Endotoxin Tolerant Dendritic Cells Suppress Inflammatory Responses in Splenocytes via Interleukin-1 Receptor Associated Kinase (IRAK)-M and Programmed Death-Ligand 1 (PDL-1).

BACKGROUND Sepsis causes the highest mortality in non-cardiovascular intensive care units worldwide. Recent research has demonstrated that the late phase of sepsis, characterized as septic immunosuppression, is the central pathophysiological mechanism of immune dysfunction. Investigating the suppressive mechanism of immune cells may identify possible targets for therapy. MATERIAL AND METHODS We used LPS 2-hit model for dendritic cells (DCs) to establish endotoxin tolerance, and co-cultured with splenocytes. Co-culture responses and gene expressions were evaluated. RESULTS Endotoxin tolerant DCs showed irresponsiveness in pro-inflammatory cytokine production and expressed negative regulator genes of inflammation. When co-cultured with splenocytes, suppression of inflammatory responses and T cells apoptosis were observed with elevated expression of IRAK-M and PDL-1, and interference and neutralization of these 2 molecules led to partly reversed suppression of inflammation. CONCLUSIONS Our research found direct regulation of endotoxin tolerant DCs to other immune cells and suggested a possible mechanism via IRAK-M and PDL-1. This may inform research on septic immunosuppression and suggests possible therapeutic targets for sepsis.