Anti-Protein S and Anti-Phosphatidylethanolamine (aPE) Antibodies in Patients with Clinical Features of Antiphospholipid Syndrome (APS)

Abstract number: P1807

Sanmarco¹ M, Bardin^1,2 N, Roll¹ P, Dignat-George^1,2 F, Alessi³ MC

^{1,2 1,2 11}Hôpital de La Conception, Marseille, France ³³Hôpital de La Timone, Marseille, France

Purpose:  Anti-protein S antibodies (anti-protein S) and aPE have been reported as associated with clinical events of APS. Our aim was to determine prevalence, relationship with aPE and free protein S, and clinical significance of anti-protein S in patients having clinical features of APS.

Patients and methods:  145 patients were included (M/F = 22/123; mean age = 42 years). From them, 75% had thrombotic events and 27% pregnancy loss. These patients were divided into 2 groups, one including 47 patients positive for aPE and negative for anti-cardiolipin antibodies (aCL) or Lupus anticoagulant (LA); the other one with 98 patients negative for aPE (62 negative and 36 positive for aCL or LA). Fifty healthy blood donors comprised the control group. All patients were tested for anti- protein S and aPE (IgG or IgM) by in house ELISA.

Results:  The prevalence of anti-protein S was significantly higher in patients than in controls (33% vs 2%, P < 0.0001). They were significantly more frequent in patients positive for aPE than in those negative (53% vs 24%, P < 0.0001) while they appeared to be independent of aCL or LA. IgM isotype of anti- protein S was found predominant in all patients (77%) whether they were positive or negative for aPE. No correlation was found between anti- protein S and free protein S levels. Prevalence of anti-protein S was similar in patients with thrombosis or pregnancy loss (32% and 39%, respectively).

Conclusion:  Overall, our data show that anti- protein S are frequent in patients with clinical features of APS and their presence is highly associated with that of aPE but not that of aCL or LA.