Dr. Vijay K. Kuchroo of Harvard Medical School and the Broad Institute describes using RNA and protein expression profiling at single-cell resolution to identify a module of co-inhibitory receptors, which includes not only several known co-inhibitory receptors (PD-1, Tim-3, Lag-3, and TIGIT), but also a number of novel surface receptors. This enabled functionally validating a number of novel co-inhibitory receptors not previously associated with T cell dysfunction. Studies with a number of “novel” co-inhibitory molecules in regulating anti-tumor immunity and autoimmunity will also be presented. Explore: • What is the mechanism by which T cells are inhibited from inducing anti-tumor immunity? • Why doesn’t the “checkpoint” blockade induce complete anti-tumor immune response and tumor regression in all patients? • What are the soluble factors produced by T cells that inhibit anti-tumor immunity?