BACKGROUND: ILT4(+) monocytes seem to be associated with poor prognosis of sepsis in humans, but the exact mechanisms are unknown. This study aimed to examine the biological behaviors and effects of immunoglobulin-like transcript-4 (ILT4) levels on monocytes during sepsis and on the prognosis of sepsis. METHODS: ILT4(+/+) (WT) and ILT4-knockout (ILT4(-/-)) male BALB/c mice were used for sepsis modeling using cecal ligation puncture (CLP). Flow cytometry was used to measure the levels of ILT4 and major histocompatibility complex class II (MHC-II) on peripheral blood monocytes 24?h after CLP. ELISA was used to measure the serum levels of tumor necrosis factor-alpha (TNF-α), interleukin (IL)-1β, IL-6, and IL-12 at 0, 6, 12, and 24?h after CLP. Survival and prognosis were monitored over the course of 168?h. RESULTS: ILT4 was highly expressed in peripheral blood monocytes of septic mice 24?h after CLP (1292.00?±?143.70 vs. 193.50?±?52.54, p?