Fig. 1

Immune alteration during physiological aging. Physiological aging is associated with a series of immune-related modifications that could contribute to age-associated diseases like respiratory virus infections. Inflammaging describes a progressing low-level inflammation associated with age. A feed-forward circuit is formed between senescent cells and inflammaging. In the lung, dysfunctional surfactant turnover by type II airway epithelial cells (AT II) and alveolar macrophages (AMs) could also lead to persistence of oxidative and pro-inflammatory molecules in the alveolar lining fluid. Moreover, an age-associated decline in the naïve lymphocyte pool, attributed to myeloid bias of HSC cells and thymic involution, could abrogate successful defense against respiratory viruses