The results demonstrate that the level of mRNA expression of IL-6, IL-8, IL-10, COX-2, IL-1β, IL-18, and TNF-α were significantly upregulated in peripheral blood monocytes following infection with H. parasuis for 3 or 6 h (p < 0.01) (Figures 3I–O). Here, CXCL8 is linked to infection.