51 T cell lines/clones were established from tumor-infiltrating lymphocytes of nine breast tumors by limiting dilution. All the lines/clones were exclusively CD3+ and expressed either CD4 (57%) or CD8 (26%) phenotype. In addition, 17% of the lines/clones displayed a dual expression of CD4+CD8+ antigens. No CD3-CD16+ NK clones were obtained. A vast majority of the T cell lines and clones (84%) exhibited cytolytic activity in a lectin-dependent assay which allows the detection of cytolytic T cells of any antigen specificity. 17% of the lines/clones lysed two allogeneic breast tumor cell lines, MCF-7 and HBL-100. 11% of the cells showed NK-like cytolysis by lysing an NK-sensitive cell line K562. Of the 17 lines tested against autologous tumor cells, only two exhibited cytolytic activity via T cell receptor and CD3 molecule in an MHC-restricted manner. Southern blot analysis of T cell receptor of 39 lines/clones revealed a limited heterogeneity of TCR-B chain gene rearrangements, which suggests oligoclonal expansion of T cells infiltrating into the tumor.

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