A team of scientists and physicians have discovered that the immune checkpoint protein VISTA can directly turn off tumor-fighting T-cells during immunotherapy and resist treatment. The study explains that VISTA can bind to a protein called LRIG1 in T cells, which was previously only thought to promote bone and fat development. When VISTA binds to LRIG1, the researchers found, LRIG1 sends signals that suppress T cell replication, survival and function. This interaction can happen between molecules on tumor cells and on T cells, molecules on healthy cells and T cells and even between molecules on the same T cell.