The multifactorial roles of IL-34 in immune responses

Abstract

Interleukin 34 (IL-34), a newly identified interleukin that is functionally similar to macrophage colony-stimulating factor (M-CSF), stimulates and persists the survival, differentiation, migration and function of various myeloid mononuclear cells and macrophages. These cells express IL-34 receptor, colony-stimulating factor 1 receptor (CSF1R, CD115). IL-34 forcefully combines to CSF1R and then recruits macrophage and monocyte which secret TNF and IL-6 to initiate the innate or adaptive immune responses. The high serum level of IL-34 was observed in many inflammatory and autoimmune diseases that are linked to the unique pro-inflammatory role of IL-34 in immune responses. In addition, IL-34 is considered to be a pro-inflammatory cytokine in anti-virus infection. Nonetheless, IL-34 also exerts an immunosuppressive reinforcement expressed in Treg that involves in the immunoregulatory role. Here, we conduct a systematic review to update the roles of IL-34 in immune responses.