Kupffer cells are a specialized form of immune cells that exist only within the liver. They are one of several kinds of macrophages, a type of white blood cell, that help the body maintain health by destroying bacteria, old blood cells and other foreign substances that occur in the blood stream because of illness, injury or body malfunction or simply through natural aging of the various body cells. These cells develop within the bone marrow, then migrate to the liver, where they complete their development into cells specially designed to protect the liver.
These specialized cells are considered part of the reticuloendothelial system, a part of the immune system. This subdivision of the overall human immune system consists not only of the Kupffer cells, but also of immune cells located in the reticular connective tissue. Reticular connective tissue is specialized tissue that supports the lymph nodes, the spleen and the red bone marrow. It also helps support adipose tissue, or fat cells. All of these elements contribute to the complex network of cells and organs that constitute the human immune system.
Originally discovered in 1876 by Karl Wilhelm von Kupffer, these cells originally were believed to originate within the liver and to constitute part of the lining of the liver's blood vessels. Additional research and observation led another scientist, Tadeusz Browicz, to realize that they were macrophages that originated not in the liver, but in the bone marrow. He made this discovery in 1898, and because of his role in their discovery and function, they are sometimes also called Browicz-Kupffer cells. Since then, scientists have discovered many of their functions, including their role in recycling dead blood cells and helping the liver respond to toxic substances in the blood stream.
As part of their normal immune function, Kupffer cells also help repair injury to the liver. They have a role in the development of cirrhosis of the liver, a serious disease characterized by scarring and excess fibrous tissue in the organ, most often caused by excessive alcohol consumption. Some triggers, including carcinogenic agents, can cause the cells to initiate production of collagen, a connective tissue, within the liver. Too much of this tissue, as well as excessive scarring in the liver, eventually renders the liver unable to perform its normal function. It also makes it impossible for the liver to regenerate itself as it does under normal circumstances.