HBsAg uptake by macrophages in vitro: an immunofluorescence study

Kupffer cells interact with hepatitis B surface antigen in vivo and in vitro, leading to proinflammatory cytokine production and natural killer cell function

BACKGROUND

Based on their localization, Kupffer cells (KCs) likely interact with hepatitis B virus (HBV). However, the role of KCs in inducing immunity toward HBV is poorly understood. Therefore, the interaction of hepatitis B surface antigen (HBsAg) and KCs, and possible functional consequences, were assessed.

METHODS

KCs in liver tissue from patients with chronic HBV were analyzed for presence of HBsAg and their phenotype, and compared with KCs in control liver tissue. Liver graft perfusate-derived KCs and in vitro-generated monocyte-derived macrophages were investigated for functional interaction with patient-derived HBsAg.

RESULTS

Intrahepatic KCs were HBsAg positive and more activated than those from control livers. KCs internalized HBsAg in vitro, which did not change their phenotype, but strongly induced proinflammatory cytokine production. Additionally, monocyte-derived macrophages also interacted with HBsAg, leading to activation and cytokine production. Furthermore, HBsAg-exposed macrophages and KC activated natural killer (NK) cells, resulting in increased CD69 expression and interferon-γ production.

CONCLUSIONS

KCs directly interact with HBsAg in vivo and in vitro. HBsAg-induced cytokine production by KCs and monocyte-derived macrophages and subsequent NK cell activation may be an early event in viral containment and may support induction of HBV-specific immunity upon HBV infection, but may also contribute to liver pathology.

Hepatitis B surface antigen (HBSAg) in peritoneal fluid of HBSAg carriers undergoing peritoneal dialysis

Samples of ascitic fluid and outflow dialysate were collected from HBSAg carriers undergoing peritoneal dialysis and tested for HBSAg by solid-phase radioimmunoassay. The surface antigen was detected in every sample from HBSAg carriers. This finding was not dependent upon the presence of occult blood in the sample. Surface antigen particles and possibly Dane particles were also observed in HBSAg-positive samples by immunoelectron microscopy. These results identify the outflow dialysate of HBSAg carriers undergoing peritoneal dialysis as a potential source of hepatitis B virus transmission.