MLH1 but not MSH2 protein is lost in individual CD34⁺ cells with age. (A) Percent of MLH1-positive stained CD34⁺ cells versus donor age (P = .0001). (B) Percentage of MSH2-positive stained CD34⁺ cells versus donor age (P = .55). Solid lines represent the best fit linear regression, and dashed lines signify a 95% confidence interval.