Enhanced breakdown of TRP leading to the production of biologically active metabolites has been demonstrated in vivo under inflammatory conditions, during the rejection of transplanted tumors or in cancer patients treated with interferon-gamma (IFN-γ) [35], and the TRP catabolite, picolinic acid (PA), was found in the serum of patients with liver cirrhosis [22]. The gene discussed is IFNG; the disease is cirrhosis of liver.