In order to evaluate whether autoantibodies in APS may be able to elicit the alarmin response, we preliminary analyzed in vitro whether anti-β2-GPI antibodies from APS patients may induce both a HMGB1 relocation to cytosol and an activation of its putative receptor RAGE in monocytes from healthy donors. Here, HMGB1 is linked to autoimmune polyendocrinopathy.