ACTA1 and infection: To exclude a significant role of attached or intraendosomal Listeria, Cxcl-2+ and GFP+ epithelial cells were quantified after infection with Listeria expressing GFP either constitutively under control of the superoxide dismutase promoter (Psod-gfp) or inducible under the control of the actA promoter (PactA-gfp) (Table 1).