C4A and colitis: C4 significantly inhibits the production of proinflammatory cytokines (e.g., IL-6, TNF-α and IFN-γ) and chemokines (e.g., CCL3, CCL4, CXCL1 and IL-8) secreted by neutrophils in the intestines of patients with colitis to reduce intestinal inflammation, and C4 inhibits the secretion of proinflammatory cytokines in an HCDAC-dependent manner (99).