NCAM1 and neoplasm: hI-con1-mediated tumour cell lysis depends on the presence of effector cells (Hu et al, 1999; Hu and Garen, 2000, 2001), and CD56-positive lymphocytes have been shown to contribute most to the effect of IgG1-mediated antibody-dependent cell-mediated cytotoxicity in vitro as well as in vivo (Ortaldo et al, 1987; Clynes et al, 2000).