Anti-β₂-Glycoprotein I Autoantibody Expression as a Potential Biomarker for Strokes in Patients with Anti-Phospholipid Syndrome

Abstract

Anti-phospholipid syndrome (APS) is an autoimmune disease. Cerebral ischemia associated with APS occurs at a younger age than typical atherothrombotic cerebrovascular disease, is often recurrent, and is associated with high positive IgG anti-phospholipid (GPL) unit levels. This study sought to determine the frequency rates of anti-cardiolipin (aCL) dependent on the presence of β₂-GPI, anti-β₂-glycoprotein I (aβ₂-GPI), and anti-phosphatidyl serine (aPS) IgG autoantibodies among stroke patients, and thus demonstrate the importance of testing for aβ₂-GPI autoantibodies. For these study, stroke patients and control subjects recruited from Mosul, Erbil, and Dohuk provinces in Northeren Iraq between March 2004 and March 2005 were evaluated. All cases were under 50 years-of-age and had no recognizable risk factors. Using ELISA to evaluate the presence of IgG isotype of aCL, aβ₂-GPI, and aPS autoantibodies in their blood, the results indicated that the frequency of aβ₂-GPI was 14/50 (28%), aCL was 11/50 (22%), and aPS was 9/50 (18%) among stroke patients. In contrast, aCL was detected in 2/30 (6.7%) of control subjects; each of the other anti-phospholipid antibodies (APLA) was never observed. Of all the aβ₂-GPI⁺ cases, the incidence of stroke patients having the combined profile of aβ₂-GPI + aCL was 11/14 (78.6%) and of aβ₂-GPI + aPS was 9/14 (64.3%). Only 2/14 (14.3%) of these aβ₂-GPI⁺ patients also expressed aCL in the absence of aPS. The frequency of patients expressing all three markers was only 9/14 (64.3 %). In none of the APS/stroke patients were aCL or aPS expressed in the absence of the aβ₂-GPI. Conversely, aβ₂-GPI as a sole marker was seen in 3/14 (21.4%) of these patients (i.e., in absence of either other marker). It can be concluded from these studies that the among the three major forms of APLA examined, the presence of aβ₂-GPI IgG autoantibodies appeared to correlate best with stroke in patients who were concurrently suffering APS.

Keywords :

• Anti-β₂-glycoprotein I
• autoantibodies
• stroke