Natural killer (NK) cells are a form of cytotoxic lymphocyte which constitute a major component of the innate immune system. NK cells play a major role in the host-rejection of both tumours and virally infected cells. They were named "natural killer" because of the initial notion that they do not require activation in order to kill cells which are "missing self" recognition ("missing-self" recognition is a term used to describe cells with low levels of MHC (major histocompatibility complex) class I cell surface marker molecules - a situation which could arise due to viral infection, or in tumors under strong selection pressure of killer T cells).

2B4 (CD244)

• a member of the CD2 subset of the immunoglobulin superfamily molecules expressed on natural killer (NK) cells and other leukocytes. PMID: 11513145

BAT

• can distinguish NK cells from other known subsets of T and B cells. PMID: 317706

CD2

• CD2 family members regulate natural killer (NK) cell lytic activity and inflammatory cytokine production when engaged by ligands on tumor cells. PMID: 16323413
• natural killer cell-surface protein. PMID: 15802510
• the NK cell triggering receptor, is a 50-55-kDa cell surface molecule that is also expressed on T cells. PMID: 1673433

CD3

• a common NK and T cell progenitor. PMID: 10738973

CD7

• one of the earliest T-lymphocyte Ag expressed during ontogeny, is also expressed on human NK cells. CD7-mediated signals appear to augment function of adhesion molecules on NK cells, which may be involved in NK cell activation by providing both anchorage and costimulatory triggering. PMID: 7506726

CD16 (Leu 11b)

• CD16 lymphocytes are potentially more cytotoxic than CD57 and CD8 cells. PMID: 1379859
• an immunoglobulin Fc receptor that allows NK cells to mediate antibody-dependent killing (ADCC), is a surface receptor of natural killer (NK) cells. PMID: 1673433

CD33

• A new subset of natural killer (NK) cells was identified in human umbilical cord blood. This subset of CD56+/CD3- NK cells co-expressed the CD33 antigen, which is present on early hematopoietic progenitors confined to the myeloid lineage. PMID: 7505004

CD45

• a pivotal enzyme in eliciting a precise subset of NK cell responses. PMID: 15867094
• CD45RA and CD45RO are genuine markers for naive and primed lymphocytes that represent distinct differentiation lineages. PMID: 1832950

CD56

• natural killer cell marker. PMID: 10504545, PMID: 9192774
• the natural killer cell antigen. PMID: 1695113
• a sensitive marker for Merkel cell carcinoma (MCC) as well as for NK-cell lymphoma, but is not specific. PMID: 16115052
• multiple isoforms of CD56 are differentially expressed on NK lines and play critical roles in the recognition/interaction of these cells with their specific allogeneic targets. PMID: 1709676
• The CD56 differentiation antigen, recognized by anti-Leu-19 and NKH-1 mAbs, is a 200-220-kD glycoprotein that is expressed predominantly on human NK cells and a minor subset of T lymphocytes mediating MHC-unrestricted cytotoxicity. PMID: 2478655

CD57/HNK1

• natural killer (NK) cell marker. PMID: 9378492
• known to react with some human leukocytes including all natural killer (NK) cells in peripheral blood. PMID: 6137899

CD69

• NK cell activation marker. PMID: 12688589
• a member of the natural killer cell gene complex family of signal transducing receptors. PMID: 7964477
• the earliest activation marker on the surface of cytokine- or mitogen-activated lymphocytes. PMID: 9188933
• a differentiation antigen expressed shortly after activation on T lymphocytes and other cells of haematopoietic origin, including natural killer (NK) cells, plays a crucial role in NK-cell function contributing to sustain NK-cell activation, as it has been previously demonstrated in T cells. PMID: 10447727
• CD69 is induced on NK cells not only by IL-2 and IFN-alpha but also by activation of the CD16 pathway, the interaction with NK target cells and the direct activation of PKC by phorbol 12-myristate 13-acetate (PMA), indicating that CD69 induction is associated to different NK activation pathways. PMID: 8477800
• a disulfide-linked homo-dimer expressed on the surface of activated T cells, B cells, natural killer cells, neutrophils and platelets, is a type II membrane glycoprotein related to a family of natural killer cell activation antigens. PMID: 8100776

CD107a

• a functional marker for the identification of natural killer cell activity. PMID: 15604012

CD161

• NK cell activation marker. PMID: 12688589

CD335/NKp46

• bovine NK cells. PMID: 19339058
• classically associated with CD3(-) natural killer (NK) cells. PMID: 18329100
• an Ig-like superfamily cell surface receptor involved in human NK cell activation. PMID: 17360655
• a major killer receptor expressed by NK cells. PMID: 21489674

CS1

• a novel member of the CD2 subset that contains two of the unique tyrosine motifs present in 2B4 and SLAM. Signaling through 2B4, CS1 and other members of the CD2 subset may play a major role in the regulation of NK cells and other leukocyte functions. PMID: 11513145

DPIV (dipeptidyl peptidase IV)

• a surface marker of human natural killer cells. PMID: 1980623

GM-1

• asialo GM1 display may be characteristic of NK cell populations and aid in the isolation of this population of cytotoxic cells. PMID: 6985637

H25 and H366

• natural killer surface markers. PMID: 2511721

HNK-1 (Leu 7)

• a monoclonal IgM antibody which recognizes a carbohydrate epitope on NK cells and a wide range of tumor cell types. PMID: 2456146

HP (Helix pomatia) Receptors

• represent the first simple and reliable marker detected on NK cells and might be useful for purification of this cell type. PMID: 309820

LAT (linker for activation of T cells)

• an integral membrane protein of 36-38 kd that plays an important role in T cell activation, is a novel immunohistochemical marker for T cells, NK cells, mast cells, and megakaryocytes. PMID: 10233842

Ly24 (Pgp-1)

• Murine natural killer cells express the Ly24 (Pgp-1) marker on their surface. PMID: 2404614

NKG2A and NKp80

• specific natural killer cell markers in rhesus and pigtailed monkeys. PMID: 15899917

NKH1 (N901)

• a natural-killer (NK) cell marker. PMID: 3315980
• a monoclonal antibody raised against interleukin 2-dependent human NK cell lines also recognizes all human neuroblastoma cell lines examined. PMID: 2456146

Protocadherin 15 (PCDH15)

• a new secreted isoform and a potential marker for NK/T cell lymphomas. PMID: 16369489

sialyl SSEA-1

• a carbohydrate marker of human natural killer cells and immature lymphoid cells. Expression of the sialyl SSEA-1 antigen is strictly limited to a distinct population of NK cells among the mature lymphocytes in normal PB, but the antigen is present in a wide range of immature lymphoblasts of T- and B-cell lineages as well as the NK-cell lineage. The sialyl SSEA-1 antigen disappears from the surface of immature lymphocytes of T- and B-cell lineages during the course of maturation. PMID: 2568858

Other Natural Killer (NK) Cell Markers

• Studies on the relationship of human natural killer and lymphokine-activated killer cells with lysosomal staining and analysis of surface marker phenotypes. PMID: 2456860
• Fluorescent europium chelates as target cell markers in the assessment of natural killer cell cytotoxicity. PMID: 8450237
• Studies on murine natural killer (NK) cells. V. Genetic analysis of NK cell markers. PMID: 2036678