
<ArticleTitle>Dimeric <prot>S100A8</prot> in human neutrophils is diminished after phagocytosis.</ArticleTitle>
<AbstractText><prot>S100A8</prot> is a major cytoplasmic protein of neutrophils and monocytes/macrophages and has been associated with myeloid cell differentiation and activation. Little is known about its functions or mechanisms of release from neutrophils. We have developed a monoclonal antibody to murine <prot>S100A8</prot>, which cross-reacts with human <prot>S100A8</prot>. This antibody, which recognizes the homodimeric form of the protein, detects its expression specifically in human neutrophils and is reactive in formalin-fixed, paraffin-embedded tissues. Using this antibody as well as a commercially available antibody to human <prot>S100A8</prot>, we show that phagocytic activation of neutrophils, in vivo in acute appendicitis and in vitro following phagocytosis of opsonized zymosan, is characterized by loss of cytoplasmic immunoreactivity for <prot>S100A8</prot>. In vitro, phagocytosis is associated with rapid diminution of immunostaining without loss of viability. Loss of immunoreactivity for <prot>S100A8</prot> may serve as a marker of localized neutrophil activation in tissues.</AbstractText>
