Fig. 2: Accumulation of 4-1BB and 4-1BBL in the bone marrow microenvironment and upregulation of 4-1BB in BMSCs from aged mice.

a 4-1BBL levels in bone marrow from 6- and 18-month-old mice were determined by ELISA. b 4-1BB levels in bone marrow from 6- and 18-month-old mice. c 4-1BB and 4-1BBL expression on hematopoietic stem cells (HSCs), myeloid progenitors (MPs), bone marrow stromal cells (BMSCs), and bone marrow dendritic cells (BM-DCs) by flow cytometry. d 4-1BB levels in 24-h in vitro culture supernatants of BMSCs from 6- and 18-month-old mice. e 4-1BB protein expression in BMSCs from 6- and 18-month-old mice was determined by western blot. β-Actin was used as an internal control for western blotting. All the data were obtained from three independent experiments. Data are shown as the means ± SEMs. *p < 0.05, **p < 0.01, ***p < 0.001, 18 mo vs. 6 mo.