(A and B) Lysis of homozygous or heterozygous HA-1–positive primary leukemic blasts by HA-1–specific CTL. HA-1^H peptide-specific CTL were induced in vitro from 2 different healthy HLA-A2–positive, HA-1–negative blood donors by monocyte-derived DC pulsed with synthetic HA-1^Hpeptide.2 DC were generated from adherent blood monocytes in the presence of GM-CSF, IL-4, and tumor necrosis factor  (TNF), as described.6 Leukemic HA-1–positive acute myelogenous leukemia (AML) or acute lymphoblastic leukemia (ALL) blasts from 6 different patients were used as target cells in a classical⁵¹Cr release assay.6 The HA-1–negative cell line “RR” pulsed with an irrelevant human immunodeficiency virus (HIV)-peptide was used as a negative control. Cell line “RR” (line 6574803) was kindly provided by Dr E. Goulmy (University of Leiden, Leiden, The Netherlands). (C) HA-1^Hpeptide-specific CTL do not cross-react with the HA-1^Rpeptide. CROFT is an HLA-A2⁺, HA-1^H/H–positive immortalized B-cell line, whereas U266 is an HLA-A2⁺, HA-1–negative (HA-1^R/R) myeloma cell line.