Antiplatelet antibodies in WASP(−) mice correlate with evidence of increased in vivo platelet consumption
Received 10 July 2009; received in revised form 10 August 2009; accepted 27 August 2009. published online 04 September 2009.
Objective
To study the role of antiplatelet antibodies in the thrombocytopenia of murine Wiskott-Aldrich syndrome (WAS).
Materials and Methods
A flow cytometric method was developed for detection of serum antiplatelet antibodies via their binding to intact target platelets lacking surface antibodies. Platelets were labeled with 5-chloromethylfluorescein diacetate (CMFDA) in order to track their clearance from the circulation. WASP(−)μMT(−/−) mice were generated by standard breeding methods.
Results
Serum antiplatelet antibodies were detected in approximately 40% of WASP(−) males. The mean level of reticulated platelets is significantly increased in these antibody(+) males. While WASP(−) males show an approximately 50% reduction in platelet counts, 5% to 10% show a more severe thrombocytopenia associated with increased reticulated platelets, suggesting the presence of clearance-inducing antiplatelet antibodies. In support of that inference, 90% of the latter mice show detectable serum antiplatelet antibodies. The antibodies are primarily immunoglobulin G, and are also detected in >30% of CD47(−/−) males. WASP(−)μMT(−/−) males, which demonstrate no serum- or platelet-associated antibodies, show a degree of thrombocytopenia similar to that of WASP(−) males. Their platelet clearance rates remain accelerated—more so in WASP(−)μMT(−/−) than WASP(+)μMT(−/−) recipients.
Conclusions
These findings suggest that platelet WASP deficiency results in an increase in platelet clearance rates by two mechanisms: an antibody-independent mechanism that largely requires WASP deficiency in trans, and an antibody-dependent mechanism that does not. Both an increased incidence of antiplatelet antibodies and an increased susceptibility to their effects contribute to antibody-dependent clearance of WASP(−) platelets.
aDepartment of Pathology and Laboratory Medicine, University of Tennessee Health Sciences Center, Memphis, Tenn., USA
bDepartment of Pathology and Laboratory Medicine, Memphis Veterans Administration Medical Center, Memphis, Tenn., USA
cSeattle Children's Hospital Research Institute, Seattle, Wash., USA
dDepartment's of Pediatrics and Immunology, University of Washington School of Medicine, Seattle, Wash., USA
eDepartment of Preventive Medicine, University of Tennessee Health Sciences Center, Memphis, Tenn., USA
Offprint requests to: Ted S. Strom, M.D., Ph.D., Department of Pathology and Laboratory Medicine, Memphis VA Medical Center, 1030 Jefferson Avenue, Memphis, TN 38104
ABSTRACT