A monoclonal antibody, GR7A4, reacting with the T10 antigen

The monoclonal antibody GR7A4 was produced against a human lymphoblastic leukemia (ALL-B). Biochemical characterization of GR7A4 was carried out with Raji cells in SDS-PAGE studies. GR7A4 precipitated a 43 kd molecule. The tissue distribution and molecular weight were similar to the T10 antigen. Modulation and capping of GR7A4 antigen reduced its binding ability to cells with either GR7A4 or OKT10. However, the cell surface distribution pattern observed was somewhat different from other similar monoclonal antibodies. Thus GR7A4 reacted greatly with pre-B-cell lines, Burkitt cell lines, EBV cell lines and activated PHA, ConA and PWM lymphocytes, however reactivity with leukemic cells was very limited. The kinetics of appearance of GR7A4 antigen on PWM blasts show that this molecule seems to represent an intermediate stage in lymphocytic activation. The differences in comparison with other similar MAbs are discussed and correlated with the peculiar discontinous pattern of appearance of this antigen.