Enhanced staining for Leu M1 (CD15) in Hodgkin's disease using a secondary antibody specific for immunoglobulin M

The utility of staining for Leu M1 (CD15) as a diagnostic aid in Hodgkin's disease has been questioned because of a relative lack of specificity and sensitivity. Furthermore, interpretation is often made difficult by staining that tends to be weak and focal. Because the murine monoclonal anti-Leu M1 antibody is of immunoglobulin M type, it is reasonable to wonder whether improved immunohistochemical staining might result from use of a secondary goat antibody specific for the mouse mu heavy chain instead of the traditional one against mouse immunoglobulin. The two methods were compared, using a biotin-avidin detection system, on paraffin sections from 15 cases of Hodgkin's disease: 9 nodular sclerosing, 1 mixed cellularity, and 5 of nodular lymphocytic and histiocytic (L&H) type. In the nodular sclerosing/mixed cellularity group, the mu-specific detection method resulted in a greater number of cases with reactive Hodgkin's cells (7 versus 5), stained an average of more than three times as many neoplastic cells in each case (49% versus 14%), and usually produced staining that was distinctly more intense, often in a membrane and paranuclear distribution characteristic of Leu M1 in Hodgkin's cells. In the noLeu M1 in Hodgkin's cells. In the nodular L&H group, 1 case showed weak, focal staining with the newer method. None of the L&H cases stained using the traditional technique. It is concluded that use of a second-stage antibody that is directed specifically against mu heavy chains results in an improvement in immunohistochemical staining for Leu M1 in paraffin sections, which is of practical significance.