The Immune Function of Ly6Chi Inflammatory Monocytes During Infection and Inflammation

Monocytes originate from progenitors in bone marrow and circulate through blood vessels and patrol the vascular endothelium or differentiate into mononuclear phagocytes and infiltrate via the bloodstream to peripheral tissues during infection and other inflammatory conditions. Recruitment of inflammatory monocytes is essential for effectively clearance of bacteria, control of Toxoplasma gondii infections and limiting tissue damage. Unexpectedly, Ly6Chi inflammatory monocytes acquire the inflammatory regulatory capacity dual phenotypes during acute infection and inflammation. In addition, inflammatory monocytes can be recruited to tumor sites and inhibit tumor-specific immune defense. Here, we explored the recruitment and characteristics of Ly6Chi inflammatory monocytes and their immune regulatory function in acute inflammation, infection and tumor models. We also contrasted the differences between M2 macrophages and Ly6Chi inflammatory monocytes and, in particular, compared the shared common characteristics between these immune cell types. The Ly6Chi inflammatory monocyte regulatory functions in infectious and inflammatory conditions are the focus of this review.