IL6 and keratitis: LPS, a component of the cell wall of Gram-negative bacteria, can resist the killing effects of the host’s complement and activate the TLR 4 pathway to produce proinflammatory cytokines such as IL-6 and TNF-α, which recruit neutrophils for corneal infiltration, and lymphangiogenic factors, including VEGF-C and VEGFR-3, which are produced in large numbers in late keratitis.