Mechanisms of anti-phospholipid antibody formation and action

The antiphospholipid syndrome is an autoimmune disease characterised by the clinical features of recurrent thrombosis in the venous or arterial circulation and foetal losses in combination with circulating anti-phospholipid antibodies in the blood of the afflicted patients. Over the last 25 years numerous studies have established the correlation between the presence of antibodies against anionic phospholipids and thrombo-embolic manifestations but how these antibodies cause thrombosis is still unclear. Most scientists now accept the fact that only a subset of the antiphospholipid antibodies has clinical relevance. Not antibodies to anionic phospholipids but rather antibodies to β2-glycoprotein I are thought to be the major cause for the pathological manifestations. β2-Glycoprotein I is a plasma protein without a known function and persons lacking β2-Glycoprotein I are completely healthy. Our challenge is to understand why auto-antibodies against such a dispensable protein are so common and how antibodies directed against a protein without obvious function can induce the severe clinical manifestations observed in this syndrome.