The world population is undergoing a rapid expansion of older adults, and thus, exploring how to stay healthy with age has become an urgent global focus. Aging leads to numerous physiological changes, including the deterioration of the immune system, rendering the elderly more susceptible to infections, such as the COVID-19 pandemic, and poor responses to vaccines (Ciabattini et al., 2018; Alpert et al., 2019; Onder et al., 2020; Verity et al., 2020). Changes observed during aging are often reflected as alterations in the composition and functional declines of diverse immune cells. For T cells (TCs), the high frequency of naive cells in young humans progressively decreases along with the accumulation of highly differentiated memory cells (Hakim and Gress, 2007), whereas nonclassical monocytes (MCs) with high levels of plasma tumor necrosis factor (TNF)-α and interleukin (IL)-8 accumulate with age (Ong et al., 2018). In addition, senescence of the immune system in the elderly has been termed “inflammaging”, which refers to increased levels of tissue and circulating proinflammatory cytokines in the absence of an immunological threat (Panda et al., 2009; Franceschi et al., 2018). Overall, aging is associated with changes in the structure of diverse immune compartments, where accumulating dysfunctional subsets contribute to immune failure.