Human T-lymphoid cell line Jurkat was treated with actinomycin D (ActD) and cycloheximide (CHX). The induction of apoptosis was confirmed by the chromatin condensation and DNA ladder fragmentation. Anti-band 3 IgG, purified from normal human plasma, bound to the ActD- or CHX-treated cells, and the binding was correlated to the degree of apoptosis. Antioxidants, N-acetylcysteine, pilloridine dithiocarbamate, and trolox, inhibited neither induction of DNA fragmentation of ActD-treated cells nor anti-band 3 IgG binding to ActD-treated cells, indicating that formation of the anti-band 3 IgG; binding sites on the apoptotic cell surface is caused by nonoxidative mechanism. When Jurkat cells were treated with endo-beta-galactosidase to cleave sialylated poly-N-acetyllactosaminyl saccharide chains from the cell surface before induction of apoptosis, the binding of anti-band 3 IgG was abolished. The results indicate that sialylated poly-N-acetyllactosaminyl saccharide chains on the cell surface are requisite for the binding of anti-band 3 IgG to apoptotic cells.