We analyzed the T-cell repertoires from the bone marrow of 39 primary operated breast cancer patients and 11 healthy female donors for the presence and frequencies of spontaneously induced effector/memory T lymphocytes with peptide-HLA-A2-restricted reactivity against 10 breast tumor-associated antigens (TAA) and 3 normal breast tissue-associated antigens by short-term IFN-gamma enzyme-linked immunospot (ELISpot) analysis. Sixty-seven percent of the patients recognized TAAs with a mean frequency of 144 TAA reactive cells per 10(6) T cells. These patients recognized simultaneously an average of 47% of the tested TAAs. The T-cell repertoire was highly polyvalent and exhibited pronounced interindividual differences in the pattern of TAAs recognized by each patient. Strong differences of reactivity were noticed between TAAs, ranging from 100% recognition of prostate-specific antigen(p141-149) to only 25% recognition of MUC1(p12-20) or Her-2/neu(p369-377). In comparison with TAAs, reactivity to normal breast tissue-associated antigens was lower with respect to the proportions of responding patients (30%) and recognized antigens (27%), with a mean frequency of only 85/10(6) T cells. Healthy individuals also contained TAA-reactive T cells but this repertoire was more restricted and the frequencies were in the same range as T cells reacting to normal breast tissue-associated antigens. Our data show a highly individual T-cell repertoire for recognition of TAAs in breast cancer patients. This has potential relevance for T-cell immune diagnostics, for tumor vaccine design, and for predicting immune responsiveness.