Oclacitinib modulates IL-2 driven T-cell activation through CD25 regulation: A comparative analysis with prednisolone.

Canine Atopic Dermatitis is a T-cell mediated allergic response, with T-cells contributing to skin inflammation through a complex interplay of cytokines and chemokines. Parallels between human AD and canine AD are well-established, supported by transcriptomic and immunologic data that highlight the critical contributions of T-cell subsets to disease progression. To support translational research and therapeutic evaluation, we developed a high-purity isolation protocol for canine T-cells and characterized their proliferation, activation, and cytokine production in response to clinically relevant concentrations of oclacitinib (OM) and prednisolone. Robust T-cell proliferation and activation were achieved in vitro using bead-bound CD86 and plate-bound anti-CD3 with IL-2 supplementation. T-cells treated with OM exhibited dose-dependent reductions in CD25 + T-cell frequency and CD25 expression, particularly in highly proliferative cells. Conversely, prednisolone-treated T-cells closely resembled controls, with progressive increases in CD25 expression and CD25 + cell percentages across divisions. OM also showed a trend toward reduced secretion of IL-8, KC-like, and IL-10, while neither drug significantly affected TNFα, GM-CSF secretion, or cell viability. These findings demonstrate distinct immunomodulatory effects of OM and prednisolone on canine T-cell activation and effector function and establish a robust in vitro platform for future assessment of immune-modulating agents in canine models.