[Immunosenescence and infections, myth or reality?].

The susceptibility of elderly people to infectious diseases is usually associated to increasing risk factors found in young adults. However, the role of immune function ageing is associated with the decline of immune function but this decline is not homogenous. Some functions such as the cellular immune system are altered but others are enhanced such as innate immunity. The important events of immune ageing are modifications of lymphocyte subsets with accumulation of memory cells, decrease in proliferative response, and a chronic inflammatory state. The chronic antigenic load throughout life is responsible for gaps in the antigenic system with a greater sensitivity to new antigens. These immune system changes are all the more important that diseases are severe and that denutrition is associated. These diseases will speed up the ageing process. The interaction between immunosenescence and pathology is an important phenomenon to consider. This review outlines the immune system changes due to ageing, their relationship with diseases of the aged patient, and the consequences of these modifications on vaccination effectiveness.