Distinct characteristics of unique immunoregulatory canine non-conventional TCRαβ CD4CD8α double-negative T cell subpopulations.

Conventional CD4 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)αβ CD4CD8α double-negative (dn) T cells of dogs, a novel FoxP3 Treg-like subset was described that, similar to conventional CD4 Treg cells, is characterized by high expression of CD25. Noteworthy, human and murine TCRαβ regulatory dn T cells lack FoxP3.