White blood cells or leukocytes are cells which form a component of the blood. They are produced in the bone marrow and help to defend the body against infectious disease and foreign materials as part of the immune system. White blood cells are also found in large numbers in the lymphatic system, the spleen, and in other body tissues.

There are many different types of white blood cells. One primary technique to classify them is to look for the presence of granules, which produces the categories "granulocytes" and "agranulocytes". Granulocytes are a category of white blood cells, characterised by the fact that all types have differently staining granules in their cytoplasm on light microscopy. These granules are related to lysosomes found in some regular cells and primarily act in the digestion of engulfed invaders. There are three types of granulocytes: neutrophils, basophils, and eosinophils (named according to their staining properties). Agranulocytes are a category of white blood cells which are characterized by the absence of granules in their cytoplasm. There are two types of agranulocytes: lymphocytes and monocytes.

8-OHdG (8-hydroxydeoxyguanosine)

• a marker of DNA damage in human leukocytes. PMID: 10656286

ATPase (adenosine triphosphatase)

• a marker enzyme for the plasma membrane of human polymorphonuclear leukocytes. PMID: 14892

Beta2 Leukocyte Integrins (CD11/CD18)

• a family of transmembrane receptors whose expression is restricted to leukocytes. PMID: 9441798
• serve as signaling partners for other leukocyte receptors. PMID: 9142045
• CD11a/CD18 are apparent on early progenitors of all myeloid and erythroid cells. CD11b/CD18 and CD11c/CD18 are more restricted antigens normally expressed on monocytes, macrophages, PMN and natural killer cells. PMID: 7628754

Cathepsin G

• a serine, chymotrypsin-like protease released by activated polymorphonuclear leukocytes (PMN) that may act as a platelet agonist. PMID: 8400294

CD15 (leuM1)

• a leukocyte marker, known to be expressed on mature myeloid cells in the hematopoietic lineage, is expressed on a wide variety of tumor cells including myeloid leukemia, breast, colorectal, lung cancer cells. PMID: 14624053, PMID: 7488522, PMID: 1979722

CD18 (MHM23)

• reacts with all leukocytes. PMID: 8969052
• a leukocyte marker not expressed by mast cells. PMID: 1372025

CD43 (leukosialin, leu-22)

• a transmembrane sialoglycoprotein, is abundantly expressed on the surface of hematopoietic cells. PMID: 14676827

CD45

• leukocyte common antigen, is a pan-leukocyte marker. PMID: 11517296, PMID: 1532395

CD45RA/CD45RB/CD45RO

• restricted leukocyte common antigens. PMID: 1828514, PMID: 8310638, PMID: 1420566
• Characterization of a monoclonal antibody identifying a CD45RA antigen on feline leukocytes. PMID: 16040129

CD53 (Ox-44)

• a human cell-surface Ag expressed exclusively by nucleated cells of hemopoietic origin. PMID: 2258620
• leukocyte antigen contributes to the transduction of CD2-generated signals in T cells and natural killer (NK) cells and has been suggested to play a role in growth regulation. PMID: 8404042

CD68 (KPI, macrosialin)

• macrophage specific antigen in blood leukocytes infiltrating the cervical tissue. PMID: 11517296

CD95 (fas)

• expressed in hematopoietic tissues during the final stages of development of monocytes, granulocytes, NK cells and T cells, but to a much lesser extent on B cells. PMID: 12880639

CD166

• activated leukocyte cell adhesion molecule (ALCAM). PMID: 16204050
• a type I transmembrane cell adhesion molecule belonging to the Ig superfamily and a ligand for CD6 that is expressed on T lymphocytes. PMID: 12843199

Diiodotyrosine (DIT)

• a possible new marker of leukocyte activity. PMID: 2005222

EFCC

• revealed different leukocyte subpopulations and various staining patterns on tissues. PMID: 15784291

Fecal Lactoferrin

• a marker of fecal leukocytes. PMID: 1583125

Glucose-6-phosphatase (G-6-Pase)

• a cytochemical marker of endoplasmic reticulum in human leukocytes and platelets. PMID: 6319482

HLA (human leukocyte antigen)

• widely expressed cell surface molecules that present antigenic peptides to T-lymphocytes. PMID: 16314951

HLE (Human Leukocyte Elastase)

• Neutrophils contain human leukocyte elastase (HLE), which is released at sites of inflammation. PMID: 15245434

ICAM-1

• mediate early interaction and adhesion of neutrophils to coronary endothelial cells and myocytes after myocardial ischemia and reperfusion. PMID: 11123218
• plays a major role in deteriorating myocardial function during the reperfusion, possibly by leukocyte-mediated inflammatory process. PMID: 11093482
• a ligand for lymphocyte function-associated antigen (LFA)-1alpha and has been shown to be required for leukocyte migration into inflamed areas. PMID: 10836326
• plays an important role in microvascular leukocyte recruitment in both ALI and FIB in the BLM-injured lung. PMID: 10806175
• the main ligand responsible for slow leukocyte rolling mediated by Mac-1, but not LFA-1. PMID: 14634125

IL-8 (Interleukin-8)

• function as a PMN-directed leukocyte adhesion inhibitor and suggest that local secretion of IL-8 by activated endothelium may differentially modulate leukocyte-endothelial interactions at sites of acute inflammation. PMID: 1650387
• IL-8 released from monocytes and synovial cells may be an important contributor to leukocyte accumulation and inflammatory events in the joints of rheumatoid arthritis (RA). PMID: 1932367

L1

• an approximately 36-kd protein recently identified as a cytoplasmic and surface marker antigen of virtually all resting peripheral blood neutrophils and monocytes. PMID: 2438925

Lactoferrin

• a promoter of polymorphonuclear leukocyte adhesiveness. PMID: 7214024
• neutrophil-derived lactoferrin contributes to the inflammatory response by promoting further granulocyte accumulation and activation. PMID: 7515095

LAM-1 (Leukocyte Adhesion Molecule-1)

• a member of a new family of cell adhesion molecules and the human lymphocyte homing receptor. PMID: 1712791
• a major mediator of leukocyte attachment to activated human endothelium. PMID: 1717567,
• regulates the migration of human leukocytes by mediating the binding both of lymphocytes to high endothelial venules of peripheral lymph nodes and of neutrophils to endothelium at inflammatory sites. PMID: 1705015

LAP (Leukocyte alkaline phosphatase)

• represents a specific and restrictive marker for the terminal maturation of the neutrophilic granulocyte. PMID: 9031080

Lectins

• markers for eosinophilic leukocytes. PMID: 2437079

L-selectin

• mediates lymphocyte migration to peripheral lymph nodes and leukocyte rolling on vascular endothelium during inflammation. PMID: 14614858, PMID: 12165530
• plays a significant role in leukocyte rolling and adherence to venular endothelium in rat skeletal muscle ischemia reperfusion injury. PMID: 10522850

LSP1 (Leukocyte-specific protein-1)

• pan-leukocyte marker. PMID: 15339679
• an F-actin bundling cytoskeletal protein expressed in hematopoietic lineage and endothelial cells. PMID: 17003510
• important in leukocyte chemotaxis, expressed in leukocytes as well as in endothelium regulates neutrophil transendothelial migration. PMID: 15684321
• a cytoskeletal-associated protein of leukocytes that in vitro cross-links F-actin into extensively branched bundles of mixed polarity, plays important roles in the regulation of neutrophil morphology, motility, and superoxide production. PMID: 11261799
• a negative regulator of neutrophil chemotaxis and an F-actin binding protein expressed in lymphocytes, macrophages, and neutrophils in mice and humans. PMID: 10961883

Ly-9

• a new marker for the study of normal and malignant leukocytes. PMID: 11369645

M6 (leukocyte activation antigen)

• a novel human leukocyte activation-associated cell surface glycoprotein. PMID: 1634773

Mac-1

• mediates leukocyte activation and emigration from the bloodstream to the tissues. PMID: 16857989, PMID: 15464320

MPO (myeloperoxidase)

• a sensitive and quantitative marker of polymorphonuclear leukocytes (PMN) accumulation into an evolving myocardial infarction (MI). PMID: 2418303
• myeloperoxidase is a sensitive marker for monitoring in vivo activation of white blood cells. PMID: 1650868

VIP (Vasoactive Intestinal Polypeptide)

• a 28 amino acid peptide found in highest concentration in central and peripheral nervous tissue, is a biochemical marker for polymorphonuclear leukocytes. PMID: 6932456

Other Leukocyte Markers

• Colloidal gold as a marker for the light microscope detection of leukocyte cell surface antigens with monoclonal antibodies. PMID: 6752176
• Omega-exonuclease: an enzymatic marker for basophilic leukocytes and mast cells. PMID: 2547251
• Human leukocyte markers defined by monoclonal antibodies. I. Expression of X-hapten structure on cells of myeloid lineage. PMID: 2467863