Abstract Number: VPB1223
Meeting: ISTH 2022 Congress
Background: Immune thrombocytopenia (ITP) is a bleeding disorder characterized by a low platelet count. T cells have been implicated in the pathogenesis of ITP, but evidence of platelet-specific CD8+ T cells is lacking.
Aims: Detect platelet-specific CD8+ T cells in ITP patients. Characterize CD8+ T cell regulation and activity in ITP.
Methods: Peripheral blood mononuclear cells from ITP patients (n=11) and healthy individuals (n=10) were labelled with carboxyfluorescein succinimidyl ester (CFSE) to detect platelet-specific T cell proliferation in response to platelet autoantigens. CD8+ T cell proliferation was assessed by flow cytometry after 9 days of stimulation with GP IIbIIIa or Ibα. Anti-GP IIbIIIa and anti-GP IbIX were measured with the direct antigen capture assay. Plasma TGF-β, IL-6, GrA, GrB, and sCD137 were assessed by multiplex (Eve Technologies) in ITP patients, healthy individuals, and non-ITP patients (n=5). P values < 0.05 were considered significant. Informed consent was obtained, and the study was approved by the Hamilton Integrated Research Ethics Board.
Results: After stimulation with GP IIbIIIa, 5 of 11 ITP patients and 6 of 10 healthy individuals showed a CD8+ T cell proliferative response. After stimulation with GP Ibα, 9 of 11 ITP patients and 7 of 10 healthy individuals showed a CD8+ T cell proliferative response (Figure 1). Platelet counts and autoantibody levels were comparable in patients with or without platelet-specific T cells. Plasma TGF-β was significantly lower in ITP patients, while IL-6, GrA, GrB, and sCD137 were significantly elevated in ITP patients compared to healthy individuals and non-ITP patients (Figure 2).
Conclusion(s): Platelet-specific CD8+ T cells can be found in ITP and in healthy individuals, and CD8+ T cell activity is dysregulated in ITP patients. Platelet-specific CD8+ T cells should be isolated are characterized for their ability to promote platelet destruction and underproduction in future investigations.
To cite this abstract in AMA style:Vrbensky J, Nazy I, Kelton J, Larché M, Clare R, Bhakta H, Roussakis M, Rybenchuk V, Arnold D. Platelet-Specific CD8+ T Cells in Patients with Immune Thrombocytopenia [abstract]. https://abstracts.isth.org/abstract/platelet-specific-cd8-t-cells-in-patients-with-immune-thrombocytopenia/. Accessed October 1, 2023.
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