Fig. 4 |. Immune cell dynamics in older adults yield a convergence on an attractor point.

a, Some cell subsets exhibit baseline-dependent dynamics, enabling inference of an attractor point corresponding to the stable frequency on which the system converges, along with a corresponding confidence interval (shaded box). b, A generalized model of cell-subset dynamics in healthy aging enables classification of cell subsets into three classes that differ in their ordering of reaching the attractor points: slow linear, asymptotic and fluctuating. c-e, Annual change versus baseline scatter plots along with annual change versus density distribution plots of three representative cell subsets assigned to the different classes. CD85j⁺CD8⁺ T cells (P_{annual change} = 343 × 10⁻⁸) naive CD4⁺ T cells (P_{annual change} = 594× 10⁻⁵ P_{liner model} = 5.33 × 10⁻⁷) and monocytes (P_{annual change} = 0.14) were classified as slow linear, asymptotic and fluctuating, respectively. Dashed orange and purple lines correspond to median abundance in old and young adults, respectively, whereas red line and shaded box correspond to attractor point and the confidence interval, respectively. f, Cell-subset classification along with the median cellular frequencies measured in young (purple, n = 63 individuals) and older (orange, n = 72 individuals) adults. For the asymptotic cell subsets, attractor point and corresponding confidence interval are in red. g, Ordering of asymptotic cell-subset modules by the time at which they reached attractor-point levels. Color represents first visit in which the cell subset reached the attractor point within an individual. Cell-subset assignments into modules appear on top. AP, attractor point.