CSF2 and infection: In contrast to the SEAP assay, ΔSPI-2 infection of RAW264.7 cells resulted in less IL-1α, IL-6 and GM-CSF cytokine secretion compared to wild type-infected samples at 24 h of infection and no significant differences were observed between wild type SL1344 and ΔsseK23 infected cells (Figure 6).