Variations of Cytokine Expression and the Impact of Stress and Infection in Harbour Seals (Phoca vitulina) of the North Sea
IAAAM Archive
Sonja Fonfara1; Ursula Siebert1; Andreas Prange2; Franciscus Colijn2
1GKSS Research Centre, Research- and Technology Centre Westcoast (FTZ), University of Kiel, Büsum, Germany; 2GKSS Research Centre, Institute for Coastal Research, Geesthacht, Germany


Cytokines as mediators of the immune response have been described as indicators of infections and stress. Several natural aspects, like age, sex of animals and season, and outside factors, like pathogens and stress, influence the immune system.

Our study comprised two investigation groups: free-ranging seals of the North Sea and newborn abandoned seal pups. To study the impact of natural and external factors on cytokine expression, we investigated blood samples from free-ranging seals taken during 4 wild-catch campaigns on a sandbank of the North Sea and on Rømø in spring and fall of 2004 and 2005. Furthermore, to get information about the development of cytokine expression during the first months of life, we analysed blood samples from newborn pups found at the coast of the German North Sea and rehabilitated in the Seal Station Friedrichskoog.

We analysed the expression of pro-inflammatory cytokines Interleukin-(IL)-1β, IL-2, -6, -8, -12, interferon(IFN)-γ and tumour necrosis factor-(TNF)-α, and anti-inflammatory cytokines IL-4, -10, and transforming growth factor-(TGF)-β using real time RT-PCR. Additionally, we measured Cortisol as indicator for the stress impact.

We found differences in cytokine expression between the wild-catch campaigns, and between juvenile and adult seals. Juvenile seals were more sensible to the stress impact of the catch, which is shown by higher Cortisol levels and resulted in an increase of cytokine mRNA levels, which implies an activation of the immune system.

The cytokine expression of the newborn pups, who were weak and diseased when they arrived in the seal station, changed from higher pro-inflammatory cytokine expression in the beginning of the rehabilitation towards an increase of anti-inflammatory cytokines at the end of the rehabilitation.

In the investigated seals we found seasonal and age dependent differences in cytokine expression and changes induced by stress and pathogens, which indicate that cytokine expression is useful to analyse the function of the immune response.

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Sonja Fonfara

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