White blood cell

White blood cells (scientific name leukocytes), also called immune cells or immunocytes, are <a href="/facts/Cell_(biology)/bLM9UQvy">cells</a> of the <a href="/facts/Immune_system/HRCTf1pb">immune system</a> that are involved in protecting the body against both <a href="/facts/Infectious_disease/182XrncP">infectious disease</a> and foreign entities. White blood cells are generally larger than <a href="/facts/Red_blood_cells/Kggpq8Jh">red blood cells</a>. They include three main subtypes: <a href="/facts/Granulocyte/zsE3ldLb">granulocytes</a>, <a href="/facts/Lymphocyte/pS2pv2Ma">lymphocytes</a> and <a href="/facts/Monocyte/FW4NNMKM">monocytes</a>.
All white blood cells are produced and derived from <a href="/facts/Multipotent/81323LbR">multipotent</a> cells in the <a href="/facts/Bone_marrow/4dfudk0H">bone marrow</a> known as <a href="/facts/Hematopoietic_stem_cell/RQNE9IRu">hematopoietic stem cells</a>. Leukocytes are found throughout the body, including the <a href="/facts/Blood/03zEulkj">blood</a> and <a href="/facts/Lymphatic_system/yw5QLgMT">lymphatic system</a>. All white blood cells have <a href="/facts/Cell_nucleus/D7sFRa3c">nuclei</a>, which distinguishes them from the other <a href="/facts/Blood_cell/lf9GA0Dj">blood cells</a>, the anucleated <a href="/facts/Red_blood_cell/Kggpq8Jh">red blood cells</a> (RBCs) and <a href="/facts/Platelet/I0xrDVGa">platelets</a>. The different white blood cells are usually classified by <a href="/facts/Cell_division/n5MrunWj">cell</a> lineage (<a href="/facts/Myelocyte/VKRWVD78">myeloid cells</a> or <a href="/facts/Lymphocyte/pS2pv2Ma">lymphoid cells</a>). White blood cells are part of the body's immune system. They help the body fight <a href="/facts/Infection/182XrncP">infection</a> and other diseases. Types of white blood cells are granulocytes (neutrophils, eosinophils, and basophils), and agranulocytes (<a href="/facts/Monocyte/FW4NNMKM">monocytes</a>, and <a href="/facts/Lymphocyte/pS2pv2Ma">lymphocytes</a> (T cells and B cells)). Myeloid cells (<a href="/facts/Myelocytes/VKRWVD78">myelocytes</a>) include <a href="/facts/Neutrophil_granulocyte/KL6oTt8b">neutrophils</a>, <a href="/facts/Eosinophil_granulocyte/yhIKA8bE">eosinophils</a>, <a href="/facts/Mast_cells/szfXss5q">mast cells</a>, <a href="/facts/Basophil_granulocyte/FRN1ugHk">basophils</a>, and <a href="/facts/Monocyte/FW4NNMKM">monocytes</a>. Monocytes are further subdivided into <a href="/facts/Dendritic_cells/19KBuKFK">dendritic cells</a> and <a href="/facts/Macrophages/z7hkQu3o">macrophages</a>. Monocytes, macrophages, and neutrophils are <a href="/facts/Phagocytic/eBrv2XKV">phagocytic</a>. Lymphoid cells (<a href="/facts/Lymphocytes/pS2pv2Ma">lymphocytes</a>) include <a href="/facts/T_cells/5z6PQ9UN">T cells</a> (subdivided into <a href="/facts/Helper_T_cell/nhwAYkDj">helper T cells</a>, <a href="/facts/Memory_T_cell/xsavrTuS">memory T cells</a>, <a href="/facts/Cytotoxic_T_cell/e5eRg3XJ">cytotoxic T cells</a>), <a href="/facts/B_cells/6Y1tgwwp">B cells</a> (subdivided into <a href="/facts/Plasma_cells/1fY4bFHR">plasma cells</a> and <a href="/facts/Memory_B_cells/3Qaz8Pxd">memory B cells</a>), and <a href="/facts/Natural_killer_cells/A3THWxrJ">natural killer cells</a>. Historically, white blood cells were classified by their physical characteristics (<a href="/facts/Granulocytes/zsE3ldLb">granulocytes</a> and <a href="/facts/Agranulocytes/UNsRkKKK">agranulocytes</a>), but this classification system is less frequently used now. Produced in the <a href="/facts/Bone_marrow/4dfudk0H">bone marrow</a>, white blood cells defend the body against <a href="/facts/Infection/182XrncP">infections</a> and <a href="/facts/Disease/55eeQlGL">disease</a>. An excess of white blood cells is usually due to infection or inflammation. Less commonly, a high white blood cell count could indicate certain blood cancers or bone marrow disorders.
The number of leukocytes in the blood is often an indicator of <a href="/facts/Disease/55eeQlGL">disease</a>, and thus the white blood cell count is an important subset of the <a href="/facts/Complete_blood_count/NF9lNJL3">complete blood count</a>. The normal white cell count <a href="/facts/Reference_ranges_for_blood_tests/Fls5Gbtb">is usually</a> between 4 × 109/L and 1.1 × 1010/L. In the US, this is usually expressed as 4,000 to 11,000 white blood cells per microliter of blood. White blood cells make up approximately 1% of the total blood volume in a healthy adult, making them substantially less numerous than the <a href="/facts/Hematocrit/wg1UalUh">red blood cells at 40% to 45%</a>. However, this 1% of the blood makes a huge difference to health because <a href="/facts/Immunity_(medical)/vLPpzSNL">immunity</a> depends on it. An increase in the number of leukocytes over the <a href="/facts/Reference_ranges_for_blood_tests/Fls5Gbtb">upper limits</a> is called <a href="/facts/Leukocytosis/RNyMWBzl">leukocytosis</a>. It is normal when it is part of healthy immune responses, which happen frequently. It is occasionally abnormal when it is <a href="/facts/Neoplasm/K0ytzmPz">neoplastic</a> or <a href="/facts/Autoimmunity/5cASmcfI">autoimmune</a> in origin. A decrease below the lower limit is called <a href="/facts/Leukopenia/LB1Avvby">leukopenia</a>, which indicates a weakened immune system.

White blood cell open-in-new

White blood cell