HMGB1 (High Mobility Group Box-1 protein also known as amphoterin) is a highly conserved protein with more than 95% amino acid identity between rodent and human HMGB1. It is a prevalent non-histone chromatin component and a non-sequence specific DNA binding protein. HMGB1 consists of two homologous HMG boxes rich in basic amino acids and an acidic tail at the carboxy-terminus. HMGB1 is involved in the regulation of chromatin structure as well as being involved, either as positive or negative factors with various aspects of DNA replication, transcription, repair, and ligation. HMGB1, identified as a membrane associated protein termed “amphoterin,” mediates neurite outgrowth, tumor outgrowth, and metastasis. It participates in plasminogen activation and is recognized as a late mediator of endotoxin lethality in mice. The monoclonal antibody anti HMGB1, clone 5H6, can be used for Western blot, Flow cytometry and Immunofluorescence.