CD40LG and antiphospholipid syndrome: It is interesting to note that, although 2006 Sydney antiphospholipid syndrome classification criteria has included IgG/IgM anti-cardiolipin, IgG/IgM anti-β2-glycoprotein antibodies and lupus anticoagulant, some patients suffering from antiphospholid syndrome still remain sero-negative (sero-negative APS or SNAPS).