Antiplatelet antibodies in WASP(−) mice correlate with evidence of increased in vivo platelet consumption

Abstract

Objective: To study the role of anti-platelet antibodies in the thrombocytopenia of murine WAS. Methods: A flow cytometric method was developed for detection of serum anti-platelet antibodies via their binding to intact target platelets lacking surface antibodies. Platelets were labeled with CMFDA in order to track their clearance from the circulation. WASP(−)μMT(−/−) mice were generated by standard breeding methods. Results: Serum anti-platelet 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, 5-10% of them show a more severe thrombocytopenia associated with increased reticulated platelets, suggesting the presence of clearance-inducing antiplatelet antibodies (CIAA). In support of that inference, 90% of the latter mice show detectable serum antiplatelet antibodies. The antibodies are primarily IgG, and are also detected in over 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 which largely requires WASP deficiency in trans, and an antibody dependent mechanism which does not. Both an increased incidence of antiplatelet antibodies and an increased susceptibility to their effects contribute to antibody dependent clearance of WASP(−) platelets.

Wiskott–Aldrich syndrome: diagnosis, current management, and emerging treatments

“…Megakaryocyte numbers are typically normal in patients with WAS; however, platelet formation is abnormal 29. Moreover, platelet destruction in association with antiplatelet antibodies may be a contributing factor in the maintenance of thrombocytopenia 30. Perturbations in platelet function are also notable, and may result in increased risk of bleeding and diminished platelet survival 29.…”

Increased uptake by splenic red pulp macrophages contributes to rapid platelet turnover in WASP(–) mice

“…There is evidence that increased platelet consumption also contributes to the thrombocytopenia of clinical and murine WAS[9, 10]. Using a numerical analysis model, we have shown that both cis (platelet intrinsic) and trans (recipient dependent) features of WASP deficiency contribute to the rapid clearance of murine WASP(−) platelet from the circulation[11].…”

Pathogenesis and management of inherited thrombocytopenias: rationale for the use of thrombopoietin-receptor agonists

“…Studies on WASp-null mice and WAS patients demonstrated that defective platelets are cleared at a faster rate by macrophages [70][71][72]. Anti-platelet autoantibodies could contribute to this process [73]. Investigations on murine models also suggested an ineffective platelet production deriving from premature PPF within BM and impaired SDF1-driven migration of Mks [74].…”