IL18 and infection: This is well in line with our previous infection studies in secondary abiotic mice that were deficient in matrix metalloproteinase (MMP) -2 or -9 [24, 36], in cytokines belonging to the IL-23/IL-22/IL-18 axis [32] or in innate immune receptors including Toll-like receptor (TLR) -4 or -9 and respective WT counterparts [8, 32].