STAT3 and dry eye syndrome: We also analyzed the expression and activation of the ERK1/2 MAPK signaling pathway reported to be expressed and phosphorylated in the cornea in response to inflammation associated with experimentally induced dry eye.58 Unlike STAT3, we found that ERK1/2 was constitutively phosphorylated in the corneas of UI mice, without significant changes upon infection, regardless of treatment (Figs. 5G–H).