Fig. 1.

DPP4 expression and enzymatic activity contributed by immune cells.

A, DPP4 expression on circulating immune cells. Peripheral blood mononuclear cells (PBMCs) were isolated from healthy volunteers and CD14 + CD16+ monocyte, CD16 + CD14-granulocyte, CD19+ B lymphocyte, CD3 + CD4+ T lymphocyte and CD3 + CD4- T lymphocyte were gated for the detection of DPP4 using an imaging flow cytometer. B & C, White blood cells (WBC) and plasma were isolated from wild-type (WT) and DPP4^−/− mice for the detection of DPP4 enzymatic activity. WBC and plasma DPP4 activity (B) and blood DPP4 activity composition in the WT mouse (C) are shown. D, Irradiated DPP4^−/− mice were transplanted with WT or DPP4^−/− bone marrow cells. Plasma were then isolated for the detection of DPP4 enzymatic activity after 12 weeks. E & F, WT C57BL/6 mice (n = 5–6/group) were treated with 5 mg/kg body weight (BW)/day linagliptin (DPP4i) in drinking water for 4 weeks and then subjected to flow cytometric detection of DPP4 expression. Representative dot plot (E) and statistical analyses (F; upper panel: % of DPP4+ macrophages; lower panel: DPP4mean fluorescence intensity) are shown. *, p < .05.