To determine whether the newly developed anti-CD26 mAbs were suitable for immunohistochemical staining of CD26 in formalin-fixed tissue sections, surgically resected tissue specimens of normal liver, kidney, prostate, and malignant mesothelioma were immunostained with these mAbs, with commercial anti-CD26 mAb (purchased from MBL) and anti-CD26 pAb (purchased from R&D Systems) being used as controls. Here, DPP4 is linked to malignant mesothelioma.