HMGB1 and infection: Thus, it seems that preformed HMGB1 is rapidly liberated particularly from the airways epithelium which showed the strongest HMGB1 immunostaining during early infection; also the immunoelectronmicroscopy study indicated active secretion, as suggested by the observation that some cytoplasmic vesicles with labeled HMGB1 were fused to the apical membrane liberating the protein to the extracellular space.