To characterize the specificity of local B cells at the tumor site, we performed ex vivo cultures of NSCLC-infiltrating B cells and showed that they were able to produce high levels of IgG and IgA directed against tumor antigens of the cancer-testis antigen family, such as LAGE-1, MAGE antigens, and NY-ESO-1, but also P53. The gene discussed is TP53; the disease is cancer.