NOD2 and infection: Several of the identified genes are associated with Nod-like receptor signaling and activation of inflammasome complexes, such as Casp1, Casp9, and Nod2. Age and infection were found to be statistically associated with five genes, RIG-I, IFNAR1, IL-1β, OPN, and TLR8 and relative gene expressions from young and aged mice show age-related differences in the gene induction on day 3, when the change in ΔCt and subsequent relative gene expression was found to be statistically significant, often with contrasting trends between mock and 3 dpi (Fig. 4B).