A tissue-specific cytokine response was observed after experimental infection of chickens with C. jejuni 81116, in which an early increase in IL-6 mRNA expression was detected in cecal tissue and the spleen, and a delayed IL-1β mRNA expression increase only in the spleen [24].The upregulation of IL-6 mRNA expression at four hours post C. jejuni 0097 inoculation (Fig. 5b) suggests a correlation with the invasion index at three hpi (Fig. 3b), which was previously described for IL-8 and C. jejuni 81–176 after infection of human embryonic INT407 intestinal cells [36]. Here, IL6 is linked to infection.