The production of 9 cytokines (IFN-γ, TNF-α, IL-2, IL-4, IL-10, IL-17, IL-21, TGF-β, GM-CSF) following in vitro stimulation of PBMCs with tetanus (Fig. 5a and c) and diphtheria (Fig. 5b and d) toxoid was analyzed, and was found to be similar in young (Fig. 5a and b) and elderly (Fig. 5c and d) adults. This evidence concerns the gene IL17A and tetanus.