leukocytes - defense against foreign cells
Granulocytes. The leukocytes, or white blood cells, defend the body against infecting organisms and foreign agents, both in the tissues and in the bloodstream itself (see immunity).Human blood contains about 5,000 to 10,000 leukocytes per cubic millimeter; the number increases in the presence of infection.his overproduction suppresses the production of normal blood cells. Conversely, a sharp decrease in the number of leukocytes (leukopenia) strips the blood of its defense against infection and is an equally serious condition.