Certain autoantibodies to phosphatidylethanolamine (aPE) recognize factor XI and prekallikrein independently or in addition to the kininogens

Recent evidence shows that many antiphospholipid antibodies (aPL) to negati vely-charged phospholipid (PL) do not target anionic PL per se, but are spe cific for anionic PL-binding plasma proteins, for example, beta (2)-glycopr otein I (beta (2)-GPI) and prothrombin. We also reported that certain antip hosphatidylethanolamine antibodies (aPE) are not specific for phosphatidyle thanolamine (PE) per se, but are directed to PE-binding plasma proteins, hi gh molecular weight kininogen (HK), and low molecular weight kininogen (LK) . Additional studies have shown that certain aPE failed to recognize purifi ed kininogens but continued to produce aPE ELISA reactivity in the presence of semipurified HK preparations containing the HK binding proteins, factor XI (FXI) and prekallikrein (PK). We therefore investigated if certain of t hese aPE recognized.,FXI and/or PK. In this study we observed that aPE can recognize contact proteins FXI and PK independently or in combination with HK. Since contact proteins such as HK, PK and factor XII (FXII) have anti-c oagulant and profibrinolytic functions, the pathophysiological role of aPE has yet to be elucidated. We propose that aPE of different specificities ma y initiate or promote characteristics pathological conditions in patients w ith thrombosis or recurrent pregnancy losses. (C) 2001 Academic Press.