CD4 and hepatitis B virus infection: The MFI of BTLA expression on CD4+ T cells exhibited positive correlations with various disease severity indicators, including Child-Pugh scores21, model for end-stage liver disease (MELD) scores22, CLIF-Sequential Organ Failure Assessment (SOFA)20, CLIF-C ACLFs23, and Chinese Group on the Study of Severe Hepatitis B (COSSH)-ACLFs24 (Fig. 1e; Supplementary Fig. 1c).