IL6 and COVID-19: Elevated levels of IL-6 and TGF-β have been correlated with severe lung inflammation and fibrosis, as well as dysregulation of the kynurenine pathway (KP), a TRP metabolic pathway consistently disturbed in COVID-19 patients (Chatterjee and Maparu, 2025; Hu et al., 2021; Moura-Alves et al., 2014; Ragab et al., 2020; Thomas et al., 2020).