As individuals age, their ability to respond to and clear pathogens and to control unwanted immune reactions declines, leading to a greater incidence of certain infectious diseases, autoimmunity and general immune dysfunctions. Most remarkably, the efficacy of vaccines is frequently decreased in elderly persons. Therefore, age-associated dysfunctions of the humoral and cellular immune responses have a strong clinical impact. Improving our understanding of the aged immune system is crucial in developing effective prevention and treatment programs that will facilitate healthy aging and...