Hello Sandra, Both CD1a and S-100 are antigens usually detected in cytoplasm of large cells present in histopathological sections of biopsies (e.g skin changes in patients with Langerhans cell histiocytosis) or in cytological material from bone marrow or spleen fine needle aspirates (in hemophagocytic lymphohistiocytosis). These cells are normally present in the skin (Langerhans cells) but increase much in Langerhans cell histiocytosis. Also positive cells may be found in small numbers in normal spleen and bone marrow but increase in numbers and have high phagocytic activity in hemophagocytic lymphohistiocytosis. The most commonly used detection methods are immunostainings with mouse monoclonal antibodies to these antigens and immunoenzymatic methods, using anti-mouse Ig antisera labeled with peroxidase or alkaline phosphatase. The monoclonal antibodies connect to cells with CD1a or S100 and the antisera connect to these antibodies. We visualize the enzymes with various substrates getting color reaction so the positive cells will be brown, red or blue in the cytoplasm. I hope this helps, if anything is unclear please ask. Anna PS Happy New Year to everybody! At 22:26 2001-12-22 -0500, you wrote: > >Greetings: I have been referred here in hopes of finding some answers. >I am a website editor and scientific layperson, and I'm in the process >of creating a dictionary of histiocytic terms for families and patients >with Langerhans cell histiocytosis and hemophagocytic >lymphohistiocytosis. These are very rare diseases that are sometimes >fatal. There are several hallmarks for diagnosis, one being CD1a >positivity, another being presence of Birbeck granules on electron >microscopy and another being positive S-100 staining. I have read >numerous relevant articles but am unable to extrapolate a specific >definition for CD1a and S-100 as they relate to histiocytosis. I need a >concise definition that would be decipherable to a patient with this >illness. I also would like to know how these tests are done. Can anyone >help? > >Thanks, >Sandra Conway Warren > >-- >email: tryon3@concentric.net >email: sandra@histio.org >fax: +1 425 696 9392 (United States) > > > Anna Porwit Hematopathology Lab. Department of Pathology, Radiumhemmet Karolinska Hospital, 171 76 Stockholm, Sweden Anja.Porwit@ks.se tel.:+46-851774518 fax.:+46-851775843
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