Immunocytochemical localization of peptidylarginine deiminase in human eosinophils and neutrophils.

Peptidylarginine deiminase, registered as PAD V in the DDBJ/GenBank/EMBL data banks, is expressed in HL-60 cells differentiated into granulocytes or monocytes. We analyzed PAD activities in density-fractionated human peripheral blood cell fractions. PAD activity with similar substrate specificity to that of PAD V was found in the eosinophil and neutrophil fractions, which showed single bands comigrating with authentic PAD V on immunoblotting with an anti-PAD V antibody. Both the biochemical and immunoblotting analyses showed marked enrichment of PAD V in the eosinophil fraction. Its immunoreactivity appeared to localize in eosinophilic granules at high density and in myeloperoxidase-negative cytoplasmic granules of neutrophils at low density, as determined by confocal laser-scanning microscopy. Possible roles of PAD V in myeloid differentiation and granulocyte function are discussed. In addition, we present evidence for the presence of PAD(s) that are antigenically different from PAD V in monocytes and lymphocytes.