Myeloid cells are a group of immune cells that belong to the innate immune system, consisting of cell types known as monocytes, macrophages, dendritic cells, and granulocytes. These cells serve various essential roles in the body’s immune system. They are critically involved in the regulation of T cell responses, bridging our body’s innate and adaptive immune systems. Due to various immunosuppressive factors produced in the tumor microenvironment, the normal function of these cells can be inhibited, limiting their ability to create a productive anti-tumor immune response.
When functioning properly, myeloid cells can stimulate anti-tumor effects in the body, including direct tumor cell killing as well as activation of tumor-specific T cells to support durable anti-tumor immune responses and immunological memory. Activated myeloid cells also secrete pro-inflammatory chemokines and cytokines that recruit additional immune effector cells and help convert immunologically “cold” tumors into “hot” tumors. As such, these normally tumor-supportive myeloid cells can be converted to tumor-destructive myeloid cells that amplify innate and adaptive immune responses, leading to productive anti-tumor immunity.