In a patient with acute mixed hepatocellular/cholestatic hepatitis after the first dose of BNT162b2 mRNA vaccine and severe autoimmune hepatitis (AIH) after booster, IMC analysis of liver tissue collected 26 days post-boost revealed a dominant infiltration of activated cytotoxic CD8+ T cells (GZMB+) broadly distributed throughout the liver parenchyma [86]. The gene discussed is CD8A; the disease is autoimmune hepatitis.