Phenotypic and Functional Characterization of Freshly Isolated and Expanded Canine Regulatory T Cells

Abstract

Regulatory T cells (T_reg) are CD4⁺ T lymphocytes with constitutive expression of CD25 and FOXP3, as well as the ability to modulate cellular immune responses. In this study, the phenotypic characteristics, function and feasibility of enrichment and expansion of canine T_reg were examined. Canine peripheral blood mononuclear cells were isolated and enriched by labelling of CD25, and expansion of T_reg was achieved by adding interleukin (IL)-2 for 1 week. Phenotypic and functional analyses of T_reg were performed prior to and after expansion. Canine T_reg could be phenotypically characterized by CD4, CD25, and FOXP3 expression. Isolation and enrichment of canine T_reg is possible, but high purities are difficult to achieve without significant cell loss. Expansion of canine T_reg was possible by adding IL-2 without other growth factors. Higher initial cell numbers seeded allow more substantial T_reg expansion in vitro. Canine T_reg have the potential to suppress proliferation of effector T cells (T_eff). By adding expanded T_reg, a higher capability for suppressing T_eff could be shown in comparison with freshly isolated T_reg. Enrichment and expansion of canine T_reg is feasible, and canine T_reg had similar characteristics to T_reg from other species.