Characterization of a new monoclonal antibody 6G7 that recognizes a unique antigen on myeloid and lymphoid cells.

We generated a monoclonal antibody (mAb) 6G7, which recognizes a 220-kD antigen on selected subpopulations of normal myeloid and lymphoid cells and their malignant counterparts. 6G7 reacts with 90-95% of peripheral blood B cells, 70-80% of CD8(+) cells, 30-35% of CD4(+) cells, 20-40% of monocytes, and 20-40% of CD34(+) cells from bone marrow. 6G7 reacts with leukemic blasts in acute myeloid leukemia (14/16), adult acute lymphoblastic leukemia (ALL) (5/5), pediatric ALL (5/9), chronic lymphocytic leukemia (8/8), follicular lymphoma (7/7), and Burkitt's lymphoma (1/1). Long-term bone marrow culture of 6G7(+/-) cells showed the majority of clonogenic hematopoietic cells were in mAb 6G7 subpopulation. An immunotoxin of 6G7 and ricin A chain was cytotoxic to 6G7(+) leukemia cell lines. mAb 6G7 has potential clinical applications for targeted immunotherapy of both leukemia and lymphoma.