Comparison of size of the rapidly proliferating subpopulation (s₁) of cells in CD4 and CD8 T lymphocyte subsets. Significant differences between groups are indicated by the lines above the groups, together with the P values. Bar (black) represents the median value. One patient from CD4 effector memory and a different patient from CD8 naive subset were excluded from the analysis because of unusually high model estimates, statistically an outlier.