White blood cells (leucocytes) are colourless cells with a nucleus, found in blood and lymph. Leucocytes are formed in lymph nodes and red bone marrow and are capable of amoeboid movement. They can produce antibodies and move through the walls of vessels to migrate to the sites of injuries, where they surround and isolate dead tissues, foreign bodies and bacteria. These are of two major types, those without granules in the cytoplasm, such as lymphocytes and monocytes (agranulocytes) and those with granular cytoplasm (granulocytes) such as basophils, eosinophils and neutrophils.