In vitro evaluation of the effect of a novel immunosuppressive agent, FTY720, on the function of feline neutrophils

Abstract

Objective - To use in vitro assays to evaluate the effects of a novel immunosuppressive agent, FTY720, on biological functions (migration, phagocytosis, and production of reactive-oxygen species [ROS]) of feline peripheral neutrophils and determine the cytotoxic effects of FTY720 on feline peripheral neutrophils. Sample population - Peripheral neutrophils obtained from 8 healthy cats. Procedure - Peripheral neutrophils were isolated from blood sampl es obtained from the 8 cats and exposed to the phosphorylated form of FTY720 (FTY720-P). A fluorescence-based in vitro evaluation of migration was performed. Phagocytosis of microbes and production of ROS were evaluated by use of a 2-color flow cytometry system. Samples of whole blood obtained from the cats were incubated with various concentrations of FTY720-P fluorescein-labeled Staphylococcus aureus, and dihydroethidium. Cytotoxic effects were evaluated by use of propidium iodide staining. Results - Addition of FTY720-P caused a slight non-sig nificant decrease in phagocytosis and production of ROS by feline peripheral neutrophils. Migration activity of feline peripheral neutrophils was significantly increased by the addition of FTY720-P. Addition of FTY720-P at concentrations considered for clinical use did not increase the death rate of feline peripheral neutrophils. Conclusions and clinical relevance - FTY720 does not inhibit critical functions of feline peripheral neutrophils in vitro.