Background Activated T cells express RANKL and have been considered to pomote osteoclast (OC) differentiation. Alternatively, activated T cells were suggested to suppress OC differentiation via the production of IL-4 and IL-10. Additionally, in a mouse model, activated T cells were reported to drive monocytes to differentiate into dendritic cells (DCs) through GM-CSF production. 1)
Objectives In this study, we investigated effects of CD4+ T cells or CD8+ T cells with or without IL-2 on the induction of OC from human monocytes.
Methods Monocytes, CD4+ T cells, and CD8+ T cells were prepared from PBMC of healthy volunteers. After incubation of monocytes with RANKL (50 ng/ml) and M-CSF (20 ng/ml) for 14 days, OC differentiation was evaluated by the TRAP staining. Additionally, we added CD4+T cells or CD8+T cells with or without IL-2 (20U/ml) at the initiation of the culture.
Results Apparent OCs were induced from human monocytes by the culture with RANKL and M-CSF. The addition of CD8+ T cells facilitated the OC differentiation. Conversely, the addition of CD4+ T cells with IL-2 remarkably inhibited the OC differentiation, with preferential induction of DCs.
Conclusions CD8+ T cells seem to facilitate OC differentiation from monocytes. Alternatively, irrespective of the presence of RANKL and M-CSF, CD4+ T cells with IL-2 facilitate DC differentiation, thereby resulting in drastic inhibition of OC differentiation.
Miyamoto T, Ohneda O, Arai F, Iwamoto K, Okada S, Takagi K, et al. Bifurcation of osteoclasts and dendritic cells from common progenitors. Blood. 2001,15;98(8):2544-54.
Disclosure of Interest None declared