Immunodetection of annexin II from the cell surface of human leukemic cell lines. (A) Human leukemia cell lines were treated with either HBSS alone (lanes with a minus sign) or HBSS containing 4 mM CaCl₂ (lanes with a plus sign) for 30 minutes. Annexin II proteins were detected with specific antibodies. (B) The levels of mRNA and total and surface annexin II were determined by the band intensity of autoradiograms from Figures 1 and 5A. Amounts shown are relative to levels in the NB-4 APL cell line. AnnII/b-actin indicates ratio of annexin II mRNA to β-actin mRNA; annII(total), total annexin II protein; and annII(surface), surface annexin II protein. (C) 697/E2A-HLF cells and 697/pMT cells were cultured in medium with or without 100 μM Zn²⁺ as indicated for 16 hours before treatment with either HBSS alone (lanes with a Ca²⁺ minus sign) or HBSS/Ca (lanes with a Ca²⁺ plus sign). Annexin II proteins were detected using specific antibodies.