Cyclosporine is a commonly used immunosuppressive drug in dogs, but dosing is often empirical and based primarily on clinical response. Pharmacokinetic monitoring of blood drug concentrations can be performed, but target blood concentrations for various disease states in dogs are not well described. Pharmacodynamic assays measuring the effects of cyclosporine on target cells are being used to evaluate immunosuppressive effectiveness in humans, but have been minimally explored in veterinary medicine. This dissertation describes the development of pharmacodynamic assays for measuring the effects of cyclosporine on canine T cell cytokine production and surface antigen expression. Incubation with cyclosporine in vitro caused significant suppression of activated T cell production of interleukin-2 (IL-2), IL-4, interferon-gamma (IFN-gamma), CD25, and CD95 measured in peripheral blood mononuclear cells using flow cytometry. IL-2 and IFN-gamma were then evaluated using flow cytometry and quantitative reverse transcription polymerase chain reaction (qRT-PCR) in whole blood incubated with cyclosporine and dexamethasone in vitro. Cyclosporine caused concentration-dependent inhibition of both cytokines, and a greater degree of suppression was noted with qRT-PCR than flow cytometry. Dexamethasone caused concentration-dependent inhibition of IFN-gamma with both methods, but IL-2 reduction was only significant for qRT-PCR. Both methods were then used to evaluate IL-2 and IFN-gamma after administration of high dose oral cyclosporine to dogs. Both qRT-PCR and flow cytometry identified marked cytokine suppression after cyclosporine dosing, but qRT-PCR was uniformly suppressed across the 12-hour dosing interval, while flow cytometry results were significantly higher at trough blood drug concentrations than at peak blood concentrations and subsequent post-dosing time points. Both flow cytometry and qRT-PCR are valid methods for evaluation of T cell cytokine expression in dogs. Further study at lower drug doses is needed to correlate pharmacodynamic results with pharmacokinetic drug concentrations, and to confirm the best method for cytokine monitoring. Studies in clinic patients are also needed to determine the level of cytokine suppression associated with clinical effectiveness in different disease states. Pharmacodynamic evaluation of cyclosporine’s effects shows promise, and may allow for more individualized dosing of cyclosporine in dogs.

Rates of immune-mediated diseases (IMDs) have rapidly increased. Although the exact etiology has not yet been fully elucidated, disruptions to the microbiome has been proposed as a potential mechanism. We conducted a retrospective, longitudinal, birth cohort study utilizing electronic health records (EHR) to investigate the association between early life antibiotic exposure and the risk of developing juvenile idiopathic arthritis (JIA), pediatric psoriasis, or type 1 diabetes. Incident rate ratios (IRR) were estimated using modified Poisson regression models and adjusted for significant confounders. Children exposed to two or more antibiotics prior to 12 months of age had a 69% increased risk of developing JIA (1.69 IRR, 95% CI [1.04-2.73]), which rose to 97% when exposed prior to 6 months (1.97 IRR, 95% CI [1.11-3.49]). Children exposed to a penicillin antibiotic had a 62% increase in risk for psoriasis (1.62 IRR, 95% CI [1.06-2.49]), which rose slightly to 64% when exposure occurred between 6 and 12 months of age [(1.64 IRR, 95% CI [1.04-2.59]). We found a moderate to strong association between early antibiotic exposure and risk for JIA and psoriasis when exposure was examined by age, frequency, and type of antibiotic, but not for type 1 diabetes. Potential interactions effects between infection and antibiotics with an increased susceptibility to early life infections among children with an IMD was also observed. Overall, children exposed to antibiotics at an early age have an increased probability of developing an IMD after 12 months of age. However, alternative explanations for this association should be considered. / Public Health