MMP9 and keratoconus: Moreover, systemic inflammatory markers such as elevated toll-like receptor- (TLR-) 2 and 4 expression in neutrophils and monocytes and higher serum levels of interleukin- (IL-) 1β, IL-6, tumor necrosis factor- (TNF-) α, MMP-9, and NF-κB were found in KC patients [19].