NLRC4 and infection: NAIP-/- and NLRC4-/- THP-1s treated with CASP5 siRNA showed a slight but significant decrease in IL-1β secretion following CASP5 siRNA treatment, but not CASP4 siRNA treatment, compared to control siRNA-treated cells following WT Stm infection (Fig 4A, 4B, 4D and 4E).