Differential presentation of tumor antigen‐derived epitopes by MHC‐class I and antigen‐positive tumor cells

SSX2 is a member of the family of cancer/testis antigens. The SSX2 derived peptide SSX2103–111 has been shown to be presented to cytotoxic T‐lymphocytes (CTL) by Major‐Histocompatibility (MHC) Class‐I complexes after endogenous processing, more precisely by the allele HLA‐A*0201. The HLA‐A*0201‐ and SSX2‐positive melanoma cell line SK‐Mel‐37 but not Me275 had been shown to elicit reactivity in SSX2103–111 specific cytotoxic T‐lymphocytes. To analyze the correlation between SSX2103–111 presentation and T‐cell stimulation, we intended to visualize presentation of SSX2103–111 in these melanoma cell lines. Fab‐antibodies were established from a human phage library with specificity for SSX2103–111/HLA‐A*0201 complexes (but non‐reactive with HLA‐A*0201 or SSX2103–111 alone) and used to visualize the presentation of SSX2103–111 in the context of HLA‐A*0201 by fluorescence microscopy. Presentation of SSX2103–111 the context of HLA‐A*0201 was demonstrated for the majority of SK‐Mel‐37, but for only a small fraction (