Figure 5. Age- dependent HOXA5 protein decline. HOXA5 protein levels are significantly down-regulated in monocytes from old blood donors. (A) HOXA5 protein quantities were determined by ELISA in total cell lysates of monocytes isolated from young and old blood donors expressed as ng per mg total protein. Error bars denote SEM (n = 30, average age: 23.0 yrs and 81.1 yrs, respectively). (B) Delineates a linear correlation between HOXA5 protein expression and the participants age showing decreasing protein levels with increasing age as reflected in the respective correlation coefficient (r = -0.5357). (C) Twenty-five micrograms of total cell lysates from monocytes isolated from young and old blood donors were subjected to immuno-protein gel blotting with rabbit monoclonal anti-human HOXA5 antibody ab140636 (1:500), recognizing the HOXA5 protein at 42 kDa (predicted molecular weight 29 kDa). ß-actin served as loading control. (D) delineates a linear correlation between HOXA5 expression (ng per mg total protein) and HOXA5 methylation in the target CpG site of the promoter region showing decreasing protein levels with increasing methylation as reflected in the respective correlation coefficient (r = -0.5070).