Abstract: Methods for isolating polynucleotides encoding antibodies against lesional tissues are provided, wherein the methods comprise the steps of: (a) isolating a B cell(s) that infiltrates into a lesional tissue of interest; and (b) obtaining an antibody-encoding polynucleotide from the isolated B cell(s). The lesions may be a cancer tissue or such. Antibody genes can be obtained without depending on B cell cloning. Accordingly, it is also possible to obtain genes encoding human-derived antibodies which are difficult to clone. Genes that encode antibodies against cancer can be obtained using cancer tissues as the lesion.