TNF and Sepsis: Despite this delay in cerebral microbial invasion by E. coli in neonatal septic mice, TNF concentrations were already elevated after 4 h of sepsis and did not significantly change with further progression of sepsis, indicating that systemic pro-inflammatory cytokines such as TNF can enter cerebral tissue in the early stages of sepsis while the blood-brain barrier might still provide protection against invading microorganisms.