A monoclonal antibody specific for immature human hemopoietic cells and T lineage cells.

An anti-human monoclonal antibody (RFB-1) has been produced that reacts with a group of hemopoietic precursor cells in human bone marrow. These include terminal deoxynucleotidyl transferase-positive (TdT+) cells and myeloid colony-forming unit cells, functionally identifiable progenitor cells of the granulocytic-monocytic series. The expression of RFB-1 antigen on myeloid cells decreases as the cells become more mature; myeloblasts are weakly RFB-1+ but most promyelocytes are RFB-1-. RFB-1 also reacts with TdT+ thymic blast cells and cortical thymocytes but is unreactive with TdT- medullary thymocytes, although the majority of peripheral T cells are weakly RFB-1+. RFB-1 is the first anti-precursor cell reagent that labels human TdT+ cells in both the thymus and bone marrow as well as hemopoietic precursor cells but is unreactive with pre-B blasts and B lymphocytes.