Novel clearance mechanisms of platelets.
OBJECTIVE
Blood platelets are involved in primary and secondary hemostasis and thus maintain the integrity of the vasculature. They circulate with an average lifespan of 5-9 days in humans. Thus, the body must generate and clear platelets daily to maintain normal physiological blood platelet counts. Known platelet clearance mechanisms include antibody-mediated clearance by spleen macrophages, as in immune thrombocytopenia, and platelet consumption due to massive blood loss.


RESULTS
New concepts in the clearance mechanisms of platelets have recently emerged. New evidence shows that platelets desialyted due to chilling or sepsis are cleared in the liver by macrophages, that is Kupffer cells, as well as hepatocytes, through lectin-mediated recognition of platelet glycans. On the contrary, platelet-associated antibodies normalize the clearance of platelets in a mouse model for Wiskott-Aldrich syndrome.


CONCLUSIONS
The goal of this review is to summarize the latest findings in platelet clearance mechanisms with a focus on lectin-mediated recognition of platelet glycans. Transfusion medicine and treatments of hematopoietic disorders associated with severe thrombocytopenia may benefit from a better understanding of these mechanisms.
Grozovsky
Renata
R
Division of Translational Medicine, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts 02115, USA.
Hoffmeister
Karin M
KM
Falet
Hervé
H
D000818:Animals; D001792:Blood Platelets / Q000166:cytology / Q000502:physiology*; D006487:Hemostasis; D006801:Humans; D051379:Mice; D010976:Platelet Count; D017713:Platelet Transfusion; D013921:Thrombocytopenia / Q000097:blood; D014923:Wiskott-Aldrich Syndrome / Q000097:blood