Study hints at why older people are more susceptible to the flu

An inflammatory lipid appears to reduce the number of macrophages inside the lungs with age. The study, led by first author Judy Chen, a Ph.D. candidate, senior author Daniel Goldstein, M.D., the Eliza Maria Mosher Collegiate Professor in Internal Medicine and Professor of Microbiology and Immunology, and their team investigates why cells called alveolar macrophages, the first line of defense in the lungs, appear to be compromised with age.These macrophages are immune cells that attack invaders like the flu virus and live in the small air sacs, or alveoli, inside the lungs. Importantly, these cells appear to be lost with aging. Previous research by another group showed that when macrophages from an old mouse were put into a young mouse, and cells looked young again. “This drove us to believe that something in the environment of the lungs is contributing to this,” said Chen.Signs pointed to a lipid immune modulator known as prostaglandin E2 (PGE2) with wide ranging effects, from labor induction in pregnancy to inflammation with arthritis.The study team discovered there is more PGE2 in the lungs with age. This increase in PGE2, Chen explained, acts on the macrophages in the lung, limiting their overall health and ability to generate.The team suspects that the buildup of PGE2 is yet another marker of a biological process called senescence, which is often seen with age. Senescence serves as insurance against the runaway division of damaged cells; cells that are senescent are no longer able to replicate. “One of the interesting things about these cells is they secrete a lot of inflammatory factors,” said Chen.