For cytokine analysis, macrophages were infected with Listeria strains at MOI 10:1, centrifuged at 300 g for 2 min and incubated at 37uC for 15 min. Following phagocytosis, monolayers were washed twice followed by incubation in RPMI-1640 supplemented with 10% fetal bovine serum (FBS) and gentamicin (20 mg/mL). Supernatants were collected at various time points, for detection of IFN-b by ELISA. For transcript analysis, macrophages were infected with Listeria strains at MOI 20:1 and incubated at 37uC for 1 h to allow phagocytosis. Monolayers were washed and incubated in DMEM supplemented with 10% FCS and gentamicin (5 mg/mL). After 2 h, medium was changed to DMEM supplemented with 10% FCS and gentamicin (1 mg/mL). Cells were lysed at various time points and RNA collected for qPCR analysis.