Impact of aging on innate immunity

Immune responses in higher organisms are triggered by the recognition of a limited diversity of microbiological products by cells of the innate or "na tural" immune system. As a result, in addition to the direct protective eff ect of natural immunity, antigen-presenting cells, particularly dendritic c ells, are activated to process and present an enormous number of peptide an tigens to the T lymphocytes of the adaptive immune system. These, together with the B lymphocytes, then mediate specific immune responses and maintain acquired immunological memory. The aging immune system is less well able t o cope with infectious disease than the youthful immune system; this review will briefly consider what is known of the age-associated alterations in i nnate immunity, and how these may also impact on adaptive immunity.