mb-1: A new marker for B-lineage lymphoblastic leukemia

Abstract

The expression of the Ig-linked mb-1 polypeptide was analyzed by immunocytochemistry (alkaline phosphatase anti-alkaline phosphatase technique) using a specific monoclonal antibody in 1 65 cases of acute leukemia, with 88 being lymphoblastic (ALL) and 77 myeloid (AML). The purpose of the study was to investigate the specificity of this reagent for B-lineage cases and its reactivity on leukemias that coexpress myeloid and B-cell antigens (biphenotypic). The majority (89%) of 72 B-cell precursor ALL patients were positive. Of these, mb-1 was expressed in all 9 patients with early-B-ALL (CD10-, cμ-), in all 11 patients with pre - B-ALL (cμ+) and in the single case of B-ALL (smlgM+7). Forty-three of 51 patients with common-ALL (CD10+, cμ+) were also positive. All 16 T-lineage ALL patients and 72 (93.5%) of the AML patients examined were mb-1 negative. Four of the 5 mb-1 -positive AML patients were considered biphenotypic and expressed other B-cell antigens such as CD10, CD19, and/or cCD22 and all showed rearrangement of the Ig heavy chain genes. Within the AML cases, mb-1 and cCD22 were more useful than other B-cell antigens in detecting biphenotypic cases, and mb-1 showed the highest correlation with the clonal rearrangement of Ig heavy chain genes. These results indicate that mb-1 is a sensitive and specific reagent for B-lineage blasts that will aid in the classification of B-cell precursor ALL and in the identification of biphenotypic leukemia presenting as AML. © 1993 by The American Society of Hematology.