IFNG and infection: During infection and upregulation of IFN-γ, Ct trpBA expression is induced, but in the absence of indole, the β subunit catalyzes the deamination of l-serine to produce pyruvate and ammonia (38), an antimicrobial agent that can also induce apoptosis of epithelial cells, especially under higher pH levels (39), similar to those found on the ocular surface of healthy patients (40).