A fluorescent reporter mouse for inflammasome assembly demonstrates an important role for both cell bound and free ASC specks during in vivo infection

Abstract

Abstract Inflammasome activation is associated with numerous diseases. However, in vivo detection of the activated inflammasome complex has been limited by a dearth of tools. We developed transgenic mice that ectopically express the fluorescent adaptor protein, ASC (apoptosis-associated speck-like protein containing a caspase recruitment domain), and characterized the formation of assembled inflammasome complexes (“specks”) in primary cells and tissues. In addition to hematopoietic cells, we found that a stromal population in the lung tissues forms specks during the early phase of influenza infection whereas myeloid cells showed speck formation after two days. In a peritonitis and Group B streptococcus infection models, a higher percentage of neutrophils formed specks at early phases of infection, while dendritic cells formed specks at later time points. Furthermore, speck-forming cells underwent pyroptosis, and extensive release of specks to the extracellular milieu in vivo. These data underscore the importance of free specks during inflammatory processes in vivo.