Immunoglobulin-Like Transcript 5 Inhibits Macrophage-Mediated Bacterial Killing and Antigen Presentation During Sepsis

Abstract

Background: Immunosuppression contributes to the mortality of sepsis. However, the underlying mechanism remains unclear.

Methods: In the present study, we investigated the role of inhibitory receptor immunoglobulin-like transcript 5 (ILT5) in sepsis. We first screened the expression of ILT family members, and we found that ILT5 was dramatically up-regulated in the peripheral blood mononuclear cells from sepsis patients versus healthy donors.

Results: Knockdown of ILT5 by small interfering ribonucleic acid increased bacterial killing and reactive oxygen species production in THP-1 and RAW264.7 cells. Moreover, ILT5-expressing monocytes/macrophages exhibited lower expression of antigen-presenting molecules including major histocompatibility complex-II and CD80. In the in vitro coculture system with monocytes/macrophages, blockage of ILT5 facilitated Th1 proliferation and differentiation of CD4+ T cells. Furthermore, in vivo experiments demonstrated that pretreatment with ILT5 blocking peptide improved the survival and pulmonary pathology of septic mice.

Conclusions: Together, our study identified ILT5 as an immunosuppressive regulator during sepsis, which may provide potential therapeutic strategy for sepsis.

Keywords: antigen presentation; ILT5; Th1 differentiation; bacterial killing immunosuppression; sepsis.