B. vulgatus mpk mono-colonized mice only showed expression of IL-6 mRNA [18], whereas E. coli mpk mono-colonized mice, prone to develop colitis and SPF IL-2−/−-mice already suffering from colitis, revealed high levels of IL-1α, IL-1β, TNF-α, IFN-γ, IL-10 and IL-6 mRNA in the intestine [3]. Here, IL1B is linked to colitis.