Figure 2. Intra-individual correlations: in vitro versus in situ p16INK4a positivity. Each dot represents an individual donor, N=52. In vitro p16INK4a positivity: percentage of p16INK4a positive cells - mean of experiments I and II. In situ p16INK4a positivity: number of p16INK4a positive cells per 1mm2 dermis. Uncorrected (not log transformed) data points are shown.