SerpinB1: A Global Regulator of Neutrophil Homeostasis

SerpinB1 is an inhibitory serpin, which is broadly expressed at highly variable levels. It is encoded by an ancient gene—possibly the extant homologue of the serpin gene at the root of the clade B tree. Studies of gene-deleted mice in models of lung injury, infection, and inflammation identified SerpinB1 as a protective anti-inflammatory immunomodulator. Other studies document its disparate cell-specific functions. Here we review these studies and present a unifying hypothesis, which is that the multiplicity and diversity of known functions each reflects a different aspect of SerpinB1’s overruling function as a global regulator of neutrophil homeostasis.