Color enhanced Transmission Electron Micrograph (TEM) showing a white blood cell (blue) from a mouse that has ingested a sperm cell (yellow). White blood cells (WBCs), also called leukocytes or leucocytes, are the cells of the immune system that are involved in protecting the body against both infectious disease and foreign invaders. All white blood cells are produced and derived from a multipotent cell in the bone marrow known as a hematopoietic stem cell. Leukocytes are found throughout the body, including the blood and lymphatic system. All white blood cells have nuclei, which distinguishes them from the other blood cells, the anucleated red blood cells (RBCs) and platelets. The number of leukocytes in the blood is often an indicator of disease, and thus the WBC count is an important subset of the complete blood count. Magnification: 23,000X at 8x10" print size.