HAVCR2 and viral infectious disease: Positive expression of iRs such as PD1, CTLA-4, TIM3, LAG-3, 2B4, CD160, and BTLA has been directly linked to reduced cytokine production by T cells from cancer patients (including reports from our group) or in the chronic LCMV mouse model of “T cell exhaustion” and other viral infections (7, 13, 19–23).