Differences in immune cell function between tuberculosis positive and negative Asian elephants

Summary Tuberculosis is an important health concern for Asian elephant ( Elephas maximus ) populations worldwide, however, mechanisms underlying susceptibility to Mycobacterium tuberculosis are unknown. Proliferative responses assessed via brominated uridine incorporation and cytokine expression measured by real-time RT-PCR were evaluated in peripheral blood mononuclear cell (PBMC) cultures from 8 tuberculosis negative and 8 positive Asian elephants. Cultures were stimulated with Mycobacterium bovis purified protein derivative (PPD-B), M. tuberculosis culture filtrate protein (CFP)-10, and Mycobacterium avium PPD (PPD-A). Following stimulation with PPD-B, proliferation was higher ( α  = 0.005) in positive samples; no significant differences were detected following CFP-10 or PPD-A stimulation. Tumor necrosis factor (TNF)-α, interleukin (IL)-12, and interferon (IFN)-γ expression was greater in samples from positive elephants following stimulation with PPD-B ( α  = 0.025) and CFP-10 ( α  = 0.025 TNF-α and IL-12; α  = 0.005 IFN-γ). Stimulation with PPD-A also produced enhanced IL-12 expression in positive samples ( α  = 0.025). Findings suggested that differences in immune cell function exist between tuberculosis positive and negative elephants. Proliferative responses and expression of TNF-α, IL-12, and IFN-γ in response to stimulation with PPD-B and CFP-10 differ between tuberculosis positive and negative elephants, suggesting these parameters may be important to tuberculosis immunopathogenesis in this species.