FCRL4 and hepatitis B virus infection: In addition, B cells associated with dysfunction and failure also express a series of coinhibitory receptors, including Fc receptor like 4 (FcRL4), PD-1, and PD-L1 [90], although there was no significant difference between the low-level HBsAg group and the high-level HBsAg group, B cell function in hepatitis B patients with low levels of HBsAg may still be impaired, resulting in immune tolerance [86].