Neutrophil granules: a library of innate immunity proteins.

Gene expression profiling has revealed that circulating neutrophils rest between two major bursts of transcriptional and protein synthetic activities. The first occurs in the bone marrow. This equips the neutrophil with stocks of innate defense armory that are packaged into different granule subsets. The second burst occurs when the neutrophil exits circulation and migrates into tissues to find, capture and phagocytose microorganisms. This burst results in the synthesis and secretion of cytokines and chemokines that support resolution of inflammation and healing of damaged tissue. Gene expression profiling has revealed that neutrophils express a variety of innate immunity proteins, known previously only to be expressed in other cells. Likewise, it has become clear that some proteins previously thought to be specific to the neutrophil are expressed in epithelial cells during inflammation.