Abstract
SSX2 is a member of the family of cancer/testis antigens. The SSX2 derived peptide SSX2~103–111~ 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 SSX2~103–111~ specific cytotoxic T‐lymphocytes. To analyze the correlation between SSX2~103–111~ presentation and T‐cell stimulation, we intended to visualize presentation of SSX2~103–111~ in these melanoma cell lines. Fab‐antibodies were established from a human phage library with specificity for SSX2~103–111~/HLA‐A*0201 complexes (but non‐reactive with HLA‐A*0201 or SSX2~103–111~ alone) and used to visualize the presentation of SSX2~103–111~ in the context of HLA‐A*0201 by fluorescence microscopy. Presentation of SSX2~103–111~ the context of HLA‐A*0201 was demonstrated for the majority of SK‐Mel‐37, but for only a small fraction (<1%) of Me275 as indicated by a clear membrane‐staining pattern in fluorescence microscopy. The presentation of SSX2~103–111~ on SK‐Mel37 and Me275, but not the expression of the SSX2 protein correlated with the capability of these cells to stimulate cells of an SSX2~103–111~‐specific T‐cell clone. MHC‐peptide specific antibodies are a valuable tool for the analysis of antigenic peptides in the context of MHC‐I molecules and for the structural definition of immunodominant epitopes. © 2008 Wiley‐Liss, Inc.