CD33 and viral hepatitis: Several studies provide evidence of a possible interaction between CD33 and viral hepatitis: specifically, hepatitis B virus (HBV) activation of CD33 on myeloid cells may facilitate immune evasion,9 and hepatitis C virus (HCV) increases CD33+ myeloid-derived suppressor cells (MDSCs), impairing T-cell function.10,11 This indicates a complex relationship between CD33, viral hepatitis and immune regulation.