Chloroquine has no effect on the presentation of HLA class I–restricted epitopes by RNA-transfected DCs. Autologous DCs were electroporated with MUC1 RNA alone (▪ in A, ♦ in B) and, after incubation with chloroquine, used as targets in a standard 51Cr-release assay (♦ in A, ▪ in B). MUC1-specific CTLs recognizing the M1.1 (A) or M1.2 (B) peptides were used as effector cells. DCs transfected with irrelevant EGFP RNA (▴) were included as controls.