Monoclonal antibody against a differentiation antigen on human leukemia cells: cross-reactivity with rat leukemia and suppression of rat leukemia in vivo.

We produced a McAb against a normal differentiation antigen on human ANLL that cross-reacts with a rat ANLL. The McAb reacted with all ANLL cells tested as well as normal undifferentiated myelomonocytic cells. This McAb, of the IgM isotype, in the presence of C mediated lysis of human and rat leukemic cells in vitro. In addition, it mediated complete tumor suppression in rats engrafted with 10(2) to 10(3) rat leukemic cells in vivo. No significant side effects were observed in McAb-treated rats. McAb of this type may be useful in the treatment of human ANLL after conventional therapy, which often eliminates most leukemic cells, leaving a small number of residual cells. The ultimate utility of this McAb for human therapy or McAb directed against the same or other differentiation antigens remains to be determined.