cluster of differentiation

Cell membrane molecules that are used to classify leukocytes into subsets. CD molecules are classified by monoclonal antibodies. There are four general types: type I transmembrane proteins have their COOH-termini in the cytoplasm and their NH2-termini outside the cell; type II transmembrane proteins have their NH2-termini in the cytoplasm and their COOH-termini outside the cell; type III transmembrane proteins cross the plasma membrane more than once and hence may form transmembrane channels; and glycosylphosphatidylinositol-anchored proteins (type IV), which are tethered to the lipid bilayer via a glycosylphosphatidylinositol anchor.

- CD1a a type I transmembrane protein found on thymocytes, Langerhans cell, brain astrocytes, and dermal cells that is involved in nonclassical antigen presentation or is a receptor for an undefined ligand or hormone; expressed in patients with T-cell acute lymphoblastic leukemia, histiocytosis X, and thymomas.

- CD1b a type I transmembrane protein found on cortical thymocytes, dermal cells, and brain astrocytes that is involved in nonclassical antigen presentation or is a receptor for an undefined ligand or hormone; expressed in patients with T-cell acute lymphoblastic leukemia, T-cell lymphoma, and thymomas.

- CD1c a type I transmembrane protein found on cortical thymocytes, dermal cells, and brain astrocytes that is involved in nonclassical antigen presentation or is a receptor for an undefined ligand or hormone; expressed in patients with T-cell acute lymphoblastic leukemia, B-cell chronic lymphocytic leukemias, and B cells in severe combined immunodeficiency disease.

- CD2 a type I transmembrane protein found on thymocytes, T cells, and some natural killer cells that acts as a ligand for CD58 and CD59 and is involved in signal transduction and cell adhesion; expressed in T-cell acute lymphoblastic leukemia and T-cell lymphoma.

- CD2r a type I transmembrane protein found on T cells and some natural killer cells that is unrelated to binding sites for CD58 and CD59; expressed on activated T cells in autoimmune diseases.

- CD3 a type I transmembrane protein found on T cells that forms the signal transduction unit for the T cell; expressed in patients with T-cell lymphomas.

- CD4 a type I transmembrane protein found on helper/inducer T cells, monocytes, macrophages, and dendritic cells that is involved in T-cell recognition of antigens; expressed in mycosis fungoides, Sézary syndrome, and T-cell lymphomas.

- CD5 a type I transmembrane protein found on T cells, thymocytes, and some B cells that is a ligand for CD72 and is involved in cellular activation or adhesion; expressed in B-cell chronic lymphocytic leukemia and T-cell lymphoma.

- CD6 a type I transmembrane protein found on T cells, medullary thymocytes, some cortical thymocytes, a few B cells, and in brain. CD6 is phosphorylated on cellular activation and possibly plays a role in signal transduction; expressed in some B-cell chronic lymphocytic leukemias.

- CD7 a type I transmembrane protein found on thymocytes, some T cells, monocytes, natural killer cells, and hemopoietic stem cells; expressed in patients with mycosis fungoides, some patients with T-cell acute lymphoblastic lymphoma, and a few patients with acute nonlymphocytic lymphoma.

- CD8 a type I transmembrane protein found on suppressor (cytotoxic) T cells, some natural killer cells, and most thymocytes that is involved in T-cell antigen recognition; expressed in some T-cell lymphomas and large granular lymphocyte leukemias.

- CD9 a type III transmembrane protein found on platelets, megakaryocytes, monocytes, pre-B cells, eosinophils, basophils, and activated T cells; plays a role in signal transduction leading to platelet activation and aggregation; expressed in some T-cell acute lymphocytic leukemias and some acute nonlymphocytic leukemias.

- CD10 a type II transmembrane protein found on pre-B cells, germinal-center B cells, some neutrophils, kidney cells, T-cell precursors, and epithelial cells that acts as a zinc metalloprotease cleaving peptide bonds on the amino side of hydrophobic amino acid s; expressed in acute lymphocytic leukemia and follicular-center–cell lymphomas.

- CD11a a type I transmembrane protein found on lymphocytes, neutrophils, monocytes, and macrophages that facilitates cell adhesion and cell activation; expressed in lymphomas.

- CD11b a type I transmembrane protein found on monocytes, macrophages, granulocytes, some B cells, dendritic cells, and natural killer cells that facilitates cell adhesion, phagocytosis, and/or chemotaxis; expressed in some B-cell chronic lymphocytic leukemias, most acute nonlymphocytic leukemias, and some hairy cell leukemias.

- CD11c a type I transmembrane protein found on monocytes, macrophages, neutrophils, and some B cells that induces cellular activation and helps trigger neutrophil respiratory burst; expressed in hairy cell leukemias, acute nonlymphocytic leukemias, and some B-cell chronic lymphocytic leukemias.

- CDw12 a membrane protein found on monocytes, neutrophils, and platelets; the function of this moiety is unknown.

- CD13 a type II transmembrane protein found on myeloid cells that acts as a zinc-binding metalloprotease catalyzing removal of NH2-terminal amino acid s from peptides; expressed in some types of acute nonlymphocytic leukemia.

- CD14 a transmembrane protein found on monocytes, macrophages, neutrophils, some B cells, and dendritic cells that is involved in signal transduction leading to oxidative burst and/or synthesis of tumor necrosis factor-α; expressed in some patients with acute nonlymphocytic leukemia and in B-cell chronic lymphocytic leukemia.

- CD15 a phosphatidylinositol-anchored transmembrane protein found on neutrophils and which may be involved in phagocytosis; expressed in patients with Hodgkin disease, some B-cell chronic lymphocytic leukemias, acute lymphoblastic leukemias, and most acute nonlymphocytic leukemias.

- CD15s a transmembrane protein found on neutrophils, monocytes, myeloid cells, and some T cells that serves as the major ligand for CD62E; expressed on squamous cell carcinomas.

- CD16 a type I transmembrane protein found on natural killer cells and macrophages that is involved in directing NK cell activation.

- CD16b a glycosylphosphatidylinositol-anchored protein present on neutrophils; deficient in patients with paroxysmal nocturnal hemoglobinemia and expressed in large granular lymphocytic leukemias and natural killer cell leukemias.

- CDw17 a type I transmembrane protein found on monocytes, neutrophils, and platelets that may play a role in granule content packaging or exocytosis.

- CD18 a type I transmembrane protein found on lymphocytes, neutrophils, monocytes, macrophages, some B cells, dendritic cells, and natural killer cells that appears active in signal transduction; expressed in some patients with B-cell chronic lymphocytic leukemia, most acute nonlymphocytic leukemia, and some hairy cell leukemia.

- CD19 a type I transmembrane protein found on all B cells and B-cell precursors and some follicular dendritic cells that acts as an accessory molecule for B cell signal transduction; expressed in all B-cell neoplasms.

- CD20 a type III transmembrane protein found on B cells that forms a calcium channel in the cell wall allowing for the influx of calcium required for cell activation; expressed in B-cell lymphomas, hairy cell leukemia, and B-cell chronic lymphocytic leukemia.

- CD21 a type I transmembrane protein found on B cells, follicular dendritic cells, pharyngeal and cervical epithelial cells, some thymocytes, and some T cells that plays a role in signal transduction; expressed in hairy cell leukemia, B-cell lymphoma, and some T-cell acute lymphocytic leukemias.

- CD22 a type I transmembrane protein found in the cytoplasm of pre-B cells and on the surface of mature B cells that facilitates signal transduction; expressed in patients with hairy cell leukemias and in some with B-cell lymphomas.

- CD22α a type I transmembrane protein found on mature B cells that facilitates adhesion of B cells to monocytes and red blood cells.

- CD22β a type I transmembrane protein found on mature B cells that facilitates adhesion of B cells to CD4-positive T cells.

- CD23 a type II transmembrane protein found on mature B cells, monocytes, activated macrophages, eosinophils, platelets, and dendritic cells that enhances capture and processing of antigen complexed with IgE.

- CD24 a glycosylphosphatidylinositol-anchored protein present on B cells, pre-B cells, neutrophils, and a few thymocytes that may play a role in inducing B-cell proliferation and differentiation; expressed in patients with B-cell lymphomas and some with B-cell chronic lymphocytic leukemias.

- CD25 a type I transmembrane protein present on activated T cells, activated B cells, some thymocytes, myeloid precursors, and oligodendrocytes that associates with CD122 to form a heterodimer that can act as a high-affinity receptor for IL-2; expressed in most B-cell neoplasms, some acute nonlymphocytic leukemias, and neuroblastomas.

- CD26 a type II transmembrane protein present on mature T cells, some B cells, apical membranes of epithelial and endothelial cells, kidney, intestinal brush borders, and liver bile canaliculi that combines with collagen and associates with adenosine deaminase.

- CD27 a type I transmembrane protein present on mature T cells, medullary thymocytes, and some B cells that is a ligand for CD70 and serves as a member of the nerve growth factor family; expressed in chronic lymphocytic leukemia.

- CD28 a type I transmembrane protein present on most CD4 T cells, many CD8 T cells, and most plasma cells that enhances the transcription and stability of IL-2 messenger RNA.

- CD29 a type I transmembrane protein present on some CD4 helper T cells, platelets, and dendritic cells that is involved in cell-cell or cell-matrix adhesion.

- CD30 a type I transmembrane protein present on activated T and B cells that may play a role in cell activation and/or differentiation; expressed in Hodgkin disease, some T-cell lymphomas, and anaplastic large cell lymphomas.

- CD30l a type III transmembrane protein present on activated T cells and monocytes that can induce differential responses in CD30-expressing cells ranging from growth to cell death.

- CD31 a type I transmembrane protein present on myeloid cells, platelets, endothelial cells, natural killer cells, monocytes, and subsets of CD4-positive T cells that acts as a cosignal transducer for macrophages, inducing respiratory burst; plays a key role in the transmigration of leukocytes through intercellular junctions of vascular endothelium and mediates calcium-dependent heterophilic aggregation; expressed in neoplastic endothelial cells.

- CD32 a type I transmembrane protein present on monocytes, B cells, neutrophils, placental trophoblasts, and endothelium; acts as a signal transducer for IgG-mediated phagocytosis and neutrophil and monocyte oxidative burst; transduces an inhibitory signal on B cells and may play a role in placental IgG transport.

- CD33 a type I transmembrane protein present on myeloid cells and myeloid precursors; expressed in many acute nonlymphoblastic leukemias and some B-cell chronic lymphocytic leukemias.

- CD34 a type I transmembrane protein present on myeloid cells and myeloid precursors that plays a role in signal transduction; expressed in some acute nonlymphocytic leukemias and some acute lymphocytic leukemias.

- CD35 a type I transmembrane protein present on monocytes, granulocytes, dendritic cells, red blood cells, some T cells, and glomerular podocytes that facilitates phagocytosis and/or binding of immune complexes; expressed in Wilms tumor.

- CD36 a transmembrane protein present on monocytes, platelets, megakaryocytes, umbilical vein, small-vessel endothelium, reticulocytes, and mammary epithelium that may be involved in signal transduction; expressed in myeloproliferative disorders.

- CD37 a type III transmembrane protein present on mature B cells, some T cells, and monocytes that may play a role in ion transport; expressed on B-cell lymphomas, B-cell chronic lymphocytic leukemia, and hairy cell leukemia.

- CD38 a transmembrane protein present on macrophages, dendritic cells, and activated cells of the natural killer, B- and T-cell lines that can facilitate B-cell adhesion.

- CD39 a transmembrane protein present on macrophages, dendritic cells, and activated lymphoid cells that facilitates B-cell adhesion.

- CD40 a type I transmembrane protein present on mature B cells, monocytes, dendritic cells, and epithelial cells involved in signal transduction leading to cell activation, proliferation, adhesion, and/or differentiation; expressed in B-cell chronic lymphocytic leukemias, lymphomas, and some carcinomas.

- CD40l a type II transmembrane protein present on activated CD4-positive T cells, a few activated CD8-activated T cells, and blood basophils; a ligand for CD40 that induces activation, proliferation, and/or differentiation of CD40-expressing cells.

- CD41 a type I transmembrane protein present on platelets and megakaryocytes that serves as a receptor for fibrinogen, fibronectin, vitronectin, von Willebrand factor, and other factors and facilitates platelet adhesion and aggregation.

- CD42 a type I transmembrane protein present on platelets and megakaryocytes that mediates platelet binding to damaged blood vessel s.

- CD43 a type I transmembrane protein present on thymocytes, T cells, granulocytes, monocytes, natural killer cells, platelets, brain, activated B cells, plasma cells, and hemopoietic stem cells that serves as a ligand for CD54 and facilitates cell-cell adhesion; expressed on some myelomas and lymphomas.

- CD44 a type I transmembrane protein present on T cells, pre-B cells, monocytes, neutrophils, CNS white matter, fibroblasts, skeletal muscle, and medullary thymocytes; facilitates lymphocyte binding to endothelial venules and assists in adhesion.

- CD45 a type I transmembrane protein present on all hemopoietic cells except erythrocytes that assists in cell activation; expressed in lymphomas, B-cell chronic lymphocytic leukemia, hairy cell leukemia, and acute nonlymphocytic leukemia.

- CD46 a type I transmembrane protein present on thymocytes, T cells, B cells, natural killer cells, monocytes, neutrophils, platelets, endothelial cells, epithelial cells, fibroblasts, placenta, and sperm that protects against complement-mediated damage.

- CD47 a transmembrane protein without tissue specificity that is involved in membrane cation flux.

- CD48 a glycosylphosphatidylinositol-anchored membrane protein present on T cells, B cells, thymocytes, eosinophils, neutrophils, bronchial epithelium, and salivary gland that may play a role in signal transduction on T cells; absent or defective in patients with paroxysmal nocturnal hemoglobinuria.

- CD49a a type I transmembrane protein present on activated T and B cells, monocytes, neurovascular endothelium, and smooth muscle that forms a receptor for collagen and laminin; expressed on melanomas.

- CD49b a type I transmembrane protein present on platelets, T cells, B cells, fibroblasts, and endothelial cells involved in platelet adhesion of collagen; may be expressed in melanomas.

- CD49c a type I transmembrane protein present on B cells, kidney glomerulus, thyroid, and some basement membranes that may play a role in cell-cell adhesion; expressed in most cultured cell lines.

- CD49d a type I transmembrane protein present on B and T cells, natural killer cells, eosinophils, monocytes, erythroblasts, thymocytes, and myoblasts that facilitates cell-cell adhesion and leukocyte migration and aids in lymphocyte activation; expressed in melanomas.

- CD49e a type I transmembrane protein present on monocytes, neutrophils, leukocytes, fibroblasts, platelets, and myoblasts that helps form a receptor for fibronectin and activates the sodium-hydrogen antiporter; may serve an accessory role to T-cell activation.

- CD49f a type I transmembrane protein present on platelets, macrophages, monocytes, thymocytes, T cells, and adherent cell lines that forms a receptor for invasion and laminin; expressed in some acute lymphocytic leukemias.

- CD50 a type I transmembrane protein present on thymocytes, B cells, monocytes, and neutrophils; involved in intracellular adhesion.

- CD51 a type I transmembrane protein present on endothelial cells, monocytes, macrophages, platelets, some B cells, osteoclasts, and uterine cells; plays a role in platelet aggregation and/or endothelial cell adhesion and in monocyte migration.

- CD52 a glycosylphosphatidylinositol-anchored membrane protein present on thymocytes, T cells, B cells, some granulocytes, seminal vesicles, epididymis, and spermatozoa; plays a role in signal transduction.

- CD53 a type III transmembrane protein present on leukocytes, platelets, osteoblasts, and osteoclasts; contributes to the transduction of CD2-generated signals in T cells and natural killer cells; facilitates cytoplasmic calcium flux in B cells, monocytes, and granulocytes; and plays a role in activation of the monocyte oxidative burst; expressed in hemopoietic neoplasms and myelomas.

- CD54 a type I transmembrane protein present on leukocytes and endothelial cells and inducible on lymphocytes, dendritic cells, keratinocytes, chondrocytes, fibroblasts, and epithelial cells; acts as a ligand for CD11 and CD18 and aids in intercellular adhesion.

- CD55 a glycosylphosphatidylinositol-anchored membrane protein present on all hemopoietic cells and spermatozoa that neutralizes complement activation; absent or defective in paroxysmal nocturnal hemoglobinuria.

- CD57 a membrane protein present on natural killer cells, some T cells, a few B cells, and monocytes of unknown function; expressed in large granular lymphocyte leukemias.

- CD58 a membrane protein present on many hemopoietic cells and fibroblasts that acts as a ligand for CD2 and may be involved in T-cell function.

- CD59 a glycosylphosphatidylinositol-anchored membrane protein present on many hemopoietic cells, vascular endothelium, epithelial cells, and placenta that inhibits membrane complement attack and may be involved in T-cell signal transduction; absent or defective in paroxysmal nocturnal hemoglobinuria.

- CDw60 a membrane protein present on T-cell subsets, some monocytes, and platelets that may play a role in signal transduction leading to cell activation; present on cutaneous T-cell lymphomas.

- CD61 a membrane protein present on platelets, megakaryocytes, endothelial cells, osteoclasts, and uterine cells that facilitates platelet aggregation and adhesion.

- CD62e a type I transmembrane protein present on endothelium that facilitates adhesion of neutrophils, monocytes, and some T cells to vascular endothelium; enhanced expression occurs at sites of chronic inflammation.

- CD62l a type I transmembrane protein present on B cells, T cells, neutrophils, thymocytes, monocytes, eosinophils, erythroid and myeloid progenitor cells, and natural killer cells that functions as a peripheral lymph node homing receptor and facilitates binding to endothelium at inflammatory sites; found on many malignant leukocytes.

- CD62p a type I transmembrane protein present on activated platelets, endothelial cells, and megakaryocytes that facilitates adhesion of monocytes and neutrophils to activated platelets and to endothelial cells.

- CD63 a type III transmembrane protein present on activated platelets, monocytes, macrophages, and in secretory granules of vascular endothelial cells and platelet-dense granules; facilitates adhesion to activated endothelium.

- CD64 a type I transmembrane protein present on monocytes, megakaryocytes, and activated neutrophils that acts as a high-affinity receptor for IgG; present in some cases of acute nonlymphocytic leukemia.

- CDw65 a membrane protein present on myeloid cells and some monocytic cells that is involved in signal transduction leading to formation of the respiratory burst; present in some acute nonlymphocyte leukemias.

- CD66a a type I transmembrane protein, present on neutrophils, histiocytes, some myeloid progenitor cells, and the brush border of colonic epithelial cells, that facilitates adhesion and neutrophilic activation; expressed in chronic myelocytic leukemia and some cases of acute lymphocytic leukemia.

- CD66b a glycosylphosphatidylinositol-anchored membrane protein present on neutrophils that induces aggregation and activation; expressed in chronic myelocytic leukemia.

- CD66c a glycosylphosphatidylinositol-anchored membrane protein present on neutrophils that induces aggregation and activation; expressed in chronic myelocytic leukemia.

- CD66d a type I transmembrane protein present on neutrophils that facilitates adhesion and neutrophil activation; expressed in chronic myelocytic leukemia.

- CD66e a glycosylphosphatidylinositol-anchored membrane protein present in tissues derived from all three germ layers during embryogenesis and adult colon epithelial cells that facilitates calcium-independent adhesion during embryogenesis; expressed in most colon carcinomas and other carcinomas.

- CD68 a type I transmembrane protein present on monocytes, macrophages, osteoclasts, mast cells, cytoplasmic granules, activated platelets, and large lymphocytes; expressed in neuroma Schwann cells, in nerves undergoing wallerian degeneration, in myeloid cell tumors, and in anaplastic lymphomas and epithelial tumors.

- CD69 a type II transmembrane protein present on platelets, CD4-positive or CD8-positive thymocytes, activated lymphocytes, and activated T or natural killer cells that functions as a signal transducer, enhancing cell activation and/or platelet aggregation.

- CD70 a type II transmembrane protein present on activated B cells and some activated T cells that enhances activation of T cells; expressed in Reed-Sternberg cells, some lymphomas, and monocyte lineage–derived tumors.

- CD71 a type II transmembrane protein present on activated or proliferating cells that facilitates cellular iron uptake; expressed in many acute leukemias and some lymphomas.

- CD72 a type II transmembrane protein present on all B cells and macrophages that plays a role in signal transduction or adhesion; expressed in B-cell acute lymphoblastic leukemia, B-cell lymphomas, and B-cell chronic lymphocytic leukemia.

- CD73 a glycosylphosphatidylinositol-anchored membrane protein present on some B cells, some T cells, thymocytes, some epithelial and endothelial cells, and dendritic cells; expressed on most B-cell acute lymphoblastic leukemias, breast carcinomas, and large granular leukocyte leukemias.

- CD74 a type II transmembrane protein present on B cells, monocytes, dendritic cells, and activated T cells that prevents binding of endogenous peptides; expressed in B-cell chronic lymphocytic leukemia, hairy cell leukemia, and large granular leukocyte lymphomas.

- CDw75 a type II transmembrane protein present on mature B cells and some T cells that may facilitate B-cell adhesion; expressed in B-cell lymphomas of follicular cell origin.

- CDw76 a membrane protein present on mature B cells, some T cells, melanocytes, endothelial cells, hepatocytes, and kidney tubular cells; expressed in mature B-cell lymphomas and B-cell chronic lymphocytic leukemias.

- CD77 a membrane protein present on germinal center B cells, follicular dendritic cells, endothelium, and some epithelial cells which may act as a receptor for toxins of Escherichia coli or Shigella dysenteriae; expressed in Burkitt lymphomas and B-cell lymphomas of follicular center cell origin.

- CDw78 a membrane protein present on B-cells and tissue macrophages that may be involved in signal transduction; expressed in some acute lymphoblastic leukemias, B-cell lymphomas, and some acute nonlymphocytic leukemias.

- CD79a a type I transmembrane protein present on B cells that mediates signal transduction; expressed in mature B-cell neoplasms.

- CD79b a type I transmembrane protein on B cells that mediates signal transduction; expressed in B-cell tumors and B-cell acute leukoblastic leukemias.

- CD80 a type I transmembrane protein on activated B cells, activated monocytes, activated follicular dendritic cells, and some activated T cells that provide a costimulatory signal to T cells during antigen presentation; expressed in B lymphoblastoid cells.

- CD81 a type III transmembrane protein present on many cell types, including lymphocytes, that facilitates signal transduction; expressed on lymphomas, leukemias, melanomas, and neuroblastomas.

- CD82 a type III transmembrane protein present on epithelial cells, endothelium, and activated lymphocytes that may play a role in calcium flux.

- CD83 a type I transmembrane protein, present on dendritic cells, Langerhans cells, B cells, and interdigitating reticular cells, that may play a role in antigen presentation or the cellular interactions that follow lymphocyte activation.

- CDw84 a membrane protein present on monocytes, early B cells, platelets, germinal-center B cells, mantle-zone B cells, and circulating lymphocytes.

- CD85 a membrane protein present on plasma cells, B cells, and monocytes.

- CD86 a membrane protein present on some germinal-center B cells, mitogen-activated B cells, and monocytes that serves as a B-cell activator; expressed in anaplastic large cell lymphomas, on Reed-Sternberg cells, and on Epstein Barr virus–transformed B cells.

- CD87 a glycosylphosphatidylinositol-anchored membrane protein present on activated T cells, monocytes, and activated neutrophils that plays a role in cell-surface plasminogen activation; expressed on macrophages at sites of inflammation.

- CD88 a type III transmembrane protein present on neutrophils, macrophages, eosinophils, mast cells, and smooth muscle cells that helps trigger chemotaxis and aids in cellular activation, respiratory burst, and degranulation; expressed in monocytoid tumors.

- CD89 a type I transmembrane protein present on neutrophils, monocytes, macrophages, and some T and B cells that assists in triggering granulocyte respiratory burst; expressed in monocytoid tumors.

- CDw90 a glycosylphosphatidylinositol-anchored membrane protein of unknown function present on prothymocytes and in brain and other nonlymphoid tissues.

- CD91 a membrane protein on monocytes and macrophages that may facilitate endocytosis.

- CDw92 a membrane protein present on neutrophils, platelets, and monocytes; of unknown function.

- CD93 a membrane protein present on neutrophils, monocytes, and endothelial cells; of unknown function.

- CD94 a membrane protein expressed on natural killer cells and a few T cells that stimulates natural killer cell cytolysis and release of tumor necrosis factor.

- CD95 a type I transmembrane protein present on T cells and myeloid cells that may induce apoptosis.

- CD96 a type I transmembrane protein present on T cells, natural killer cells, and activated B cells that is expressed primarily upon cellular activation, suggesting ligand-binding activity.

- CD97 a membrane protein of unknown function present on monocytes and mature granulocytes.

- CD98 a type II transmembrane protein present on monocytes, cardiac muscle cells, endothelial cells, T cells, B cells, and natural killer cells; probably involved in regulating calcium fluxes; increased on T cells in some autoimmune disease or in chronic hepatitis.

- CD99 a type I transmembrane protein present on thymocytes, lymphocytes, and myeloid cells involved in rosette formations with sheep erythrocytes.

- CD99r a type I transmembrane protein similar to CD99 but present on myeloid cells.

- CD100 a membrane protein present on hemopoietic cells that can induce proliferative responses.

- CDw101 a membrane protein of unknown function present on neutrophils, monocytes, and some T cells.

- CD102 a type I transmembrane protein present on endothelial cells, platelets, monocytes, dendritic cells, subsets of lymphocytes, and in splenic sinusoids that may facilitate recirculation of memory T cells.

- CD103 a type I transmembrane protein present on intestinal intraepithelial lymphocytes, some circulating leukocytes, and some T cells that facilitates adhesion to epithelia; expressed in hairy cell leukemia and some B-cell chronic lymphocytic leukemias.

- CD104 a type I transmembrane protein present on epithelia and thymocytes that facilitates adhesion of cells to the extracellular matrix; expressed in squamous cell carcinoma.

- CD105 a type II transmembrane protein present on endothelium, proerythryoblasts, activated monocytes and macrophages, and follicular dendritic cells that may play a role in adhesion; expressed in leukemic cells of B-lymphoid and myeloid origin.

- CD106 a type I transmembrane protein present on activated endothelial cells, macrophages, dendritic cells, marrow stroma, myoblasts, and myotubules that facilitates recruitment of leukocytes to sites of inflammation.

- CD107a a type I transmembrane protein present on activated platelets; increased expression noted on transformation of cells with metastatic potential and on embryonic cells.

- CD107b a type I transmembrane protein present on activated platelets; increased expression noted on transformation of cells with metastatic potential and on embryonic cells.

- CDw108 a glycosylphosphatidylinositol-anchored protein of unknown function present on activated T cells.

- CDw109 a glycosylphosphatidylinositol-anchored membrane protein of unknown function present on activated T cells, activated platelets, and endothelial cells.

- CD115 a type I transmembrane protein present on placenta, macrophages, monocytes, and monocyte-precursors that is involved in proliferation and differentiation of monocytes and their progenitors; expressed in choriocarcinomas.

- CDw116 a type I transmembrane protein present on monocytes, granulocytes, endothelial cells, dendritic cells, and fibroblasts that stimulates cell proliferation and differentiation; expressed in osteogenic sarcoma and breast and lung carcinomas.

- CD117 a type I transmembrane protein present on hemopoietic progenitors, mast cells, melanocytes, spermatogonia, oocytes, and some natural killer cells that assists in signal transduction to transfected cell lines; expressed in colon carcinomas.

- CD120a a type I transmembrane protein present on many cell types that has a high affinity for tumor necrosis factors.

- CD120b a type I transmembrane protein present on many cell types that has a high affinity for tumor necrosis factors.

- CDw121a a type I transmembrane protein present on T cells, thymocytes, chondrocytes, synovial cells, endothelial cells, fibroblasts, keratinocytes, and hepatocytes that aids in stimulation of cellular proliferation and/or activation.

- CDw121b a type I transmembrane protein present on B cells, monocytes, and macrophages that is involved in interaction with interleukins.

- CDw122 a type I transmembrane protein present on activated T cells, B cells, monocytes, and natural killer cells that may complex with CD25.

- CD123 a type I transmembrane protein present on pluripotent stem cells and committed hemopoietic progenitor cells that is involved in cell proliferation and/or differentiation.

- CDw124 a type I transmembrane protein present on mature B cells, T cells, epithelium, hemopoietic precursors, and fibroblasts that induces cell proliferation and/or activation; expressed in lymphomas and pancreatic, hepatic, and bladder tumors.

- CD125 a type I transmembrane protein present on eosinophils and basophils that stimulates cellular proliferation and/or differentiation.

- CD126 a type I transmembrane protein present on plasma cells, leukocytes, epithelial cells, fibroblasts, neural cells, and hepatocytes that stimulates cell growth and/or differentiation; possible growth factor for myelomas.

- CDw127 a type I transmembrane protein present on B-cell precursors, thymocytes, mature T cells, and monocytes that induces cell growth and/or differentiation.

- CDw128 a type III transmembrane protein present on neutrophils, basophils, monocytes, keratinocytes, and some T cells that induces chemotaxis and/or cell activation; expressed on melanoma cells.

- CD129 a type I transmembrane protein present on some T cells, myeloid and erythroid precursors, and mast cells that induces cell growth and/or differentiation; expressed in Hodgkin disease, large cell lymphomas, and megakaryoblastic leukemia.

- CDw130 a type I transmembrane protein present on most leukocytes, epithelial cells, fibroblasts, hepatocytes, and neural cells; interacts with leukemia inhibitor factors, interleukins, and other cell-proliferative factors.