DPP4 and congestive heart failure: The pleural and serum CD26 levels in patients with tuberculous pleurisy were significantly higher than in patients with congestive heart failure.13 Immunohistochemical studies also revealed that CD26 is highly expressed in tuberculoid leprosy and sarcoidosis, known as Th1-like diseases.14 In our study, however, there was no significant difference in the serum levels of sCD26 between patients with sarcoidois and healthy volunteers.