Objective: The aim of the study is to investigate the in vivo pathogenic role of toll like receptor-4 (TLR- 4) in the anti-phospholipid syndrome (APS) by looking at the thrombogenic aPL activity in LPS non-responsive (LPS- /-) mice and at the association between tlr4 gene polymorphisms and APS in patients.
Methods: IgGs from two APS patients, one aPL- negative Systemic Lupus Erythematosus (SLE) patient and one normal human serum (NHS) were evaluated for thrombosis, Tissue Factor (TF) activity and endothelial cell activation in LPS-/- mice displaying a tlr4 spontaneous mutation vs LPS-responsive (LPS+/+) mice. Human tlr4 Asp299Gly and Thr399Ile polymorphisms were evaluated by allele-specific polymerase chain reaction in 110 APS patients with arterial/venous thrombosis and in 220 controls of the same ethnic origin.
Results: IgG-APS produced significantly larger thrombi and number of adhering leukocytes (WBC) to endothelial cells in the cremaster muscle microcirculation of LPS +/+ mice when compared to IgG- NHS or aPL-negative SLE-IgG. These effects were abrogated after absorption of the anti-?2glycoprotein I activity by an affinity column. The two IgG-APS induced significantly smaller thrombus size and lower number of endothelial WBC adhering in LPS -/- compared to LPS +/+ mice. IgG-APS induced higher TF activity in carotid artery homogenates of LPS +/+ compared to LPS -/- mice. Asp299Gly and Thr399Ile tlr4 polymorphism prevalence was significantly lower than in controls.
Conclusions: The findings in LPS -/- mice and the reduction in the “protective” polymorphism in APS patients with thrombosis suggest that TLR-4 is involved in in vivo aPL interaction with endothelial cells.
- antiphospholipid antibodies
- antiphospholipid syndrome
- endothelial cells
- tissue factor