Gene expression profile of resistant vs. sensitive PDA cells revealed the overexpression of several genes associated with immune tolerance such as indoleamine 2, 3-dioxygenases-1 (IDO1), cyclooxygenase 1 and 2 (COX1/2), adenosine deaminases acting on RNA (ADAR1), and galectin-9 (Gal-9). The gene discussed is IDO1; the disease is Patent ductus arteriosus.