Anti-β2GP1 antibodies have variable effects on platelet aggregation

Area of Science:

• Immunology
• Hematology
• Rheumatology

Background:

• Antiphospholipid antibodies, including anti-beta2 glycoprotein 1 (anti-β2GP1), are associated with thrombosis in systemic lupus erythematosus (SLE).
• The precise role of anti-β2GP1 in platelet activation and aggregation remains incompletely understood.
• Understanding these interactions is crucial for managing thrombotic risks in SLE patients.

Purpose of the Study:

• To investigate the differential effects of affinity-purified rabbit anti-β2GP1 and human anti-β2GP1 from SLE patients on adenosine diphosphate (ADP)-induced platelet aggregation.
• To compare the impact of species-derived anti-β2GP1 on key parameters of platelet aggregation.

Main Methods:

• Platelet-poor plasma (PPP) was obtained from 15 healthy controls and 15 SLE patients.
• Anti-β2GP1 titers were measured by ELISA, and IgG fractions were isolated.
• Light transmission aggregometry was used to assess the effects of rabbit and human anti-β2GP1 on ADP-induced platelet aggregation.

Main Results:

• Rabbit anti-β2GP1 significantly inhibited all measured parameters of ADP-induced platelet aggregation (%Max, %AUC, slope).
• In contrast, human anti-β2GP1 from SLE patients significantly enhanced %Max and %AUC in a concentration-dependent manner, while inhibiting the slope.
• These contrasting effects were observed with 5 μM ADP-induced aggregation.

Conclusions:

• Anti-β2GP1 purified from different species exhibit variable effects on in vitro platelet aggregation.
• The observed disparities may stem from the heterogeneous nature of anti-β2GP1, differences in avidity, or distinct antibody binding specificities between rabbit and human antibodies.
• These findings underscore the complexity of anti-β2GP1's role in platelet function and thrombosis.