Expression of leukemia-associated antigen, JL1, in bone marrow and thymus

The identification of immunophenotypic markers with restricted expression h as long been a critical issue in diagnostic and therapeutic advances for ac ute leukemias. We previously developed a monoclonal antibody against a new thymocyte surface antigen, JL1, and showed that JL1 is expressed in the maj ority of acute leukemia cases. In this study, using multiparameter flow cyt ometric analyses, we found that JL1 was uniquely expressed in subpopulation s of normal bone marrow (BM) cells, implying the association of JL1 with th e differentiation and maturation process, Although CD34(+) CD10(+) lymphoid precursors and some of maturing myeloid cells express JL1, neither CD34(+) CD38(-/lo) nor CD34(+) AC133(+) noncommitted pluripotent stem cells do. As for the myeloid precursors, CD34(+) CD33(+) cells do not express JL1, Duri ng lymphopoiesis, JL1 on the earliest lymphoid precursors disappear in the CD20(+) sIgM(+) stage of B-cell development or after CD1a down-regulation i n thymocytes, Despite the highly restricted expression of JL1 in normal BM cells, most of the leukemias express JL1 irrespective of their immunophenot ypes. These results indicate that JL1 is not only a novel differentiation a ntigen of hematopoietic cells, but also a leukemia-associated antigen. Ther efore, we suggest that JL1 be a candidate molecule in acute Leukemia for th e diagnosis and immunotherapy that spares the normal BM stem cells.