Finally, we found persistently elevated anti-BK virus IgG titers and a specific anti-BKPyV T cell response.<h4>Conclusions</h4>This investigation showed evidence for the potential oncogenic role of BKPyV in collecting duct carcinoma in renal allografts and demonstrated that immunosuppression withdrawal and IL-2 therapy can lead to an efficient antitumor cellular mediated rejection possibly via 3 distinct mechanisms including (1) host-versus-graft, (2) host-versus-tumor, and (3) anti-BKPyV responses. The gene discussed is IL2; the disease is collecting duct carcinoma.