CD 3

Accurate (CLBT3, T3, UCHT1), Ancell, Becton Dickinson (Leu 4), Biodesign, Biogenex (CD 3, 12F6), Bioprobe, Biosource (BB11), Boehringer Mannheim (4B5), Coulter (T3, CD 3), Cymbus Bioscience, Dako (T3-4B5, UCHT1), Exalpha (M2AB), Gen Trak, Immunotech (SPV-T3b), Novocastra (UCHT1) Ortho (OKT3), Pharmingen (HIT3A), Sanbio (MEM57), Serotec, Zymed (SPV-T36) and polyclonal CD 3 antisera from Dako, Serotec and Bioprobe/Tha.

The monoclonal antibodies are immunoreactive only in fresh-frozen section and cell preparations, whereas polyclonal antisera will react in fixed paraffin-embedded tissue, but only following HIER or prolonged enzyme digestion.

The CD 3 antigen consists of at least four structurally distinct membrane glycoproteins of molecular weight 20-28 kD. This complex, comprising extracellular, transmembrane and intracellular domains, is non-covalently associated with the polymorphic TCRa/b or, alternatively, the TCRg/d heterodimer. Stimulation of the CD 3 complex results in T-cell proliferation, release of cytokines and display of non-specific cytotoxicity, properties requiring the participation of accessory cells. It is believed that the CD 3 complex is responsible for mediating signal transduction to the internal environment upon antigenic recognition by the TCR, although the actual mechanisms of T-cell activation following antigen binding to the TCR are not known (Campana et al, 1987).
CD 3 is present in the cytoplasm prior to its detection on the cell surface of thymocytes and more than 95% of thymocytes bear surface and/or cytoplasmic CD 3. The antigen is one of the earliest to be expressed in T-cell differentiation and begins during the prothymocyte stage prior to entrance into the thymus. It is a T cell-specific surface marker normally present in resting and activated T lymphocytes. Cytoplasmic CD 3 expression is lost as common thymocytes differentiate into medullary thymocytes and the antigen is found only on the cell surface in postcortical T-cells but not in B cells, monocytes/macrophages, myeloid cells or any other cell type except for weak expression in Purkinje cells of the cerebellum. The polyclonal anti-CD 3 may produce weak staining of squamous epithelium and Hassal's corpuscles in the thymus but this lacks the distinct membrane ring-like pattern seen in T-cells and may represent weak cross-reactivity (Campana et al, 1989).

CD 3 is therefore a useful marker to distinguish precursor T-cell acute lymphoblastic leukemia/lymphoblastic lymphoma from their B cell counterparts and acute myeloid leukemia (Chetty & Gatter, 1994). CD 3 is a pan-T-cell lineage-restricted antigen, which is useful for labeling both neoplastic and non-neoplastic T-cells and surface CD 3 is expressed by all categories of postthymic T-cell lymphomas as well as lymphoblastic lymphoma but not lymphomas of B cell lineage. CD 3 may be aberrantly deleted in some peripheral T-cell lymphomas (Van Dongen et al, 1988; Cabecadas & Isaacson, 1991).

The appropriate antibody should be used for cytocentrifuge preparations as MoAb OKT3 (Ortho) detects surface CD 3 but not the cytoplasmic antigen in cytocentrifuge preparations. MoAbs Leu 4 (Becton Dickinson) and UCHT1 (Ancell, Immunotech, Sera Lab, Biodesign) detect cytoplasmic CD 3 in cytocentrifuge preparations and many other antibodies are not reactive at all in such preparations. The polyclonal CD 3 antibody is a useful reagent for paraffin-embedded sections as well as cytocentrifuge smears, especially following heat-induced epitope retrieval. It is reactive against both normal and neoplastic T-cells. CD 3 is absent in a subpopulation of T-cell neoplasms including cases of mycosis fungoides, pleomorphic small cell lymphoma, pleomorphic medium and large cell lymphoma and anaplastic large cell lymphoma. This may reflect aberrant gene expression by the malignant T-cells with loss of the antigen at the outset; alternatively, deletion may occur during the process of large cell transformation as seen in anaplastic large cell lymphoma (Picker et al, 1987).
A recently developed monoclonal anti-CD 3 clone (NCL-CD3-PS1) generated to a recombinant fusion protein representing thee subunit of the CD 3 molecule is reactive in paraffin-embedded sections and promises to be very useful but is currently not commercially available (Steward et al, 1997).

•Cabecadas JM, Isaacson PG 1991. Phenotyping of T cell lymphomas in paraffin sections which antibodies? Histopathology 19: 419-424.

•Campana D, Thompson JS, Amlot P, et al 1987. The cytoplasmic expression of CD3 antigen in normal and malignant cells of the T lymphoid lineage. Journal of Immunology 138: 648-655.

•Campana D, Janossy G, Coustan-Smith E et al 1989. The expression of T cell receptor-associated proteins during T cell ontogeny in Man. Journal of Immunology 142: 57-66.

•Chetty R, Gatter K 1994. CD3 structure, function, and role of immunostaining in clinical practice. Journal of Pathology 173: 303-307.

•Picker LJ, Weiss LM, Medeiros JL et al 1987. Immunophenotypic criteria for the diagnosis of non-Hodgkin's lymphoma. American Journal of Pathology 128: 181-201.

•Steward M, Bishop R, Piggott NH et al 1997. Production and characterization of a new monoclonal antibody effective in recognizing the CD3 T-cell associated antigen in formalin-fixed embedded tissue. Histopathology 30: 16-22.

•Van Dongen JJM, Krissansen GE, Wolvers-Tettero ILM et al 1988. Cytoplasmic expression of the CD3 antigen as a diagnostic marker for immature T-cell malignancies. Blood 71: 603-612.

Manual of diagnostic antibodies for immunohistology / Anthony S.-Y. Leong, Kumarasen Cooper, F. Joel W.-M. Leong.