Immune system(mice)

http://www.sciencedaily.com/releases/2010/01/100126101415.htm

"Thanks to the progress in health care and improved living conditions, we live longer. The price we pay: Our immune system loses functionality as we age and the susceptibility to infections increases. Members of the infection immunology research group at the Helmholtz Center for Infection Research in Braunschweig, Germany, are investigating this aspect of aging using a mouse model that mimics the susceptibility to infection observed in elderly humans."