Fig. (3) TNF-α secretion from monocytes/macrophages (n=3-4) and osteoclasts (n=8), challenged with particles and ions with or without LPS for 24 hours. PBMCs are obtained from human whole blood, monocytes/macrophages are isolated from PBMCs, and challenged with metal particles or ions, with and without LPS, for 24 hours. To form osteoclasts, monocytes/macrophages are cultured with M-CSF (50 ng/ml) and RANKL (100 ng/ml) for 6-7 days, and challenged with metal particles or ions, with and without LPS, for 24 hours. 24 hours later, TNF-α cytokine secretion is assessed in supernatants of each condition. (A) Comparison between the cytokine secretion of unprimed (no LPS) monocytes/macrophages and osteoclasts (asteriks indicate statistical significance of monocyte vs osteoclasts comparison for each challenge condition at p = 0.0009), (B) Comparison between the cytokine secretion of primed/co-challenged monocytes/macrophages and osteoclasts (asteriks indicate statistical significance of monocyte vs osteoclasts comparison for each challenge condition at p < 0.0001), (C) Comparison of TNF-α cytokine secretion from primed/co-challenged and unprimed monocytes/macrophages, and (D) Comparison of TNF-α cytokine secretion from primed/co-challenged and unprimed osteoclasts. Note: Ti = Titanium, Co = Cobalt, PMMA = polymethylmethacrylate (bone cement), Ng= Nigericin, Alum=Alum vacine adjuvant; * = p<0.05 comparing corresponding values between monocytes/macrophages and osteoclasts, ** = p < 0.05 between the two highlighted conditions.