Figure 1.

Potential regulatory mechanisms activated by TCZ therapy in COVID-19 patients. COVID-19 is associated to a CRS referred as “cytokine storm” (A), whose reduction at lung level (the main target organ of SARS-CoV2 viral infection) may be achieved by TCZ therapy inhibiting IL-6 proinflammatory effect (B). Neutralization of IL-6 biological activity by TCZ potentiates IDO1-mediated conversion of the amino acid Trp into its catabolite Kyn (C). Increased level of circulating Kyn contributes to control pulmonary hypertension and inflammation, and to promote immunoregulation in COVID-19 patients.