Inflammation and Immune System Activation in Aging: A Mathematical Approach

Nikas, Jason B.

Biovariability of aging. It has long been observed empirically that aging is not a steady-state, uniformly continuous process; that it is characterized by a relatively wide biovariability; and that biological age may not necessarily coincide with chronological age. The results of my study corroborate those observations. Looking at the expression of the 36 most significant hippocampal genes of all 40 subjects Table 2 ). Moreover, the aforementioned observations about the biovariability of the aging process were also supported by the results of hierarchical clustering analysis performed on the F 1 scores of all 40 subjects (Supplementary Fig. 4) . 15 young subjects (Y) with respect to the house-keeping genes (a), and with respect to the 36 most significant genes (b). In (a), in connection with the house-keeping genes, the two groups are inseparable and indistinguishable; whereas in (b), in connection with the 36 most significant genes, the two groups are separated and are clearly distinguishable. D1 is subject distance from the centroid of cluster 1, and D2 is subject distance from the centroid of cluster 2. Inflammation and immune system activation in aging. Remarkably, of the 30 known genes out of the 36 most significant genes, 27 were -in terms of function -either genes of inflammation or genes of immune system activation (Table 1 ). This suggests that -to a large extent, and insofar as it pertains to the hippocampal area of the brain -the dual process of a chronic inflammation and the elicited chronic immune-system response and activity can differentiate between old and young brains with a high accuracy. This is further supported by the fact that the aforementioned seven genes employed by the F 1 super variable, all of which are genes of inflammation or genes of immune system activation, can discriminate between old and young brains with almost a perfect accuracy [sensitivity 5 (24/25) 5 0.96 and specificity 5 (15/15) 5 1.00].