What are Kupffer cells and what is their role in liver function?

• A. Cholangiocytes lining bile ducts.
• B. Endothelial cells lining sinusoids.
• C. Resident macrophages in hepatic sinusoids; they phagocytose pathogens and debris.
• D. Hepatocytes that secrete bile.

Answer: (C)

Kupffer cells are specialized macrophages that permanently reside in the hepatic sinusoids, forming part of the liver’s scavenging system. Their main job is to monitor blood from the gut for pathogens and debris, phagocytosing bacteria, endotoxins, and worn-out cells as it passes through the sinusoids. This puts a first line of defense against infection in the portal circulation and helps keep the liver—and the rest of the body—clean of harmful material. They also release signaling molecules to modulate inflammation and can present antigens to help coordinate the immune response. This role is distinct from cholangiocytes that line bile ducts, sinusoidal endothelial cells that line the vessels, and hepatocytes that produce bile and carry out metabolic functions.