PS

The first study of anti-phospholipid antibodies began in 1906, when Wasserman introduced a serological test for syphilis. In 1942, the active component was found to be a phospholipid, which was designated cardiolipin. In the 1950s it became clear that a number of people had positive tests for syphilis without any evidence of the disease. This phenomenon was referred to as the biological false positive serological test for syphilis. A high prevalence of autoimmune disorders, including systemic lupus erythematosus (SLE) and Sj?gren′s syndrome occurred in this group of patients. The presence of circulating anticoagulants in patients with SLE was first documented in 1952 and was associated with increased risk of paradoxical thrombosis in 1963. The term lupus anticoagulant (LA), first used in 1972, is clearly a misnomer, because LA is more frequently encountered in patients without lupus and is associated with thrombosis rather than abnormal bleeding. During the last years it became clear that the optimal binding of anti-phospholipid antibodies is depending on a cofactor termed beta-2-glycoprotein I (apolipoprotein H) (β2GPI). β2GPI is a 50 kDa beta-2-globulin occurring in plasma at a level of 200 μg/ml. It has been found that beta-2-Glycoprotein I inhibits the intrinsic coagulation pathway and, therefore, it is involved in the regulation of blood coagulation. β2GPI is associated in vivo with negatively-charged substances, e.g. anionic phospholipids, heparin and lipoproteins. The phospholipid binding region is located on its fifth domain. Under the acronym "aPL" (anti-phospholipid antibodies) antibodies against negatively-charged phospholipids, such as CL (cardiolipin), LA (lupus anticoagulant), PS (phosphatidyl serine), PI (phosphatidyl inositol) and PA (phosphatidic acid) are summarised. Of these, cardiolipin is the phospholipid most commonly used as antigen to test for aPL by ELISA. Some antisera which bind cardiolipin-coated ELISA plates can also bind to plates coated with other negatively-charged phospholipids, such as phosphatidyl serine (PS), phosphatidyl inositol and phosphatidic acid (PA). Some investigators have suggested that the use of PS in place of cardiolipin in ELISA tests enables more specific diagnosis. These antigens are less commonly used and their additional use can improve the clinical sensitivity in patient samples with suspected APS (anti-phospholipidsyndrome), but they can't replace the measurement of autoantibodies against cardiolipin. The Scientific and Standardization Committee of the International Society on Thrombosis and Hemostasis has issued consensus criteria that may be used to help laboratory diagnosis.

Phosphatidyl Serine; Phosphatidylserine; Ptd-L-Ser; PS;