A NOVEL MONOCLONAL-ANTIBODY, KOR-SA3544 WHICH REACTS TO PHILADELPHIA-CHROMOSOME-POSITIVE ACUTE LYMPHOBLASTIC-LEUKEMIA CELLS WITH HIGH-SENSITIVITY

A monoclonal antibody which primarily reacted with Philadelphia chromo some (Ph(1))-positive ALL cells was produced. The reactivity of a mono clonal antibody, KOR-SA3544 (IgG2a) was evaluated on normal hemopoieti c cells, 68 leukemic cell lines and freshly obtained cells from 190 pa tients with leukemia and lymphoma. in cultured cells, KOR-SA3544 react ed with Ph(1)-positive ALL cell lines (5/5) and leukemic cell lines wi th 11q23 translocation (3/11). In lymphoid cells, KOR-SA3544 was react ive with all of Ph(1)-positive ALL (26/26), a part of common ALL (5/38 ) and one case of early B precursor leukemia with 11q23 translocation, but not with peripheral lymphocytes. Normal mature granulocytes were also strongly stained. In myeloid leukemias, KOR-SA3544 was positive ( 16/56) only in patients with acute myeloid leukemia with FAB-MS and ov ert leukemia following myelodysplastic syndrome, but neither with othe r types of myeloid leukemias nor with blast crisis in chronic myelogen ous leukemia. KOR-SA3544 recognized a 90 KDa protein on the membrane o f a leukemic cell line, KOPN-57bi. In normal bone marrow, CD19(+)/KOR- SA3544(+) cells were not identified, while Ph(1)-positive ALL cells we re strongly positive for both antibodies. KOR-SA3544 is useful not onl y for making the diagnosis of Ph(1)-positive ALL but for detection of the minimal residual disease during remission.