Use of a panel of monoclonal antibodies for the diagnosis of hairy cell leukaemia. An immunocytochemical study of 36 cases

The phenotype of 36 cases of hairy cell leukaemia has been investigated using a panel of monoclonal antibodies reactive with normal human lymphoid cells and with hairy cells. Staining was performed on frozen sections and/or cell smears by the recently developed APAAP immuno‐alkaline phosphatase procedure. In about 90% of cases, neoplastic cells reacted strongly with antibodies against HLA‐DR, leucocyte common antigen, B‐cells (antibodies B1 and To15), hairy‐associated antigens (antibodies KB‐90, S‐HCL3, HC2) and activated T‐lymphocytes (antibodies anti‐Tac and Tü69). The phenotype of 10% of cases was clearly different in that the neoplastic cells were negative or only weakly positive for one or more of the antigens recognized by HC2, anti‐Tac and Tü69. Antibody HC1 reacted with tumour cells of only 50% of the hairy cell leukaemia cases investigated. Monoclonal antibody Ki‐67 (which selectively detects proliferating cells) stained only a low percentage of cells in all but three of the cases studied. The neoplastic cells in all cases were unreactive with monoclonal antibodies