A marked reduction in the TGF-β1/TNF-α ratio was observed in young adult individuals with DS compared to age- and sex-matched HC (Figure 6A, p < 0.001), and a diminished TGF-β1/TNF-α ratio was evident in older adult individuals with DS, with and without AD, when compared to HC in the 35–60 years age group (Figure 6B, p < 0.01 for older adult DS (35–60 years) vs. HC, p < 0.05 for DS-AD (35–60 years) vs. HC). This evidence concerns the gene TGFB1 and Alzheimer disease.