ITIM-dependent GO-induced cytotoxicity in transduced cell lines. (A) 32D cell sublines, (B) OCI-AML3 cell sublines, and (C) KG-1a cell sublines transduced with either wild-type CD33 or CD33 mutants were incubated with indicated concentrations of GO for 3 days, before cytotoxicity was assessed with PI staining. In the case of KG-1a sublines, cells were cotreated with CSA. Increases in the percentage of PI-positive cells in GO-treated cells are compared with corresponding cells that were incubated without GO, and results are shown as mean ± SEM from 2 to 5 independent experiments performed in duplicate or quadruplicate wells. The left panels show the data grouped for individual sublines, whereas the right panels show the effect of GO-induced cytotoxicity in relation to the percentage of internalization of CD33 after 2 hours.