CD40LG and antiphospholipid syndrome: Furthermore, anti-phospholipid antibodies are essential clinical criteria in the anti-phospholipid syndrome (APS) diagnosis, a systemic autoimmune disease in which specific laboratory markers, such as lupus anticoagulant (LAC), IgG and/or IgM anti-cardiolipin (aCL), and IgG and/or IgM anti-β2-glycoprotein-1 (aβ2GP1) antibodies, are crucial to the diagnosis.