Surface immunoglobulins and protease inhibitors of human acute leukemia blasts

Abstract

Cell-surface proteins of human leukemic blasts were studied by direct immunofluorescence (DIF), low pH elution and immunodiffusion (ID). Among A M L blasts from 21 patients, the average proportions of blasts positive for IgG, IgM, and IgA were 60%, 9%, and 9% respectively. I n contrast, blasts from four CML patients in blast crisis and 14 A L L patients had surface IgG, IgM, and IgA values of 14%, 9%, and 7% respectively for the former group and 1.4%, 1.1%. and 0.8% respectively for the latter group. Blasts from 20 leukemic cell preparations were eluted at pH 2. The Fab reaction product is incapable of interacting with either complement or Fc receptors. Therefore, such proteolytic activity may protect the leukemic blasts from lysis by complement-dependent o r antibody-dependent cell-mediated cytotoxic mechanisms.