Leu-22: A Preferential Marker for T-Lymphocytes in Paraffin Sections: Staining Profile in T- and B-Cell Lymphomas, Hodgkin’s Disease, Other Lymphoproliferative Disorders, Myeloproliferative Diseases, and Various Neoplastic Processes

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Abstract
Monoclonal antibody Leu-22 represents an effective reagent for detection of neoplastic and nonneoplastic T-cells in paraffin sections of routinely processed tissues (242 specimens evaluated). In nonneoplastic tissues, immunoreactivity was localized mainly to lymphoid cells corresponding to a T-cell distribution. Immunoreactivity in lymphoid neoplasms, however, was preferentially, but not exclusively, limited to T-cell populations. Fifty-four of 60 T-cell neoplasms (90%) of various histologic types were Leu-22 positive. The pattern of immunoreactivity consisted mainly of membrane staining, with focal weak cytoplasmic positivity. Twenty-five of 67 B-cell neoplasms (37%) were also Leu-22 positive, with low-grade lymphomas (well/moderately well-differentiated lymphocytic types) representing most immunoreactive cases. In Hodgkin’s disease, although most small lymphoid cells were Leu-22 positive, only rare Reed-Sternberg cells were immunoreactive. In all cases, histiocytes and myeloid cells exhibited variable immunoreactivity. The epitope identified by Leu-22 was detectable in formalin- and B5-fixed tissues but apparently was denatured after fixation in Zenker’s–acetic acid solution used for bone marrow biopsies. Evaluation of a wide variety of nonhematopoietic neoplasms (64 total) revealed diffuse cytoplasmic staining in a few cases. However, membrane staining, typically noted for lymphoid cells, was not observed. Leu-22 potentially represents a useful marker for lymphoid cells, preferentially of T-cell origin, with optimal applicability as part of a panel that includes an effective pan-B-cell marker.

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