Discontinuous expression of a membrane antigen (HB‐7) during B lymphocyte differentiation

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Abstract
The expression of a cell surface antigen by B lineage cells in human fetuses, newborns and adults were examined using a newly produced monoclonal antibody, HB-7. The HB-7 antigen is a protease sensitive 45,000 MW molecule that appeared to be the same molecule recognized by the OKT-10 antibody. The HB-7 reactive molecule was expressed by all fetal pre-B and B cells, and 50% of newborn blood and adult bone marrow B cells. In contrast, only a small minority of B cells (2-12%) from blood, spleen and tonsil of adults were weakly HB-7+. The pokeweed mitogen-responsive B cell precursors of plasma cells were also HB-7-, but the HB-7 antigen was re-expressed during the plasma cell stage. This antigen is apparently unique among known B cell differentiation antigens in its intermittent pattern of expression during B cell development. The reactivity of the HB-7 antibody with immature, but not mature, B cells makes it well suited for studies of B cell ontogeny.