Leukemic and normal hemopoietic cells were examined with the monoclonal antibodies DA2 and Genox 353 for the presence of HLA-DR and DR-linked (DC/MB) determinants, respectively. Although most non-T acute leukemias and leukemic cell lines expressed the monomorphic DR determinant deteced by DA2, fewer than expected expressed the DR-linked polymorphic specificity detected by Genox 353. TdT + lymphoid precursors from normal bone marrow were also DA2 + but Genox 353 -. T cells and thymocytes which were DA2 -, Genox 353 - became DA2 +, Genox 353 + after activation in vitro. Immunoprecipitation using DA2 and Genox 353 gave bands polyacrylamide gel-electrophoresis which were of different molecular weights. In addition, DA2 could absorb out Genox 353 detrminants from a cell lysate whereas Genox 353 could not absorb out DA2 determinants. It is concluded that DA2 and Genox 353 detect HLA-DR and DR-linked (DC1/MB1) determinants, respectively, and that these are differentially expressed on hemopoietic cells during differentiation.
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