Urinary trypsin inhibitor (UTI), also known as ulinastatin, has been reported to protect multiple organs against inflammation- and/or injury-induced dysfunction. In the present study, we aimed to investigate the immunomodulation effects of a recombinant human ulinastatin (urinary trypsin inhibitor, UTI) (rhUTI) on splenic dendritic cells (DCs) in cecal ligation and puncture (CLP)-induced septic mice. CLP mice were treated with rhUTI intramuscularly at 0, 12, and 24 h after procedure. Splenic CD11c DCs were isolated and accessed with flow cytometry for apoptotic or phenotypic analysis. Protein markers and cytokines were determined with Western blotting or ELISA. Treatment with rhUTI could markedly upregulate levels of costimulatory molecules (CD80, CD86) and MHC-II on surface of the splenic DC in CLP mice. The apoptotic rate of splenic DCs was decreased in CLP mice after rhUTI treatment. The survival rate of septic mice was increased after treatment with rhUTI. In addition, protein level of markers in endoplasmic reticulum stress (ERS)-related apoptotic pathways (including GRP78, caspase-12, and CHOP) were obviously down-regulated in the rhUTI-treated group when compared with the CLP group. These results indicate that rhUTI protects CLP-induced sepsis in mice by improving immune response of splenic DCs and inhibiting the excessive ERS-mediated apoptosis.Copyright © 2020 The Authors. Published by Elsevier B.V. All rights reserved.