Scavenger receptor (immunology)

Scavenger receptors are receptors on macrophages and other cells that bind to numerous ligands, such as bacterial cell-wall components, and remove them from the blood. The Kupffer cells in the liver are particularly rich in scavenger receptors. Includes SR-A I, SR-A II, and MARCO.

Scavenger receptors are thought to participate in the removal of many foreign substances and waste materials in the living body by extensive ligand specificity and a variety of receptor molecules.

In atherosclerotic lesions, macrophages that express scavenger receptors on their plasma membrane take up the oxidized LDL deposited in the blood vessel wall aggressively, and develop into foam cells. Likewise, they secrete various inflammatory cytokines and accelerate the development of atherosclerosis.

Scavenger receptors are categorized into classes A, B, C according to their structural characteristics.

Scavenger receptors type 1 (SR-A1) and 2 (SR-A2) are trimers with a molecular weight of about 220-250 kDa (the molecular weight of monomeric protein is about 80 kDa). They preferentially bind modified LDL, either acylated (acLDL) or oxidized (oxLDL). They have a collagen-like domain, which is essential for ligand binding.

Members include:

CD36 and scavenger receptor class BI (SR-BI) are identified as oxidized LDL receptors and classified into class B. Both proteins have two transmembrane domains, and they are concentrated in a specific plasma membrane microdomain, the caveolae.

Members include:

Some receptors that can bind to oxidized LDL have been discovered.

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