Fig. 2.

The Mart1 M26 epitope is poorly presented by CD40-B cells and dendritic cells, but efficiently presented by K562 cells. a In comparison with K562/A2 cells, CD40-B cells and dendritic cells (DC) expressing Mart1 antigen are poorly lysed by the Mart1 M26-specific T-cell clone. Europium-labeled HLA-A2+ target cells (5,000 target cells/well) were cocultured with the Mart1 M26 specific T-cell clone at an E:T of 1:1 and cytolysis measured by standard europium release assay. CD40-B targets pulsed with M26 peptide (black) but not control peptide (at 2 μg/ml, left panel, gray) were efficiently lysed. In contrast, target CD40-B cells nucleofected with full-length Mart1 RNA (black) or control RNA (20 μg, right panel, gray) were poorly lysed by the Mart1 M26 T-cell clone. In contrast, Mart1 RNA-nucleofected dendritic cells were moderately lysed by the T cells, while K562/A2 cells were efficiently lysed. Standard deviation <2.7%, DC versus K562A2 P = 0.0004. b. Mart1 protein is strongly expressed as a doublet after RNA transfer of full-length Mart1 into CD40-B cells, shown by immunoblot using a Mart1-specific monoclonal antibody. The melanoma cell line C32TG endogenously expressing Mart1 was used as a positive control