PTPRC and Brain atrophy: Second, the evaluation of the number of isolated CD45+ brain cells in aged SAMP8 compared to SAMR1 control (as shown in Fig. 5), allowed us to conclude that, at the age evaluated (10 m), there was not a significant increase of hippocampal Iba1+ cells in the old senescent animal SAMP8, with clear hallmarks compatible with brain degeneration.