TNF and infection: For the last group of cytokines, i.e. GM-CSF, IL-1β, IL-8, TNFα and IL-23α, the exposure of PAMs to wild type S. Typhimurium significantly increased their transcription and transcription of these cytokines was further significantly increased in PAMs infected with the ΔSPI1 mutant, both 4 and 24 h post infection (Table 2).