In support of this proposition, antibodies that deplete LAG-3+ lymphocytes prolong transplant survival in a rat cardiac allograft model,21 and abrogate Th1-driven inflammation in a delayed-type hypersensitivity challenge in non-human primates.22 Recently, single-cell RNA-sequencing of ileal biopsies from patients with Crohn’s disease found upregulation of LAG-3 expression in the cytotoxic T lymphocytes of the intestinal mucosa.23 Here, LAG3 is linked to Crohn disease.