Given the reduced HI titers at 12 weeks postinfection with PR8-OVA and the importance of hemagglutination-inhibiting antibodies for protective immunity against influenza [19], we next evaluated the role of PAD2 in a rechallenge influenza infection using a viral dose of PR8 lethal to naïve DBA/1J mice. The gene discussed is PADI2; the disease is influenza.