Promyelocyte blood cell, light micrograph. This blood cell (centre) is a precursor for a type of white blood cell called a granulocyte, formed by granulopoiesis in the bone marrow. Granulocytes, like all white blood cells, are part of the body's immune system. They are involved in the body's immune response, and contain granules with enzymes used to destroy pathogens. The surrounding cells are mostly red blood cells. The stain used here is the May-Grunwald-Giemsa (MGG) stain. The other cells (grey) are red blood cells. Magnification: x1430 when printed at 10 centimetres across.