What is interleukin-2 and why is the Saltikva bacterium engineered to make it?

Interleukin-2 (IL-2) is a signaling protein that activates immune cells such as natural killer cells and T cells. Salspera, Inc. engineered Saltikva to carry the human IL-2 gene, with the hope that IL-2 made near tumors could stimulate immune cells with less exposure elsewhere in the body than IL-2 given by injection. That idea is a hypothesis, and localized IL-2 release in tumors was not confirmed in patients in the Phase 2.