It has been proved that serums of patients with cancer have antibodies that may react with autoantigens called tumour associated antigens (TAA). The present study performed serum immunoproteomics of 25 patients with breast cancer stage II, and serums of 20 healthy donors for the detection of TAAs. The pre-clarified serum samples were subjected to a 2DE and transferred to a nitrocellulose (NC) membrane these were incubated with serums of patients with breast cancer and healthy donors. Comparing the patterns of Western-Blot of 2D, three proteins where recognised by the antibodies present in the serums of cancer patients and not by the serums of healthy people. The three proteins were obtained from the 2D gels, and were analysed by MALDI-MS. The results show that the protein is the alpha-1-atitrypsin (A1AT). An analysis 1DE of Western-blot is performed with the protein in order to confirm the presence of antibodies anti-A1AT in the serum of the patients, where 24 out of 25 were detected with breast cancer (96%) and 2 out of 20 were controls (10%). Our results suggest that the A1AT and antibodies against this protein are useful as markers for the detection of breast cancer and the diagnosis thereof in early stages.Se ha demostrado que sueros de pacientes con cáncer contienen anticuerpos que reaccionan con autoantigenos llamados antígenos asociados a tumor (AAT). En el presente estudio se realizó inmunoproteómica de sueros de 25 pacientes con cáncer de mama en etapa II, y sueros de 20 donantes sanos para la detección de AATs. Las muestras de suero pre-clarificadas se sometieron a 2DE y transfirieron a membrana de nitrocelulosa (NC), estas se incubaron con sueros de pacientes con Cáncer de Mama y donantes sanos. Comparando los patrones de Western-Blot de 2D, tres proteínas fueron reconocidas por anticuerpos presentes en los sueros de pacientes con cáncer y no por los de personas sanas. Las tres proteínas se obtuvieron de los geles de 2D, se analizaron por MALDI-MS. Los re
