TNFRSF9 and neoplasm: Although we did not detect 4-1BB expression on the E.G7 tumor (data not shown) and anti-4-1BB is not thought to be depleting, to rule out a possible direct role of anti-4-1BB on tumor growth, we conducted a control experiment in which 4-1BB-deficient mice were implanted with the E.G7 tumor and then treated with anti-4-1BB on day 8 and day 11 post-tumor implantation, without any T cell transfer.