Daan Pieren

21 General introduction and scope of this thesis identifying novel combinations of age-related markers on CD8 + T cells and their relationship to the three differentiation stages described for CD8 + T cells, based on expression of co-stimulatory receptors CD28 and CD27. In chapter 5 , we continue our search for novel age-related effects on the human CD8 + T-cell population. In this chapter, we identify a new human CD8 + T-cell subset that remained hidden within the virtual memory T cell subset (an innate-like population of CD8 + T cells that has recently been found to associate with aging). We named these CD8 + cells KIR + RA + T cells based on their expression of KIR and CD45RA. Here, we investigate the phenotype and function of KIR + RA + CD8 + T cells in young and older adults, and we address their relevance in a clinical setting in individuals that are suffering from respiratory viral infection, including Influenza A virus and the novel SARS-CoV-2. Lastly, chapter 6 of this thesis summarizes our findings, discusses our conclusions within the current literature and provides future perspectives based on our findings. 1