CD88

CD88, also known as the complement receptor 1 (CR1) or cluster of differentiation 88, is a protein that plays a crucial role in the immune system. It is primarily found on the surface of various blood cells, including erythrocytes, neutrophils, monocytes, macrophages, and some lymphocytes. The CD88 protein is a type I transmembrane glycoprotein belonging to the regulators of complement activation (RCA) gene cluster.

The main function of CD88 is to bind to complement fragments, specifically C3b and C4b. These fragments are generated during the activation of the complement system, a cascade of proteins that helps clear pathogens and damaged cells. By binding to these fragments, CD88 acts as a cofactor for the enzymatic degradation of C3b and C4b. This regulatory function is essential for preventing excessive complement activation, which could otherwise lead to tissue damage.

Furthermore, CD88 is involved in the clearance of immune complexes, which are aggregates of antigens and antibodies. By binding to immune complexes via C3b, CD88 facilitates their transport to the liver and spleen for removal. This process helps prevent the deposition of immune complexes in tissues, which can trigger inflammatory responses. Research has also suggested roles for CD88 in other cellular processes, including cell adhesion and proliferation. Its expression levels can vary depending on cell type and activation state, and alterations in CD88 are sometimes associated with certain autoimmune diseases.