2016 ACVIM Forum Research Abstract Program

Sixteen aged horses (18-27 yrs), including n = 8 PPID horses (mean = 24.5 AE 2.2 yrs) and n = 8 non-PPID horses (mean = 23.1 AE 3.1 yrs) of mixed breeds and sex, were sampled to determine immune function. Heparinized blood was collected aseptically, and PBMCs were isolated, stimulated with Phorbol 12-myristate 13-acetate (PMA), and stained intracellularly for pro-inflammatory cytokines interferon-c (IFNc) and tumor necrosis factor-a (TNFa). Flow cytometry was performed to determine the percent of lymphocytes producing IFNc and TNFa. Real-time polymerase chain reaction (RT-PCR) was used to determine PBMC gene expression of cytokines interleukin (IL)-2, IL-4, IL-6, IFNc, and TNFa. PBMC proliferation was also determined using carboxyfluorescein succinimidyl ester (CFSE) staining and stimulation with various amount of concanavalin A (Con A; 2.5, 5, and 10 L/mL). TRH stimulation testing was performed, in which adrenocorticotropin hormone (ACTH) levels were measured in plasma 10 minutes post (T-10) intravenous administration of TRH (1 mg/mL saline/horse).