Abstract

(…) Impairment of immune function and inflammatory incidences in marine mammals are generally difficult to detect (King et al. 1996, Zeneto-Savin et al. 1997, Funke et al. 2003). Therefore, markers for inflammation would be helpful to monitor the health status of animals kept in captivity and of free-ranging animals. It is well established that initiation and progression of an immune response are regulated by cytokines (Lucey et al. 1996, Elenkov and Chrousos 1999, Kidd 2003). During an immune reaction, pro- and anti-inflammatory cytokines are distinguished (Tizard 1996, DiPiro 1997). In the beginning of an immune response, proinflammatory cytokines, such as interleukin (IL)-1β, IL-6, IL-8 and tumor necrosis factor (TNF)α, are produced predominantly by macrophages and monocytes and can be used to detect subclinical infections (King et al. 1996, Tizard 1996, DiPiro 1997, Funke et al. 2003). Further progression involves T helper (Th) cells (Lucey et al. 1996, Mosmann and Sad 1996, Elenkov and Chrousos 1999, Singh et al. 1999, Kidd 2003). Th1 cells secrete the proinflammatory cytokines interferon (IFN)γ, IL-2, and TNFβ, which stimulate cell-mediated immunity, whereas Th2 cells produce IL-4, IL-10, IL-6, and IL-13, which inhibit cell-mediated immunity and promote humoral immune responses (Lucey et al. 1996, Mosmann and Sad 1996, Elenkov and Chrousos 1999, Singh et al. 1999, Kidd 2003). Th3 cells mainly produce transforming growth factor (TGF)β, which suppress Th1 and Th2 cells. These cytokines act to downregulate overwhelming immune responses, especially aggressive autoimmune reactions (Weiner 2001, Zheng et al. 2002, Allez and Mayer 2004, Mills 2004, Wahl et al. 2004). The precise role of these cytokines in marine mammals is unclear, although the presence of IL-6 as a marker for inflammation is described (King et al. 1996, Funke et al. 2003). The acute phase proteins (APP) haptoglobin (Hp) and C-reactive protein (CRP) are used as markers for inflammation and stress in veterinary medicine. Correlations with pollutant exposure, declining populations, and inflammation in marine mammals have been described (Eckersall and Conner 1988, Funke et al. 1997,
Zeneto-Savin et al. 1997, Heegaard et al. 1998, Petersen et al. 2002, Beckmen et al. 2003, Murata et al. 2004, Vermeire et al. 2004). Little is known about cytokine expression and Th subpopulations in harbor porpoises (Beineke et al. 2004). The aim of this study, therefore, was to investigate gene expression of the cytokines IL-1β, -2, -4, -6, -10, TNFα, TGFβ, and the APP Hp and CRP in blood samples from two captive harbor porpoises (Phocoena phocoena). (…)