MHC class I-restricted CTLs specific for antigens expressed by malig nant cells are an important component of immune responses against human cancer. Recently, in melanoma a number of melanocyte differen

MHC class I-restricted CTLs specific for antigens expressed by malig nant cells are an important component of immune responses against human cancer. Recently, in melanoma a number of melanocyte differen tiation antigens have been identified as potential tumor rejection antigens. In the present study, we show that by applying peptide-loaded dendritic cells, induced by granulocyte-macrophage colony-stimulating factor and interleukin 4 from peripheral blood monocytes ofhealthy donors, we were able to elicit melanoma-associated antigen-specific Cli in vitro.We dem onstrate the induction of CTLs directed against HLA-A2.1 presented epitopes derived from tyrosinase, gplOO, and Melan A/MART-i. Apart from lysis of peptide-loaded target ceHs,these CTLs displayed reactivity with HLA-A2.1' melanoma tumor cell lines and cultured normal mela nocytes endogenously expressing the target antigen. These data indicate thattheseCTLsrecognizenaturallyprocessedandpresentedepitopesand that precursor CTLs against melanocyte differentiation antigens are pres ent in healthy individuals. The ability to generate tumor-specific CTLs in vitro, using granulocyte.macrophage colony-stimulating factorrmterleukin 4-induced dendritic cells, illustrates the potential use of this type of antigen-presenting cells for vaccination protocols in human cancer.