CD4, a single chain transmembrane glycoprotein, is found on a T-cell subset (helper/inducer). It is also present on a variety of monocyte-derived cells, including Langerhans and other dendritic cells. The CD4 epitope is absent from immature thymocytes and is expressed during T-cell development. Precursor T-lymphoblastic lymphomas are therefore variable in their expression of CD4, but most mature T-cell lymphomas are positive, with the exception of aggressive NK-cell leukemia, extranodal NK-cell lymphoma, gamma delta T-cell lymphomas, and enteropathy-type T-cell lymphoma.
CD43 (leukosialin, sialophorin, or leukocyte sialoglycoprotein) is a cell surface glycoprotein that is expressed on all thymocytes, T-cells, and cells of myeloid lineage. CD43 antibody can be useful in the diagnosis of T-cell lymphoma and a subset of B-cell lymphoma. CD43 expression in lymphomas is highly correlated with CD5; thus, most T-cell malignancies and a group of small lymphocyte B-cell malignancies (CLL/SLL, mantle cell lymphoma, and prolymphocytic leukemia (PLL)) are often positive, whereas follicular lymphoma is rarely positive. CD43 is also positive in about 50% of cases of Burkitt lymphoma.
The CD44 family of glycoproteins exists in a number of variant isoforms, including hematopoietic variant (CD44s) and epithelial cells variant (CD44v). While many human tumors express CD44, a positive correlation between increased CD44 expression and tumor progression has been demonstrated in only some. The most practical application of CD44 immunostaining at present is the discrimination of urothelial transitional call carcinoma-in-situ from non-neoplastic changes in the urothelium.
CD45 (Leukocyte Common Antigen, LCA) is comprised of at least four isoforms (CD45RA, CD45RB, CD45RC and CD45RO) of membrane glycoproteins. CD45 is expressed on hematopoietic cells (human leukocytes, including lymphocytes, monocytes, and eosinophils), but is absent on normal and malignant non-hematopoietic tissues.
CD5, a transmembrane protein, is found on most thymocytes and immature peripheral T-cells. It stains normal B-cells of mantle zone of spleen and lymph nodes, B-cells in peritoneal and pleural cavities, and almost all T-cells. In a fetus, most B-cells in spleen and cord blood are CD5 positive. It stains B-cell chronic lymphocytic leukemia/ small lymphocytic leukemia (CLL/SLL), mantle cell lymphoma (MCL), hairy cell leukemia (HCL), most T-malignancies, and most thymic carcinomas. CD5 is usually negative in spindle cell thymoma.
CD56 recognizes two proteins of the neural cell adhesion molecule, the basic molecule expressed on most neuroectodermally-derived cell lines, tissues and neoplasms (e.g. retinoblastoma, medulloblastomas, astrocytomas, and neuroblastomas). It is also expressed on some mesodermally-derived tumors (rhabdomyosarcoma) and on natural killer cells. CD56 can be used as a marker for NK cell neoplasms. Some benign and malignant plasma cells are also positive. CD56 is often positive in neuroendocrine carcinomas.
CD57 is expressed on subpopulations of peripheral blood mononuclear cells, NK active cells and T-cells. Hematopoietic malignancies that are CD57+ include a minority of T-lymphoblastic leukemias, roughly three quarters of the indolent T-cell large granular lymphocytic leukemias, and a small portion of NK-cell lymphomas. It can be used to highlight small lymphoid cells in nodular lymphocytic predominant Hodgkin lymphoma.
CD61 (GPIIIa) is a glycoprotein found on megakaryocytes, platelets, and their precursors. CD61 antigen plays a role in platelet aggregation and also as a receptor for fibrinogen, fibronectin, von Willebrand factor, and vitronectin. This antibody is useful in detecting neoplastic platelet precursors, normal platelets, and most cases of megakaryocytic leukemias.
CD68 is an antibody directed against lysosomes. It is important for identifying macrophages in tissue sections. It stains macrophages in a wide variety of human tissues, including Kupffer cells and macrophages in the red pulp of the spleen, lamina propria of the gut, lung alveoli, and bone marrow. This antibody reacts with myeloid precursors and peripheral blood granulocytes. It shows strong granular cytoplasmic staining of chronic and acute myeloid leukemia and also reacts with true histiocytic neoplasia. It also stains granular cell tumors and some cases of melanoma, renal cell carcinoma, and pleomorphic sarcoma. Tumors of lymphoid origin are usually not stained.
CD7 is expressed on the majority of immature and mature T-lymphocytes and T-cell leukemia. It is also found on natural killer cells, and a small subpopulation of normal and malignant B-cells. CD7 antibody can be useful for detection of T-cell leukemias and myeloid leukemias. CD7 expression is often lost in mycosis fungoides.