Mature Γδ Research Articles

Association between anti-Anisakis simplex antibodies and interleukin-7 levels

IL-7 is a crucial factor for the development of lymphocytes, and it is absolutely necessary for γδ T cells. Mice deficient in L-7 have a deficit of B and αβ T lymphocytes, and an absence of mature γδ TCR cells. IL-7 is essential for the survival, development and maturation of Schistosoma sp., although its production is associated with protection against intestinal helminths. The presence of anti-Anisakis simplex antibodies, especially IgA, is related to a lower frequency in CD3 + CD56 + αβ + lymphocytes and all subpopulations of γδ T cells. In this work, the relationship of IL-7 with humoral and cellular responses against A. simplex in 100 healthy subjects was studied. We have found significantly higher IL-7 levels in anti-A. simplex IgA-positive subjects (p < 0.001). The positivity of anti-A. simplex IgA was associated with a significant reduction in the frequency of CD3 + αβ+ (p < 0.01), CD3 + CD4 + αβ+, CD3 + CD8 + αβ+, CD3 + CD56 + αβ+, CD3 + γδ+, CD3 + CD4-CD8-γδ+ and CD3 + CD56 + γδ+ (p < 0.05) cells. In the case of NKT cells, this same phenomenon was also associated with IgE positivity. There was a weak inverse correlation (Spearman) of IL-7 levels with the frequencies of CD3 + CD4 + αβ+ (−0.125, p = 0.047), CD3 + CD8 + αβ+ (−0.204, p = 0.032), CD3 + CD56 + αβ+ (−0.247, p = 0.007), CD3 + γδ+ (−0.267, p = 0.007), CD3 + CD4-CD8-γδ+ (−0.266, p = 0.003), and CD3 + CD8 + γδ + (−0.302, p = 0.002) cells. The role of NKT cells in the anti-A. simplex response was confirmed and an association between IL and 7 levels and specific antibodies, especially IgA, was demonstrated. The higher production of IL-7 would represent a compensatory mechanism in response to the reduction in lymphocyte populations associated with the response against this parasite.

RNA m6A demethylase ALKBH5 regulates the development of γδ T cells

γδ T cells are an abundant T cell population at the mucosa and are important in providing immune surveillance as well as maintaining tissue homeostasis. However, despite γδ T cells' origin in the thymus, detailed mechanisms regulating γδ T cell development remain poorly understood. N6-methyladenosine (m6A) represents one of the most common posttranscriptional modifications of messenger RNA (mRNA) in mammalian cells, but whether it plays a role in γδ T cell biology is still unclear. Here, we show that depletion of the m6A demethylase ALKBH5 in lymphocytes specifically induces an expansion of γδ T cells, which confers enhanced protection against gastrointestinal Salmonella typhimurium infection. Mechanistically, loss of ALKBH5 favors the development of γδ T cell precursors by increasing the abundance of m6A RNA modification in thymocytes, which further reduces the expression of several target genes including Notch signaling components Jagged1 and Notch2. As a result, impairment of Jagged1/Notch2 signaling contributes to enhanced proliferation and differentiation of γδ T cell precursors, leading to an expanded mature γδ T cell repertoire. Taken together, our results indicate a checkpoint role of ALKBH5 and m6A modification in the regulation of γδ T cell early development.

γδ Thymocyte Maturation and Emigration in Adult Mice.

Several unique waves of γδ T cells are generated solely in the fetal/neonatal thymus, whereas additional γδ T cell subsets are generated in adults. One intriguing feature of γδ T cell development is the coordination of differentiation and acquisition of effector function within the fetal thymus; however, it is less clear whether this paradigm holds true in adult animals. In this study, we investigated the relationship between maturation and thymic export of adult-derived γδ thymocytes in mice. In the Rag2pGFP model, immature (CD24+) γδ thymocytes expressed high levels of GFP whereas only a minority of mature (CD24-) γδ thymocytes were GFP+ Similarly, most peripheral GFP+ γδ T cells were immature. Analysis of γδ recent thymic emigrants (RTEs) indicated that most γδ T cell RTEs were CD24+ and GFP+, and adoptive transfer experiments demonstrated that immature γδ thymocytes can mature outside the thymus. Mature γδ T cells largely did not recirculate to the thymus from the periphery; rather, a population of mature γδ thymocytes that produced IFN-γ or IL-17 remained resident in the thymus for at least 60 d. These data support the existence of two populations of γδ T cell RTEs in adult mice: a majority subset that is immature and matures in the periphery after thymic emigration, and a minority subset that completes maturation within the thymus prior to emigration. Additionally, we identified a heterogeneous population of resident γδ thymocytes of unknown functional importance. Collectively, these data shed light on the generation of the γδ T cell compartment in adult mice.

Single-cell analysis reveals the origins and intrahepatic development of liver-resident IFN-\u03b3-producing \u03b3\u03b4 T cells

γδ T cells are heterogeneous lymphocytes located in various tissues. However, a systematic and comprehensive understanding of the origins of γδ T cell heterogeneity and the extrathymic developmental pathway associated with liver γδ T cells remain largely unsolved. In this study, we performed single-cell RNA sequencing (scRNA-seq) to comprehensively catalog the heterogeneity of γδ T cells derived from murine liver and thymus samples. We revealed the developmental trajectory of γδ T cells and found that the liver contains γδ T cell precursors (pre-γδ T cells). The developmental potential of hepatic γδ T precursor cells was confirmed through in vitro coculture experiments and in vivo adoptive transfer experiments. The adoptive transfer of hematopoietic progenitor Lin−Sca-1+Mac-1+ (LSM) cells from fetal or adult liver samples to sublethally irradiated recipients resulted in the differentiation of liver LSM cells into pre-γδ T cells and interferon-gamma+ (IFN-γ+) but not interleukin-17a+ (IL-17a+) γδ T cells in the liver. Importantly, thymectomized mouse models showed that IFN-γ-producing γδ T cells could originate from liver LSM cells in a thymus-independent manner. These results suggested that liver hematopoietic progenitor LSM cells were able to differentiate into pre-γδ T cells and functionally mature γδ T cells, which implied that these cells are involved in a distinct developmental pathway independent of thymus-derived γδ T cells.

Deciphering the regulatory landscape of fetal and adult γδ T‐cell development at single‐cell resolution

γδ T cells with distinct properties develop in the embryonic and adult thymus and have been identified as critical players in a broad range of infections, antitumor surveillance, autoimmune diseases, and tissue homeostasis. Despite their potential value for immunotherapy, differentiation of γδ T cells in the thymus is incompletely understood. Here, we establish a high‐resolution map of γδ T‐cell differentiation from the fetal and adult thymus using single‐cell RNA sequencing. We reveal novel sub‐types of immature and mature γδ T cells and identify an unpolarized thymic population which is expanded in the blood and lymph nodes. Our detailed comparative analysis reveals remarkable similarities between the gene networks active during fetal and adult γδ T‐cell differentiation. By performing a combined single‐cell analysis of Sox13, Maf, and Rorc knockout mice, we demonstrate sequential activation of these factors during IL‐17‐producing γδ T‐cell (γδT17) differentiation. These findings substantially expand our understanding of γδ T‐cell ontogeny in fetal and adult life. Our experimental and computational strategy provides a blueprint for comparing immune cell differentiation across developmental stages.

Expression of T-Bet, Eomesodermin, and GATA-3 Correlates With Distinct Phenotypes and Functional Properties in Porcine γδ T Cells.

Unlike mice and humans, porcine γδ T cells represent a prominent subset of T cells in blood and secondary lymphatic organs. GATA-3, T-bet and Eomesodermin (Eomes) are transcription factors with crucial functions in T-cell development and functional differentiation, but their expression has not been investigated in porcine γδ T cells so far. We analyzed the expression of these transcription factors in γδ thymocytes, mature γδ T cells from blood, spleen, lymph nodes, and lung tissue as well as in vitro stimulated γδ T cells on the protein level by flow cytometry. GATA-3 was present in more than 80% of all γδ-thymocytes. Extra-thymic CD2− γδ T cells expressed high levels of GATA-3 in all investigated organs and had a CD8α−/dimCD27+perforin− phenotype. T-bet expression was mainly found in a subset of CD2+ γδ T cells with an opposing CD8αhighCD27dim/−perforin+ phenotype. Eomes+ γδ T cells were also found within CD2+ γδ T cells but were heterogeneous in regard to expression of CD8α, CD27, and perforin. Eomes+ γδ T cells frequently co-expressed T-bet and dominated in the spleen. During aging, CD2−GATA-3+ γδ T cells strongly prevailed in young pigs up to an age of about 2 years but declined in older animals where CD2+T-bet+ γδ T cells became more prominent. Despite high GATA-3 expression levels, IL-4 production could not be found in γδ T cells by intracellular cytokine staining. Experiments with sorted and ConA + IL-2 + IL-12 + IL-18-stimulated CD2− γδ T cells showed that proliferating cells start expressing CD2 and T-bet, produce IFN-γ, but retain GATA-3 expression. In summary, our data suggest a role for GATA-3 in the development of γδ-thymocytes and in the function of peripheral CD2−CD8α−/dimCD27+perforin− γδ T cells. In contrast, T-bet expression appears to be restricted to terminal differentiation stages of CD2+ γδ T cells, frequently coinciding with perforin expression. The functional relevance of high GATA-3 expression levels in extra-thymic CD2− γδ T cells awaits further clarification. However, their unique phenotype suggests that they represent a thymus-derived separate lineage of γδ T cells in the pig for which currently no direct counterpart in rodents or humans has been described.

Variegated gene expression and Sox-13 mediated regulation of WC1, a hybrid PRR/Co-receptor exclusive to memory gd T cells

Abstract γδ T cells have broader reactivity and respond more rapidly compared to αβ T cells which are restricted to peptide bound to MHC. Some γδ T cells bear lineage-specific glycoproteins known as WC1 that are coded by a multigenic family composed of 13 members. Structurally, WC1 molecules have 6–11 SRCR domains, followed by a conserved transmembrane and a variable cytoplasmic tail. γδ T cells expressing these molecules can be further divided into subsets that express either WC1-3 or WC1-4, a dichotomy analogous to CD4 and CD8 molecules and similarly set up in the thymus. While WC1-3+ and WC1-4+ γδ T cells share a restricted repertoire of the γδ TCR genes, expression of WC1-3 vs. WC1-4 determines whether the γδ T cell is activated by Leptospira; reactivity correlates with expression of WC1-3 and the ability of its SRCR domains to bind to Leptospira. ShRNA-mediated knockdown of WC1-3 significantly reduces the ability of WC1-3 expressing γδ T cells to respond to the bacteria, guiding us to a hypothesis that WC1 is essential for recognition of bacterial pathogens by γδ T cells and that the WC1 family members expressed by a particular cell will determine its ability to respond to an infection. Evaluation of WC1 gene expression among individual γδ T cells indicates that WC1-3 and WC1-4 are always expressed reciprocally, establishing functional subsets. These γδ T cell subsets appear to be set in the thymus, alluding to the transcription factor occupancy of WC1-3 vs WC1-4. Occupancy of candidate Sox13 binding sites differ between WC1-3 and WC1-4 loci, suggesting that Sox13 may play an important role in determining the ability of mature γδ T cells to respond to bacteria.

Abstract PR12: Early TCRα expression during T cell development for the generation of enhanced-affinity TCRs for TCR gene therapy.

Abstract Thymic selection eliminates T cells expressing TCRs with a high affinity for self-antigen. However, many of the most promising tumor antigens for T cell-based cancer immunotherapies are unmodified self-antigens. Therefore, tumor-specific T cells often have a low avidity for tumor antigens, thus limiting the efficacy of this approach. TCR gene therapy using TCR genes that have been modified for increased affinity can overcome this limitation. The generation of enhanced affinity TCRs generally involves saturation mutagenesis targeting the complementarity determining regions of the TCR genes to be modified. However, this approach requires considerable trial and error, and is still not always successful at generating a higher affinity TCR without promiscuous off-target activity. We have developed a system for selecting high affinity tumor antigen-specific TCRs from a population of T cells selected by agonist signaling during T cell development in vitro. The αβ/γδ lineage choice is in part dictated by the strength of TCR/pre-TCR signaling during early T cell development, such that the pre-TCR provides a weak signal that drives αβ T cell development while the mature γδ TCR provides a stronger signal that drives γδ T cell development. In TCR transgenic mice, early expression of the transgenic TCRα chain prior to β-selection can also provide a stronger γδ-like signal through the mature αβ TCR, leading to the development of lineage redirected TCRαβ+ CD4/CD8 double negative (DN) γδ wanna-be” cells. The development of these DN TCRαβ+ cells is enhanced in the presence of cognate antigen or TCR crosslinking; suggesting that early expression of an antigen-specific TCRα chain before β-selection could promote the generation of DN TCRαβ+ cells in the presence of antigen, through a process in which the introduced TCRα chain pairs with an endogenous TCRβ chain to produce an αβ TCR with high affinity for the target antigen. To test this hypothesis, the TCRα chain from a tumor antigen-specific TCR was transduced into hematopoietic progenitor cells and a library of TCRβ chains was isolated from the lineage redirected DN TCRαβ+ T cells that developed. Several TCRβchains of varying CDR3 lengths were isolated that confer enhanced affinity for the target antigen when paired with the introduced TCRα chain. This abstract is also presented as Poster A13. Citation Format: Thomas M. Schmitt, Philip D. Greenberg, David H. Aggen, David Kranz, Sebastian Ochsenreither. Early TCRα expression during T cell development for the generation of enhanced-affinity TCRs for TCR gene therapy. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology: Multidisciplinary Science Driving Basic and Clinical Advances; Dec 2-5, 2012; Miami, FL. Philadelphia (PA): AACR; Cancer Res 2013;73(1 Suppl):Abstract nr PR12.

Cytokines and culture medium have a major impact on human in vitro T-cell differentiation

An important proof of principle has been achieved with the development of an in vitro T-cell differentiation assay based on the coculture of hematopoietic progenitors with the OP9-Delta1 stromal cell line. The original murine T cell differentiation assay has since been adapted for human T-cell differentiation, however with lower efficiency. The choice of both medium and cytokines is crucial in this assay, therefore our work has been focused on these two factors. The use of freshly reconstituted medium, the optimization of interleukine-7 (IL-7) concentration, and the addition of stem cell factor (SCF) have allowed to improve the proliferation of progenitors and T-cell precursors as well as the yield of double positive CD4 + CD8+ T cells, and mature γδ and αβ T cells. These optimizations make the OP9-Delta1 system sensitive enough to perform both quantitative and qualitative assays with various type of progenitors, including those transduced by a retroviral vector. The improved OP9-Delta1 assay therefore constitutes an extremely useful test for basic research purposes and for translational medicine.

SCART Scavenger Receptors Identify a Novel Subset of Adult γδ T Cells

Although there has been great progress in the characterization of alphabeta T cell differentiation, selection, and function, gammadelta T cells have remained poorly understood. One of the main reasons for this is the lack of gammadelta T cell-specific surface markers other than the TCR chains themselves. In this study we describe two novel surface receptors, SCART1 and SCART2. SCARTs are related to CD5, CD6, and CD163 scavenger receptors but, unlike them, are found primarily on developing and mature gammadelta T cells. Characterization of SCART2 positive immature and peripheral gammadelta T cells suggests that they undergo lineage specification in the thymus and belong to a new IL-17-producing subset with distinct homing capabilities.

T Cell Receptor δ Gene Rearrangement and T Early α (TEA) Expression in Immature αβ LineageThymocytes: Implications for αβ/γδ Lineage Commitment

Mature T cells comprise two mutually exclusive lineages expressing heterodimeric αβ or γδ antigen receptors. During development, β, γ, and δ genes rearrange before α, and mature γδ cells arise in the thymus prior to αβ cells. The mechanism underlying commitment of immature T cells to the αβ or γδ lineage is controversial. Since the δ locus is located within the α locus, rearrangement of α genes leads to deletion of δ. We have examined the rearrangement status of the δ locus immediately prior to α rearrangement. We find that many thymic precursors of αβ cells undergo VDJδ rearrangements. Furthermore, the same cells frequently coexpress sterile T early α (TEA) transcripts originating 3′ of Cδ and 5′ of the most upstream Jα, thus implying that individual αβ lineage cells undergo sequential VDJδ and VJα rearrangements. Finally, VDJδ rearrangements in immature αβ cells appear to be random, supporting models in which αβ lineage commitment is determined independently of the rearrangement status at the TCR δ locus.