Lost lung immune cells increases susceptibility to flu in older adults

Why are older people more likely to fall ill with influenza (flu)? Research from the University of Michigan Medical School (U-M Medical) has revealed how the first line of defense against foreign pathogens known as alveolar macrophages, in the lungs, are compromised with age and cause increased susceptibility to the flu.

According to researchers led by postgraduate candidate Judy Chen and Dr. Daniel Goldstein, Professor in Internal Medicine and Professor of Microbiology and Immunology at U-M Medicine, a lipid immune modulator known as prostaglandin E2 (PGE2) buildup acts on the macrophages in the lung, limiting their overall health and ability to generate.

PGE2 is known to have wide ranging effects, from labour induction in pregnancy to inflammation with arthritis.

The researchers suspect that the buildup of PGE2 is yet another marker of a biological process called senescence, which is often seen with age. In short, cells that are senescent are basically unable to replicate.

“One of the interesting things about these cells is they secrete a lot of inflammatory factors,” said Chen.

The research showed that the cells lining the air sacs in the lungs (alveoli) become senescent with age, leading to increased production of PGE2 and suppression of the immune response.

To test the link between PGE2 and increased susceptibility to the flu, researchers treated older mice with a drug that blocks a PGE2 receptor. “The old mice that got that drug actually ended up having more alveolar macrophages and had better survival from influenza infection than older mice that did not get the drug,” said Chen.

The team plans to next investigate the various ways PGE2 affects lung macrophages as well as its potential role in inflammation throughout the body.

“As we get older, we become more susceptible not only to influenza, but to other infections, cancers, autoimmune diseases as well,” Chen pointed out.

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