Immunomodulatory in vitro effects of oclacitinib on canine T-cell proliferation and cytokine production.

Background: Oclacitinib is a Janus kinase inhibitor used to control pruritus and skin lesions in canine allergic skin disease; its effect on canine T cells is not well-characterized.
Hypothesis/objectives: To evaluate the impact of oclacitinib on cultured T cells using peripheral blood mononuclear cells from dogs.
Animals: Six bluetick coonhounds.
Methods and Materials: Lymphocyte-enriched cells were incubated with or without the T-cell mitogen concanavalin A (Con A), oclacitinib (0.5, 1 or 10 μM), ciclosporin (200 ng/mL), Con A + oclacitinib 1 μM and Con A + ciclosporin. We assessed both T-cell proliferation and the secretion of cytokines.
Results: Ciclosporin and oclacitinib both inhibited the spontaneous proliferation of T cells; this effect was significant only after incubation with oclacitinib at 10 μM. At this concentration, oclacitinib significantly reduced the spontaneous secretion of clonal activator cytokines [interleukin (IL)-2, IL-15], pro-inflammatory cytokines (interferon-gamma (IFN-γ), IL-18) and the regulatory cytokine IL-10; tumour necrosis factor alpha (TNF-α) and IL-6 cytokine production was mildly inhibited. After Con A stimulation, only T cells co-treated with ciclosporin achieved a significant proliferation inhibition and reduction of IL-2, IL-10, IL-15, IL-18, IFN-γ and TNF-α. Surprisingly, oclacitinib at 1 μM (337 ng/mL, corresponding to the oral dosage of 0.4-0.6 mg/kg) did not significantly affect Con A-stimulated T-cell proliferation nor cytokine production (IL-2, IL-10, IL-15, IL-18, IFN-γ and TNF-α).
Conclusions: Although a limited number of dogs were investigated, these preliminary results suggest that oclacitinib appears to have immunosuppressive properties, but only at dosages above those used to treat allergic pruritus in dogs.
(© 2018 ESVD and ACVD.)