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CD Markers


Reviewers: Nat Pernick, M.D., PathologyOutlines.com (see Reviewers page)
Revised: 24 December 2010, last major update December 2010
Copyright: (c) 2002-2010, PathologyOutlines.com, Inc.


● Platelet receptor that mediates adhesion to subendothelial tissue after endothelial damage


● Also called very late antigen (VLA) alpha 2 chain
● Called GP Ia/IIa receptor (integrin alpha2beta1) on platelets


● Receptor for laminin, collagen, fibronectin, E-cadherin
● Responsible for platelet adhesion to subendothelial tissue; after endothelial damage, circulating platelets via platelet surface GP Ib-IX-V complex contact subendothelial vWF bound to collagen; this initial contact slows down the platelets, allowing platelet CD49b to bind to endothelial collagen; this stops the platelets, and contributes to their activation and aggregation (Blood 2005;105:1986)
● CD49b mediates disassembly of actin cytoskeleton stress fibers and focal adhesions, leading to block of endothelial cell migration and angiogenesis (J Cell Biol 2004;166:97)
● May be a immunodominant minor histocompatibility antigen (Blood 1998;92:2169)


Platelet receptors

Clinical features

● Associated with neonatal alloimmune thrombocytopenia (CD49b is BRa, Vox Sang 1988;54:101)
● Elevated numbers of peripheral blood CD18(high) CD49b+ T cells are associated with severe uncontrolled asthma (Int Arch Allergy Immunol 2006;140:139)
● CD49b C807T polymorphism is associated with high density of alpha2beta1 receptor on platelets (Arterioscler Thromb Vasc Biol 2005;25:1756); severe retinopathy in patients with diabetes >25 years (Thromb Haemost 2003;89:142); and ischemic strokes in young monozygotic twins (Blood Coagul Fibrinolysis 2003;14:83)

Uses for pathologists

● No significant clinical use by pathologists

Positive stains - normal

● Platelets, activated B & T cells, monocytes, megakaryocytes, NK cells (most)


Platelet adhesion and aggregation

Additional references

MIM 192974

End of CD Markers > CD49b

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