Abstract
(1) Background: Aluminum oxide (Al2O3) ceramic is one of the materials used for artificial joints, and it has been known that their fine particles (FPs) are provided by the wear of the ceramic. Al2O3 FPs have been shown to induce macrophage activation in vitro; however, the inflammatory effect in vivo has not been studied. (2) Methods: We examined the in vivo effect of Al2O3 FPs on the innate and adaptive immune cells in the mice. (3) Results: Al2O3 FPs promoted the activation of spleen macrophages; however, conventional dendritic cells (cDCs), plasmacytoid DCs (pDCs), and natural killer (NK) cells were not activated. In addition, increases in the CD4 and CD8 T cells was induced in the spleens of the mice treated with Al2O3 FPs, which differentiated into interferon-gamma (IFN-γ)-producing helper T1 (Th1) and cytotoxic T1 (Tc1) cells. Finally, the injection of Al2O3 FPs exacerbated dextran sulfate sodium (DSS)-induced inflammation in the colon, mediated by activated and increased number of CD4 and CD8 T cells. (4) Conclusions: These data demonstrate that FPs of Al2O3 ceramic may contribute to the exacerbation of inflammatory diseases in the patients.