The correct answer is leukocytes.
Leukocytes also called white blood cells refers to the cells of the immune system, which takes part in safeguarding the body against both the foreign invaders and infectious diseases.
All the white blood cells are obtained and generated from the multipotent cells in the bone marrow called hematopoietic stem cells. Leukocytes are found all over the body, including the lymphatic system and the blood.
