Monocytes are unique in that they are partially differentiated white cells, meaning they are not fully mature. They are stored in the lymph system, circulate in the blood and migrate to tissues throughout the body, where they mature into one of two types of cells: macrophages or dendritic white cells. Macrophages ingest and break down both invading microbes as well as infected human cells. Dendritic white cells act like messengers taking the broken down antigen material and presenting it to other white cells, typically B-cells, which will identify the antigen and then trigger a chain reaction that helps activate T-cells.