Background: Antiphospholipid syndrome (APS) may occur as a primary condition or secondary to an underlying disease, most often Systemic Lupus Erythematosus (SLE). Platelets are activated in APS, but their pathogenic role, particularly in pregnancy-associated thrombosis or placental complications, is unclear. Also, while it is known that platelet-leucocyte aggregates (PLAs) are increased in APS, their role in pregnancy and SLE/APS is unknown.

Aims: To demonstrate the procoagulant potential of platelet and leukocytes in the prothrombotic state of SLE/APS.

Methods: We utilised a high-resolution dynamic imaging approach to examine platelet and neutrophil membranes, and their interactions in platelet-rich-plasma plus from two pregnant patients with SLE and secondary APS (week 20-22) and gestational age-matched healthy pregnant controls (PC). Both SLE/APS patients were maintained on therapeutic doses/regimen of low-molecular-weight heparin (LMWH) and acetylsalicylic acid (ASA) (162 mg/day), hydroxychloroquine and prednisone; and one received azathioprine and rituximab in addition. Platelet-rich-plasma plus (PRP+) was reconstituted to contain leucocytes by centrifuging whole blood at 180g for 17 minutes, followed by careful extraction of the whole supernatant, which included the upper plasma fraction (PRP) and the buffy coat.

Results: Pregnancy in SLE patients with APS was associated with platelet and neutrophil activation that has functional procoagulant activity evidenced by surface thrombin generation, despite standard of care therapy with LMWH and ASA, and treatment of their underlying SLE with immunosuppression.

Conclusion(s): Further research will focus on identifying the mechanisms underlying platelet activation and platelet-leukocyte interactions and their prothrombotic effects in SLE/APS.

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ISTH Congress Abstracts - https://abstracts.isth.org/abstract/platelets-and-neutrophils-co-drive-procoagulant-potential-in-antiphospholipid-syndrome-during-pregnancy/