CD 1

Accurate (WM35-1a), Becton Dickinson (Leu5), Biodesign (ALB1, ALB2), Biogenesis (DMC1), Biogenex (T6-1a), Bioprobe, Biosource (BB5), Boehringer Mannheim (YIT6), Caltag Lab (66-11-C7, VIT66-1a), Coulter (T6), Cymbus Bioscience (CBNT6-1a), Dako (NA1/34), Immunotech (010), Oncogene, Sanbio (66-11-C7), Serotec (4A76, NAI-34-1a), Seralab (CD 1) and Immunotech (CD 1a).

Fresh-frozen tissues. CD 1a (clone 010) is effective in paraffin-embedded tissues, with immunoreactivity enhanced by HIER.

Human CD1 genes are a family of five non-polymorphic genes that, although homologous to both class I and II major histocompatibility complex genes, map to chromosome 1. Four isoforms of the CD 1 proteins have been clustered, namely CD 1a, -b, -c and -d and are expressed on the surface of cells in association withb 2-microglobulin and may function as non-classic antigen-presenting molecules. While CD 1 genes have been found in a wide variety of vertebrates, they have shown differences in size and complexity in different mammals. Most CD 1 molecules can be separated into two groups based mainly on homology of nucleotide and amino acid sequences. Group 1 includes the human CD 1a, -b and -c proteins, which are the classic CD 1 antigens first identified on human thymocytes and now recognized on a variety of specialized Ag-presenting cells, including dendritic cells in lymphoid and non-lymphoid tissues. These proteins can also be induced in vitro on virtually all circulating human monocytes by exposure to granulocyte-macrophage-CSF, suggesting that they might be upregulated on tissue macrophages in many inflammatory lesions. The Group 2 CD 1 proteins include the human CD 1d and mouse CD 1, which so far have been found to be most prominently expressed by gastrointestinal epithelia and B lymphocytes (Boumsell, 1989). CD 1a, -b and -c are expressed in about 70% of all thymocytes, predominantly the cortical thymocytes.
CD 1 is not expressed in early thymocytes or by mature resting or activated T lymphocytes. This distribution is reflected by neoplastic populations of T cells in that precursor T-ALL/LBLs expressing cortical or immature phenotypes are CD 1+, in contrast to those with prothymocyte or medullary thymocyte phenotypes. All postthymic or T dt-negative T-cell neoplasms such as T-CLL, T-PLL, Tg-lymphoproliferative disorder, Szary syndrome, cutaneous T-cell lymphoma and node-based T-cell lymphoma are consistently negative for CD 1 (Porcelli & Modlin, 1995).

CD 1a, CD 1b and CD 1c antigens are membrane glycoproteins with MWs of 49 kD, 45 kD and 43 kD, respectively. Their expression on thymocytes and also on a variety of antigen-presenting cells including Langerhans cells and interdigitating dendritic cells makes detection, particularly of CD 1a, useful in the diagnosis of Langerhans cell histiocytosis and the classification of thymomas and malignancies of T-cell
precursors. CD 1a is a specific marker for Langerhans cells (Shinzato et al, 1995). Thymic lymphocytes that are CD 1+ represent cortical thymocytes.

Antibodies to CD 1a are useful in diagnosis of Langerhans cell histiocytosis, in the classification of thymomas and malignancies of T-cell precursors. While most of the antibodies available are only reactive in fresh-frozen tissues, a recently developed antibody to CD 1a, clone 010, is reactive in paraffin sections following heat-induced epitope retrieval and is available through Immunotech (Krenacs et al, 1993).

•Boumsell L 1989. Cluster report: CD 1. In: Knapp W, Dorken B, Reiber EP et al. (eds) Leucocyte typing IV: white cell differentiation antigens. Oxford: Oxford University Press, pp 251-254.

•Krenacs L, Tiszalvicz LT, Krenacs T, Boumsell L 1993: Immunohistochemical detection of CD1a antigen in formalin-fixed and paraffin-embedded tissue sections with monoclonal antibody 010. Journal of Pathology 171: 99-104.

•Porcelli SA, Modlin RL 1995. CD 1 and the expanding universe of T cell antigens. Journal of Immunology 55: 709-710.

•Shinzato M, Shamoto M, Hosokawa S et al 1995. Differentiation of Langerhans cells from interdigitating cells using CD1a and S-100 protein antibodies. Biotechnology and Histochemistry 70: 114-118.

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