Infection and sensitization reveal stimulus-specific immune remodeling in aged skin

Aging is linked to declines in skin barrier strength and immune defense, which makes older adults more prone to bacterial and viral skin infections. However, the specific ways aged skin detects and responds to infection or damage is not well understood. This study investigated the aged skin's immune response to epicutaneous Staphylococcus aureus infection and ovalbumin-induced sensitization in mice.

By analyzing the bulk RNA-seq of infected tissue, the researchers found that age primarily affects overall transcriptional variation, implying that older skin still reacts strongly to microbial threats. However, using microneedle patch sampling to examine skin interstitial fluid, which provides a cellular perspective, the team identified age-related differences in local immune dynamics following S. aureus infection.

These differences included changes in the intensity and timing of cellular recruitment, such as a weakened T cell response in older mice. Additionally, MNP profiling demonstrated that ovalbumin sensitization triggered a unique local immune program separate from the S. aureus response, which was not fully captured by systemic measurements.

Overall, these findings indicate that aging does not uniformly weaken cutaneous immunity; instead, it leads to a context-dependent reorganization of local tissue immune dynamics.