Figure 5. Treg cells suppress osteoclast differentiation in vitro. (A–B) Treg cells suppressed osteoclast differentiation mediated by RANKL. Mouse bone marrow cells (BMCs) were cultured as described with RANKL in the absence or presence of Treg cells. The cultured cells were subject to TRAP staining. TRAP-positive multinucleated (> 3 nuclei) cells were counted. (A) Results are reported as the number of osteoclast (OC)-like cells per coverslip ± SD n = 5, *p < 0.01. (B) Representative images showed osteoclast (OC)-like cells. (C and D) Treg cells suppressed osteoclast differentiation mediated by M-CSF and CD8⁺ T cells. Mouse bone marrow cells were cultured as described with M-CSF (C) or activated CD8⁺ T cells (D) in the presence of different concentrations of Treg cells. Results are reported as the number of osteoclast (OC)-like cells per coverslip ± SD n = 6, *p < 0.01.