CD Markers
CD42b

Author: Nat Pernick M.D. (see Authors page)

Revised: 7 January 2016, last major update December 2010

Copyright: (c) 2002-2016, PathologyOutlines.com, Inc.

PubMed Search: CD42b

Related: CD42a, CD42c, CD42d

Cite this page: CD42b. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/cdmarkerscd42b.html. Accessed December 4th, 2016.
Definition / General
  • CD42a-d complex is receptor for von Willebrand factor and thrombin
  • Also called platelet GPIb alpha, glycoprotein Ib-alpha
  • Mutations are associated with Bernard-Soulier syndrome (giant platelet syndrome, OMIM #231200, Int J Hematol 2002;76:319), a bleeding disorder with thrombocytopenia, prolonged bleeding time and giant platelets
  • CD42b mutations also cause platelet type von Willebrand disease, which is known as pseudo-von Willebrand disease (OMIM #177820)
  • Reduced levels are associated with bleeding disorders in AML patients (Saudi Med J 2005;26:1095)
  • Aspirin induces shedding of CD42d and CD42b from platelets (J Biol Chem 2005;280:39716)
  • Various snake venoms induce platelet aggregation via CD42b, including TVMA (Toxicon 2004;44:649, but see Xenotransplantation 2004;11:203-inhibits platelet aggregation), alboluxin (Thromb Haemost 2002;87:692) and bilinexin (Thromb Haemost 2001;86:1277)
  • CD42b physiology is part of bacterial virulence factors:
    • Streptococcus sanguis, an oral bacteria causing infective endocarditis, adheres to platelets and platelet-fibrin vegetations via CD42b (Br J Haematol 2005;129:101)
    • Some strains of H. pylori induce platelet activation mediated by H. pylori-bound vWF interacting with CD42b, which may promote peptic ulcer disease and H. pylori-associated cardiovascular disease (Gastroenterology 2003;124:1846)
Diagrams / Tables

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CD42a-d complex

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Interactions

Pathophysiology
  • CD42a-d complex (also called glycoprotein Ib-IX-V receptor) is the surface platelet receptor for von Willebrand factor on endothelium (particularly CD42b)
  • Endothelial damage exposes vWF, which binds to platelets very quickly despite high shear pressures; this leads to platelet activation, then a change in the platelet GpIIb-IIIa receptor, which allows binding to surface bound fibrinogen and free fibrinogen; this leads to platelet crosslinking and aggregation
  • Platelet activation apparently involves disruption of the macromolecular complex of GP-Ib with the platelet glycoprotein IX (GP-IX) and dissociation of GP-Ib from the actin-binding protein
  • GPIb alpha (CD42b) and GPIb beta (CD42c) form main part of VWF receptor
  • CD42b also binds to thrombospondin-1, a glycoprotein in arteriosclerotic plaques, causing thrombus formation independent of von Willebrand factor (FASEB J 2003;17:1490)
  • Platelet receptors are important in understanding thrombus formation (Haematologica 2009;94:700)
Case Reports
Uses by Pathologists
  • Marker of megakaryocytes and platelets
  • Diagnosis of AML-M7; distinguish AML-M7 (CD42b+) from acute myelosis with myelofibrosis (usually CD42b neg, Mod Pathol 2005;18:603)
Micro Images

Nature images:

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Bone marrow aspirate

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Acute panmyelosis

Positive Staining - Normal
  • Platelets, megakaryocytes and megakaryoblasts
Positive Staining - Disease
  • Blasts in transient myeloproliferative disorder
Flow Cytometry Images

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Reduced CD42b

Additional References