CASP1 and infection: Secretion of both cytokines is significantly diminished during infection with L. pneumophila lacking DotA, an essential component of the T4SS (ΔdotA Lp), and is significantly diminished in caspase-1/caspase-11-deficient (Casp1−/−Casp11−/−) macrophages as well (Figure 1A).