On Herpes

AT) and alpha-1-antichymotrypsin (a-1-ACT) have been shown to be better markers in malignant lesions.^-'' Similar to lysozyme, a-1-ACT and a-1-AT may be found in other cell lines, particularly those of myelocyte derivation.^ Recently, there have been reports of other cytoplasmic markers, such as peanut agglutinin^ and concanavalin agglutinin,'' v^hich appear to be specific for cells of histiocyte lineage. Histiocytes possess surface receptors for IgC, C3, IgE, and HLA-DR, but these are shared by other types of cells. The availability of monoclonal antibodies that may be used in conjunction with immunofluorescence or immunoperoxidase has, however, through the detection of specific cell surface determinants, enabled the labelling of histiocytes in tissue sections. The most widely used monoclonal antibody is OKMI (Ortho), although others have been produced.® These antibodies, while possessing more specificity, have one particular disadvantage—the limitation to frozen tissue sections—as standard fixatives may destroy cell surface determinants.® Dedifferentiation of malignant cells may also lead to loss of cell surface markers,' producing a false-negative result.