Also found in: Dictionary, Thesaurus, Encyclopedia.
white blood cellany of the large unpigmented cells in the blood of vertebrates. There are several types, formed in both lymph glands and bone marrow.
Leucocytes are a primary defence against invading organisms and other foreign material, using two main methods: PHAGOCYTOSIS and the IMMUNE RESPONSE. The leucocyte count is usually around 10 000 cells per mm3 of blood. This, however, is not the total body count, because leucocytes are found as much in tissues such as thymus, spleen and kidney as in blood. The cells generally have a short life span (2 to 14 days) although the antibody-producing types (B-CELLS) tend to last up to 100 days. Compare ERYTHROCYTE. See also individual entries for the cells in Fig. 210.