PTPRC and prostate intraepithelial neoplasia: We examined the expression of CD45, a pan-leukocyte marker, and found that the percentage of CD45-positive (CD45+) prostate-infiltrating immune cells was increased in aged Nkx3.1−/− prostates compared with Nkx3.1+/+ prostates (3-fold increase at 12 months, P=0.02; n=3 per group; Fig. 1B,C and Table S1), which coincides with the occurrence of PIN in these mice.