Activation of cytotoxic T cells leads to the release of pro-inflammatory cytokines, such as IFN-γ, TNF-α, and IL-2, which can cause severe and unpredictable adverse effects such as the meningoencephalitis observed in patients immunized with AN1792, the first full-length Aβ vaccine, which contained the Aβ16-33 T-cell epitope (Monsonego et al., 2003; Orgogozo et al., 2003). This evidence concerns the gene TNF and meningoencephalitis.