The alarmin functions of high-mobility group box-1 and IL-33 in the pathogenesis of systemic lupus erythematosus.

'Alarmins' are a group of endogenous proteins or molecules that are released from cells during cellular demise to alert the host innate immune system. Two of them, high-mobility group box-1 (HMGB1) and IL-33 shared many similarities of cellular localization, functions and involvement in various inflammatory diseases including systemic lupus erythematosus (SLE). The expressions of HMGB1 and IL-33, and their corresponding receptors RAGE (receptor for advanced glycation end products) and ST2, respectively, are substantially upregulated in patients with lupus nephritis (LN). This review highlights the emerging roles of alarmin proteins in various pathologies of LN, by focusing on classical HMGB1 and a newly discovered alarmin IL-33.