This study shows that inflammageing, among others, the cytokine interleukin-15, indicates poor vaccine response. IL-15 is important for T cells and the biology of NK cells. Non-responders had higher frequencies of activated NK cells and total NK cells. 3/8

The role of NK cells was examined in mice. In the absence of IL-15, there are fewer T and NK cells. However, upon an inflammatory response, there is an improved response resulting in B cell stimulation and IgG1 antibody production (Tfh/Tfr ratio). 4/8