1. Distinct characteristics of unique immunoregulatory canine non-conventional TCRαβpos CD4negCD8αneg double-negative T cell subpopulations.
- Author
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Karwig, Laura, Moore, Peter F., Alber, Gottfried, and Eschke, Maria
- Subjects
REGULATORY T cells ,MONONUCLEAR leukocytes ,SUPPRESSOR cells ,FORKHEAD transcription factors ,T cells - Abstract
Conventional CD4
pos 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 CD4neg CD8αneg double-negative (dn) T cells of dogs, a novel FoxP3pos Treglike 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 CD4pos CD25pos Treg cells (positive control) and CD4pos CD25neg T cells (neg ative control). Canine dnCD25pos T cells suppressed the Concanavalin A-driven proliferation of responder PBMC to a similar extent as conventional CD4pos CD25pos Treg cells. Albeit to a lesser extent than FoxP3-enriched dn and CD4pos CD25pos 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 CD4pos CD25neg T cells. Both, CD25pos and CD25neg dn T cells, can mediate suppression independent of cell-cell contact and do not require additional signals from CD4pos CD25neg T cells to secrete inhibitory factors in contrast to CD4pos CD25pos T cells. Neutralization of IL-10 completely abrogated the suppression by dnCD25pos and CD4pos CD25pos Treg cells in a Transwell™ system, while it only partially reduced suppression by dnCD25neg T cells. Taken together, unique canine nonconventional 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 nonconventional 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. [ABSTRACT FROM AUTHOR]- Published
- 2024
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