Effector cells isolated from the infused patients specifically kill GMCs. PBMCs isolated from the patients listed in Table 1 at the indicated time to HSCT were stimulated with GMCs from the respective HSC donors (○, ●) and with allogeneic T cells (□, ■). Lytic activities of the responder lymphocytes were measured against stimulator cells (■, ●) and untransduced HSC donor T cells (○, □) in a standard chromium-release assay at the indicated E/T ratios. Detection of positive immune responses against GMCs with the appropriate controls were reported.