Although we could not analyze the effect of gut microbiota on TLR4 signaling in macrophages, we found that GF mice have a significant reduction of pro-inflammatory cytokines in macrophages and aorta, suggesting that the absence of gut microbiota resulted in the reduction of inflammatory cytokines and chemokines in systemic circulation, which might result in the reduction of atherosclerosis. The gene discussed is TLR4; the disease is atherosclerosis.