Exogenous kynurenines inhibit GVHD lethality. (A) Wt B6 mice were lethally irradiated and infused with BALB/c BM with or without 3 × 10⁶ T cells. On day 7, when weight loss was apparent, recipients were started on daily intraperitoneal injections of PBS (■) or 75 mg/kg of a mixture of L-kynurenine, 3-hydroxyanthranilic acid, and 3-hydroxykynurenine (□). Day 60 survival is shown, n = 5-6 mice/group. P = .03. (B) Treatment of mice from panel A was discontinued after 60 days. Long-term survival of mice surviving the first 60 days is shown. (C) Weight curves from the mice in panel A.