Soluble CD4 effectively prevents excessive TLR activation of resident macrophages in the onset of sepsis.

T lymphopenia, occurring in the early phase of sepsis in response to systemic inflammation, is commonly associated with morbidity and mortality of septic infections. We have previously shown that a sufficient number of T cells is required to constrain Toll-like receptors (TLRs) mediated hyperinflammation. However, the underlying mechanisms remains unsolved. Herein, we unveil that CD4+ T cells engage with MHC II of macrophages to downregulate TLR pro-inflammatory signaling. We show further that the direct contact between CD4 molecule of CD4+ T cells or the ectodomain of CD4 (soluble CD4, sCD4), and MHC II of resident macrophages is necessary and sufficient to prevent TLR4 overactivation in LPS and cecal ligation puncture (CLP) sepsis. sCD4 serum concentrations increase after the onset of LPS sepsis, suggesting its compensatory inhibitive effects on hyperinflammation. sCD4 engagement enables the cytoplasmic domain of MHC II to recruit and activate STING and SHP2, which inhibits IRAK1/Erk and TRAF6/NF-κB activation required for TLR4 inflammation. Furthermore, sCD4 subverts pro-inflammatory plasma membrane anchorage of TLR4 by disruption of MHC II-TLR4 raft domains that promotes MHC II endocytosis. Finally, sCD4/MHCII reversal signaling specifically interferes with TLR4 but not TNFR hyperinflammation, and independent of the inhibitive signaling of CD40 ligand of CD4+ cells on macrophages. Therefore, a sufficient amount of soluble CD4 protein can prevent excessive inflammatory activation of macrophages via alternation of MHC II-TLR signaling complex, that might benefit for a new paradigm of preventive treatment of sepsis.

[SNP discovery by F-CSGE in the coding region of mitochondrial DNA in wild house mice from Shanghai suburb].

This study was performed to discover SNPs for genetic polymorphism analysis of mitochondrial DNA from wild house mice. Universal primer florescent PCR, fluorescence-based conformation sensitive gel electrophoresis (F-CSGE) and DNA sequencing were conducted to analyze the coding region of mitochondrial DNA. Different types of unknown mutations were recorded by variable F-CSGE patterns without false positive. Twenty-four SNPs, sixteen of which were first discovered in the coding region of mitochondrial DNA, were found in 64 wild house mice from 4 districts in Shanghai. Therefore, F-CSGE was proved to be powerful technique for SNP discovery in the coding region mitochondrial DNA. The novel SNPs can be used as molecular markers to analyze population structure and genetic polymorphisms of the wild house mice in Shanghai.