Thrombosis in Tregs-Induced Thrombocithopenia in Patients with Myelofibrosis

Background: High levels of anti-PF4 antibody are associated with increased thrombosis risk. In myelofibrosis (MF) there is T-regulatory cells (Tregs)-mediated autoimmunity.

Aim: We investigated Tregs, anti-PF4 antibodies, and platelet and coagulation function in patients with MF and thrombosis.

Methods: We enrolled 30 patients with WHO-defined MF (20 men, 10 women; mean age 50±5 years) without cardiovascular risk factors or history of thrombosis having poplitea deep vein thrombosis (20/30) and pulmonary embolism (10/30) revealed with lower-limb ultrasonography and computed tomography (CT) angiography. 30 healthy subjects age- and sex-matched served as controls. All patients were evaluated for Tregs, anti-PF4-antibodies, platelets, platelet function assay (PFA-100) and Thromboelastometry assay. Tregs were measured by flow cytometry, anti-PF4 antibodies using a enzyme-linked immunosorbent assays (ELISA), platelets by automated analyzer, platelet function assay by PFA-100 using Collagen/ADP (CT-ADP) and Collagen/Epinephrine (CT-EPI) cartridges and Thromboelastometry by ROTEM using Clotting Time (CT), Clotting Formation Time (CFT), Maximum Clot Firmness (MCF), and clot lysis at 30 minutes (LY-30). Results: All patients had low Tregs (1,2±0,2% vs 4±1%, thrombocytopenia (50±10x109/L vs 200±10x109/L), shorter C/ADP and C/EPI (C/ADP, n.v. 68-121 s (35±5s vs 90±10 s) and C/EPI n.v. 84-160 s (45±5 s vs 110±20 s) and shorter CT (CT, unit: s. n.v. INTEM 100-240 s, EXTEM 38-79 s) (INTEM 55±20 s vs 190±10 s, EXTEM 25±5 s vs 48±8 s), shorter CFT (CFT, unit: s, n.v. INTEM 30-160 s, EXTEM 34-159 s (INTEM 12±8 s vs 110±20 s, EXTEM 15±10 s vs 120±10 s), longer MCF (MCF, unit: mm, n.v. INTEM and EXTEM 50-72 mm (INTEM 125±5 mm vs 55±5 mm, EXTEM 110±5 mm vs 65±5 mm), and lower LY-30 (LY-30, %: v.n. INTEM and EXTEM 15% (INTEM 0.8% vs 15%, EXTEM 0.7% vs 15%).

Conclusions: These results skow that the anti-PF4/Tregs antibodies may be involved in the thrombogenesis of patients with MF.

No relevant conflicts of interest to declare.