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 and limited in 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, and transform into cells that activate tumor-specific T cells that are critical to direct tumor cell killing and immunological memory. Activated myeloid cells also secrete pro-inflammatory chemokines and cytokines that help convert immunologically “cold” tumors into “hot” tumors. As such, these tumor-supportive myeloid cells are converted to tumor-destructive myeloid cells, further amplifying the innate and adaptive immune responses, leading to a productive anti-tumor immune response.