium chabaudi to show that activated T cells generate three Teff (CD127-) subsets representing progressive activation. The earliest observed subset (CD62LhiCD27+) divides first, and maintains memory gene expression. An intermediate (CD62LloCD27+) effector subset has more multi-cytokine producing T cells and a terminal phenotype, including expression of PD-1 and Fas. Fully activated (CD62LloCD27-) late effector cells contain fewer cytokine+ and more AnnexinVhi apoptotic cells. Using an adoptive transfer system, we show the ability of CD62Lhi Teff to generate the terminal Teff subsets but also to survive the contraction phase better than the CD62Llo subsets. Furthermore, we show that progression towards terminal differentiation increases with duration of infection, but is inhibited by IL-2, which promotes expansion but not progression. Therefore, we have defined markers of progressive activation of CD4 Teff at the peak of malaria infection, and shown that CD127-CD62Lhi Teff survive the contraction phase. Therefore, antigen and cytokine levels during CD4 T cell expansion influence the proportion of activated cells that can survive T cell contraction in malaria infection.

Regulatory T cells in central nervous system injury: a double-edged sword.

Previous research investigating the roles of T effector (T(eff)) and T regulatory (T(reg)) cells after injury to the CNS has yielded contradictory conclusions, with both protective and destructive functions being ascribed to each of these T cell subpopulations. In this work, we study this dichotomy by examining how regulation of the immune system affects the response to CNS trauma. We show that, in response to CNS injury, T(eff) and T(reg) subsets in the CNS-draining deep cervical lymph nodes are activated, and surgical resection of these lymph nodes results in impaired neuronal survival. Depletion of T(reg), not surprisingly, induces a robust T(eff) response in the draining lymph nodes and is associated with impaired neuronal survival. Interestingly, however, injection of exogenous T(reg) cells, which limits the spontaneous beneficial immune response after CNS injury, also impairs neuronal survival. We found that no T(reg) accumulate at the site of CNS injury, and that changes in T(reg) numbers do not alter the amount of infiltration by other immune cells into the site of injury. The phenotype of macrophages at the site, however, is affected: both addition and removal of T(reg) negatively impact the numbers of macrophages with alternatively activated (tissue-building) phenotype. Our data demonstrate that neuronal survival after CNS injury is impaired when T(reg) cells are either removed or added. With this exacerbation of neurodegeneration seen with both addition and depletion of T(reg), we recommend exercising extreme caution when considering the therapeutic targeting of T(reg) cells after CNS injury, and possibly in chronic neurodegenerative conditions.

Aging disturbs the balance between effector and regulatory CD4+ T cells

Healthy aging requires an optimal balance between pro-inflammatory and anti-inflammatory immune responses. Although CD4+ T cells play an essential role in many immune responses, few studies have directly assessed the effect of aging on the balance between effector T (Teff) cells and regulatory T (Treg) cells. Here, we determined if and how aging affects the ratio between Treg and Teff cells. Percentages of both naive Treg (nTreg; CD45RA+CD25intFOXP3low) and memory Treg (memTreg; CD45RA-CD25highFOXP3high) cells were determined by flow cytometry in peripheral blood samples of healthy individuals of various ages (20–84years). Circulating Th1, Th2 and Th17 effector cells were identified by intracellular staining for IFN-γ, IL-4 and IL-17, respectively, upon in vitro stimulation with PMA and calcium ionophore. Whereas proportions of nTreg cells declined with age, memTreg cells increased. Both Th1 and Th2 cells were largely maintained in the circulation of aged humans, whereas Th17 cells were decreased. Similar to memTreg cells, the 3 Teff subsets resided primarily in the memory CD4+ T cell compartment. Overall, Treg/Teff ratios were increased in the memory CD4+ T cell compartment of aged individuals when compared to that of young individuals. Finally, the relative increase of memTreg cells in elderly individuals was associated with poor responses to influenza vaccination. Taken together, our findings imply that aging disturbs the balance between Treg cells and Teff cells.

Antibiotic induced intestinal dysbiosis in infant mice impacts CD8+ T cell anti-viral immune function and control of infection (IRC8P.494)

Abstract Infancy and childhood is a critical period for the development of long-term immune function. Normal acquisition of the gastrointestinal (GIT) flora during this period is now appreciated in its role on immune system development and function. Antibiotics cause GIT flora dysbiosis and may alter normal GIT colonization during infancy. Subsequently, immune development and function may also be affected. In this infant mouse model of antibiotic mediated GIT flora dysbiosis, perinatal antibiotic treatment (AT) alters the composition of the GIT flora in mothers and their infants. CD8+ T cells from AT infant mice activated in vitro with cytokines, proliferate, express activation markers, and produce IFN-γ. However, unlike non-antibiotic treated (CTRL) infant mice, AT mice succumb to vaccinia virus infection. AT infant mice survive sub-lethal infection indicating effective primary immune responses to control infection. Interestingly, the expansion of Teff, Tem, and Tcm subsets differs between CTRL and AT sub-lethally infected infant mice. Transfer of OT-I T cells into AT infant mice prior to lethal infection rescues these mice from death. However, expansion of OT-I T cells is limited in AT infant mice and the differential expression of effector and memory cell markers is also recapitulated. These results suggest that dysbiosis during infancy negatively impacts effective adaptive primary immune responses and has potential consequences on memory T cell development.