A novel physiological pathway in the regulation of neutrophil activation

Neutrophils are key participants in the innate immune system and the first responders to inflammatory stimuli. This rapid response of neutrophils is achieved by their polarization and migration towards inflammatory mediators, however the mechanisms that regulate these changes are only partly understood. Recent studies support a role for calpain I in regulating neutrophil polarization and directional migration to chemotactic stimuli. Our study reveals a previously unknown function for acute phase protein, α1-proteinase inhibitor or α1-antitrypsin (AAT) to inhibit calpain I and to activate the Rho GTPases, Rac and…