TNF and infection: Mononuclear cells isolated from blood and colorectal biopsies in the acute phase of infection (week 3–4 p.i.)and from ileum, jejunum and colorectal tissue at necropsy (chronic phase) were stimulated with PMA/ionomycin to determine the frequency of IL-17 (acute and chronic phase samples) and IFN-γ, IL-2, TNFα and IL-21-producing cell subsets (chronic phase samples).