Abstract
Adaptive immune system effects precise defense against a highly diverse array of microorganisms. For defense against new infections, the organism deploys naïve, previously antigen-unexposed, T and B lymphocytes, whose antigen-specific receptors recognize, and eventually orchestrate the removal of, the invading microorganisms. Naïve B, and even more so T, lymphocytes numerically diminish with aging. However, new data suggests that those that remain appear to have maintained their functional potential, contrary to an earlier dogma. To investigate cell-extrinsic defects in immunity, we studied aging of lymph nodes, including alteration in their architecture and stromal cell integrity, as well as changes in circulating factors. We will discuss how these components critically modulate both homeostasis and function of the aging immune system.