We have previously reported the establishment of cytotoxic T-cell lines, from pancreatic cancer patients, by continuously stimulating tumor-draining lymph node cells with allogeneic pancreatic tumor cell lines. After the preliminary characterization of their phenotype and tumor specificity, detailed studies performed with one of the cell lines, W.D., show that it recognizes a specific antigen, a large and heavily glycosylated mucin molecule, expressed on pancreatic and breast tumors and tumor cell lines. Although this recognition appears major histocompatibility complex (MHC)-unrestricted, the antigen receptor used by the cytotoxic T cell is the a/fl heterodimer, typically found on MHC-restricted T cells.The target antigen is atypical, however, in its ability to directly bind and activate the T cells in the absence of self MHC, presumably by abundant and regularly repeated antigenic epitopes. These rmfings are important because they demonstrate a specific T-cell response against a human tumorassociated antigen. In addition to pancreatic and breast tumors, various mucin molecules are known to be produced by other tumors of epithelial cell origin and could be expected to stimulate similar T-cell-mediated immune responses.

The high frequency of cytotoxic T-lymphocyte responses and the occurrence of clinical tumor regressions support continued investigation of multipeptide vaccines administered with GM-CSF in adjuvant.