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Karwig L, Moore PF, Alber G, Eschke M. Distinct characteristics of unique immunoregulatory canine non-conventional TCRαβ pos CD4 negCD8α neg double-negative T cell subpopulations. Front Immunol 2024; 15:1439213. [PMID: 39185407 PMCID: PMC11341405 DOI: 10.3389/fimmu.2024.1439213] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2024] [Accepted: 07/12/2024] [Indexed: 08/27/2024] Open
Abstract
Conventional CD4pos regulatory T (Treg) cells characterized by expression of the key transcription factor forkhead box P3 (FoxP3) are crucial to control immune responses, thereby maintaining homeostasis and self-tolerance. Within the substantial population of non-conventional T cell receptor (TCR)αβpos CD4negCD8αneg double-negative (dn) T cells of dogs, a novel FoxP3pos Treg-like subset was described that, similar to conventional CD4pos Treg cells, is characterized by high expression of CD25. Noteworthy, human and murine TCRαβpos regulatory dn T cells lack FoxP3. Immunosuppressive capacity of canine dn T cells was hypothesized based on expression of inhibitory molecules (interleukin (IL)-10, cytotoxic T-lymphocyte associated protein 4, CTLA4). Here, to verify their regulatory function, the dnCD25pos (enriched for FoxP3pos Treg-like cells) and the dnCD25neg fraction, were isolated by fluorescence-activated cell sorting from peripheral blood mononuclear cells (PBMC) of Beagle dogs and analyzed in an in vitro suppression assay in comparison to conventional CD4posCD25pos Treg cells (positive control) and CD4posCD25neg T cells (negative control). Canine dnCD25pos T cells suppressed the Concanavalin A-driven proliferation of responder PBMC to a similar extent as conventional CD4posCD25pos Treg cells. Albeit to a lesser extent than FoxP3-enriched dn and CD4posCD25pos populations, even dnCD25neg T cells reduced the proliferation of responder cells. This is remarkable, as dnCD25neg T cells have a FoxP3neg phenotype comparable to non-suppressive CD4posCD25neg T cells. Both, CD25pos and CD25neg dn T cells, can mediate suppression independent of cell-cell contact and do not require additional signals from CD4posCD25neg T cells to secrete inhibitory factors in contrast to CD4posCD25pos T cells. Neutralization of IL-10 completely abrogated the suppression by dnCD25pos and CD4posCD25pos Treg cells in a Transwell™ system, while it only partially reduced suppression by dnCD25neg T cells. Taken together, unique canine non-conventional dnCD25pos FoxP3pos Treg-like cells are potent suppressor cells in vitro. Moreover, inhibition of proliferation of responder T cells by the dnCD25neg fraction indicates suppressive function of a subset of dn T cells even in the absence of FoxP3. The identification of unique immunoregulatory non-conventional dn T cell subpopulations of the dog in vitro is of high relevance, given the immunotherapeutic potential of manipulating regulatory T cell responses in vivo.
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Affiliation(s)
- Laura Karwig
- Institute of Immunology/Molecular Pathogenesis, Center for Biotechnology and Biomedicine, Faculty of Veterinary Medicine, Leipzig University, Leipzig, Germany
| | - Peter F. Moore
- Department of Veterinary Pathology, Microbiology and Immunology, School of Veterinary Medicine, University of California, Davis, Davis, CA, United States
| | - Gottfried Alber
- Institute of Immunology/Molecular Pathogenesis, Center for Biotechnology and Biomedicine, Faculty of Veterinary Medicine, Leipzig University, Leipzig, Germany
| | - Maria Eschke
- Institute of Immunology/Molecular Pathogenesis, Center for Biotechnology and Biomedicine, Faculty of Veterinary Medicine, Leipzig University, Leipzig, Germany
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Protschka M, Di Placido D, Moore PF, Büttner M, Alber G, Eschke M. Canine peripheral non-conventional TCRαβ + CD4 -CD8α - double-negative T cells show T helper 2-like and regulatory properties. Front Immunol 2024; 15:1400550. [PMID: 38835756 PMCID: PMC11148280 DOI: 10.3389/fimmu.2024.1400550] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2024] [Accepted: 04/29/2024] [Indexed: 06/06/2024] Open
Abstract
The dog is an important companion animal and also serves as model species for human diseases. Given the central role of T cells in immune responses, a basic understanding of canine conventional T cell receptor (TCR)αβ+ T cells, comprising CD4+ single-positive (sp) T helper (Th) and CD8α+ sp cytotoxic T cell subsets, is available. However, characterization of canine non-conventional TCRαβ+ CD4+CD8α+ double-positive (dp) and TCRαβ+ CD4-CD8α- double-negative (dn) T cells is limited. In this study, we performed a comprehensive analysis of canine dp and dn T cells in comparison with their conventional counterparts. TCRαβ+ T cells from peripheral blood of healthy dogs were sorted according to their CD4/CD8α phenotype into four populations (i.e. CD4+ sp, CD8α+ sp, dp, and dn) and selected surface markers, transcription factors and effector molecules were analyzed ex vivo and after in vitro stimulation by RT-qPCR. Novel characteristics of canine dp T cells were identified, expanding the previously characterized Th1-like phenotype to Th17-like and Th2-like properties. Overall, mRNA expression of various Th cell-associated cytokines (i.e. IFNG, IL17A, IL4, IL13) in dp T cells upon stimulation highlights their versatile immunological potential. Furthermore, we demonstrated that the CD4-CD8α- dn phenotype is stable during in vitro stimulation. Strikingly, dn T cells were found to express highest mRNA levels of type 2 effector cytokines (IL4, IL5, and IL13) upon stimulation. Their strong ability to produce IL-4 was confirmed at the protein level. Upon stimulation, the percentage of IL-4-producing cells was even higher in the non-conventional dn than in the conventional CD4+ sp population. Constitutive transcription of IL1RL1 (encoding IL-33Rα) further supports Th2-like properties within the dn T cell population. These data point to a role of dn T cells in type 2 immunity. In addition, the high potential of dn T cells to transcribe the gene encoding the co-inhibitory receptor CTLA-4 and to produce the inhibitory cytokine IL-10 indicates putative immunosuppressive capacity of this population. In summary, this study reveals important novel aspects of canine non-conventional T cells providing the basis for further studies on their effector and/or regulatory functions to elucidate their role in health and disease.
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MESH Headings
- Animals
- Dogs
- Receptors, Antigen, T-Cell, alpha-beta/genetics
- Receptors, Antigen, T-Cell, alpha-beta/immunology
- Receptors, Antigen, T-Cell, alpha-beta/metabolism
- Th2 Cells/immunology
- CD8 Antigens/metabolism
- CD8 Antigens/immunology
- Cytokines/metabolism
- CD4 Antigens/metabolism
- CD4 Antigens/immunology
- T-Lymphocyte Subsets/immunology
- T-Lymphocyte Subsets/metabolism
- T-Lymphocytes, Regulatory/immunology
- T-Lymphocytes, Regulatory/metabolism
- Immunophenotyping
- Male
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Affiliation(s)
- Martina Protschka
- Institute of Immunology, Center for Biotechnology and Biomedicine, Faculty of Veterinary Medicine, Leipzig University, Leipzig, Germany
| | - Daniela Di Placido
- Institute of Immunology, Center for Biotechnology and Biomedicine, Faculty of Veterinary Medicine, Leipzig University, Leipzig, Germany
| | - Peter F. Moore
- Department of Pathology, Microbiology and Immunology, School of Veterinary Medicine, University of California, Davis, Davis, CA, United States
| | - Mathias Büttner
- Institute of Immunology, Center for Biotechnology and Biomedicine, Faculty of Veterinary Medicine, Leipzig University, Leipzig, Germany
| | - Gottfried Alber
- Institute of Immunology, Center for Biotechnology and Biomedicine, Faculty of Veterinary Medicine, Leipzig University, Leipzig, Germany
| | - Maria Eschke
- Institute of Immunology, Center for Biotechnology and Biomedicine, Faculty of Veterinary Medicine, Leipzig University, Leipzig, Germany
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Rabiger FV, Rothe K, von Buttlar H, Bismarck D, Büttner M, Moore PF, Eschke M, Alber G. Distinct Features of Canine Non-conventional CD4 -CD8α - Double-Negative TCRαβ + vs. TCRγδ + T Cells. Front Immunol 2019; 10:2748. [PMID: 31824515 PMCID: PMC6883510 DOI: 10.3389/fimmu.2019.02748] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2019] [Accepted: 11/11/2019] [Indexed: 01/01/2023] Open
Abstract
The role of conventional TCRαβ+CD4+ or TCRαβ+CD8α+ single-positive (sp) T lymphocytes in adaptive immunity is well-recognized. However, non-conventional T cells expressing TCRαβ or TCRγδ but lacking CD4 and CD8α expression [i.e., CD4−CD8α− double-negative (dn) T cells] are thought to play a role at the interface between the innate and adaptive immune system. Dn T cells are frequent in swine, cattle or sheep and predominantly express TCRγδ. In contrast, TCRγδ+ T cells are rare in dogs. In this study, we identified a high proportion of canine dn T cells in the TCRαβ+ T cell population of PBMC, lymphatic and non-lymphatic organs. In PBMC, the frequency of this T cell subpopulation made up one third of the frequency of TCRαβ+CD4+ sp, and almost half of the frequency of TCRαβ+CD8α+ sp T cells (i.e., ~15% of all TCRαβ+ T cells). Among TCRαβ+CD4−CD8α− dn T cells of PBMC and tissues, FoxP3+ cells were identified indicating regulatory potential of this T cell subset. 80% of peripheral blood FoxP3+TCRαβ+CD4−CD8α− dn T cells co-expressed CD25, and, interestingly, also the FoxP3-negative TCRαβ+CD4−CD8α− dn T cells comprised ~34% CD25+ cells. Some of the FoxP3-positive TCRαβ+CD4−CD8α− dn T cells co-expressed GATA-3 suggesting stable function of regulatory T cells. The frequency of GATA-3 expression by FoxP3−TCRαβ+CD4−CD8α− dn T cells was even higher as compared with TCRαβ+CD4+ sp T cells (20.6% vs. 11.9%). Albeit lacking FoxP3 and CD25 expression, TCRγδ+CD4−CD8α− dn T cells also expressed substantial proportions of GATA-3. In addition, TCRαβ+CD4−CD8α− dn T cells produced IFN-γ and IL-17A upon stimulation. T-bet and granzyme B were only weakly expressed by both dn T cell subsets. In conclusion, this study identifies two dn T cell subsets in the dog: (i) a large (~7.5% in Peyer's patches, ~15% in lung) population of TCRαβ+CD4−CD8α− dn T cells with subpopulations thereof showing an activated phenotype, high expression of FoxP3 or GATA-3 as well as production of IFN-γ or IL-17A and (ii) a small TCRγδ+CD4−CD8α− dn T cell subset also expressing GATA-3 without production of IFN-γ or IL-17A. It will be exciting to unravel the function of each subset during immune homeostasis and diseases of dogs.
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Affiliation(s)
- Friederike V Rabiger
- Institute of Immunology/Molecular Pathogenesis, Center for Biotechnology and Biomedicine, College of Veterinary Medicine, University of Leipzig, Leipzig, Germany
| | - Kathrin Rothe
- Institute of Immunology/Molecular Pathogenesis, Center for Biotechnology and Biomedicine, College of Veterinary Medicine, University of Leipzig, Leipzig, Germany
| | - Heiner von Buttlar
- Institute of Immunology/Molecular Pathogenesis, Center for Biotechnology and Biomedicine, College of Veterinary Medicine, University of Leipzig, Leipzig, Germany
| | - Doris Bismarck
- Institute of Immunology/Molecular Pathogenesis, Center for Biotechnology and Biomedicine, College of Veterinary Medicine, University of Leipzig, Leipzig, Germany
| | - Mathias Büttner
- Institute of Immunology/Molecular Pathogenesis, Center for Biotechnology and Biomedicine, College of Veterinary Medicine, University of Leipzig, Leipzig, Germany
| | - Peter F Moore
- Department of Pathology, Microbiology and Immunology, School of Veterinary Medicine, University of California, Davis, Davis, CA, United States
| | - Maria Eschke
- Institute of Immunology/Molecular Pathogenesis, Center for Biotechnology and Biomedicine, College of Veterinary Medicine, University of Leipzig, Leipzig, Germany
| | - Gottfried Alber
- Institute of Immunology/Molecular Pathogenesis, Center for Biotechnology and Biomedicine, College of Veterinary Medicine, University of Leipzig, Leipzig, Germany
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