Monoclonal antibodies reactive with human myeloid leukaemia cells

Hybridomas producing monoclonal antibodies that bind to determinants on myelogenous leukaemia blast cells were developed using fresh leukaemia blasts as immunogens. These monoclonal antibodies were used to quantitate the amount of a variety of antigens on both leukaemia and normal blood cells in a radioimmunoassay. The ability of these antibodies to mediate complement-dependent lysis of leukaemia cells and normal blood cells was evaluated. Significant quantitative differences in the expression of a variety of cell surface antigens were observed among different myeloid leukaemia cell samples, normal cells, and other forms of leukaemia. However, none of the monoclonal antibodies studied were found to be specific for myeloblasts. Despite the fact that these antibodies bound to both leukaemia and normal cells, several of them mediated complement-dependent cytotoxicity which was restricted to leukaemic myeloblasts (AML-1-211, AML-2-30, CML-18, CML-75, CML-115, and CML-150). None of these clones, alone or in any combination, were capable of lysing normal lymphocytes or monocytes. Others were specifically cytotoxic to leukaemia cell lines (AML-1-99), B cells and some leukaemia samples (AML-2-9), and myelomonocytic leukaemia cell samples and normal monocytes (AML-2-23). Several of the monoclonal antibodies from this panel appear to be promising for future clinical applications.