Macrosialin

Macrosialin, also known as CD68, is a glycoprotein that is highly expressed on the surface of macrophages and other cells of the mononuclear phagocyte system. It is a member of the lysosome-associated membrane glycoprotein (LAMP) family and plays a role in the immune system by mediating the uptake of lipoproteins and phagocytosis of cellular debris.

Structure

Macrosialin is a type I transmembrane protein with a large extracellular domain rich in sialic acid residues, which contributes to its name. The protein is encoded by the CD68 gene located on chromosome 17 in humans. The extracellular domain contains several glycosylation sites, which are important for its function and stability.

Function

Macrosialin is primarily involved in the endocytosis and phagocytosis of pathogens, apoptotic cells, and cellular debris. It is also implicated in the antigen presentation process, where it helps in the processing and presentation of antigens to T cells.

Expression

CD68 is predominantly expressed in macrophages, but it is also found in other cells of the immune system, such as dendritic cells and monocytes. Its expression is often used as a marker for identifying macrophages in histological studies.

Clinical significance

The expression of CD68 is used as a diagnostic marker in various pathological conditions, including inflammatory diseases, atherosclerosis, and certain types of cancer. Elevated levels of CD68-positive macrophages are often associated with chronic inflammation and tumor progression.

See also

• Macrophage
• Immune system
• Phagocytosis
• Antigen presentation

External links

• CD68 gene information at NCBI
• CD68 protein information at UniProt