A raised expression of matrix metalloproteinase MMP-9 (gelatinase-B) [77] is also found in scarring trachoma; this is a metalloproteinase that is not only induced by NK cells but also induced and regulated via the Th1 cytokine, IFN-γ. The expression of conjunctival MMP-9 has been found to be markedly raised in children with active trachoma [78]. Here, IFNG is linked to inclusion conjunctivitis.