Monocytic cell differentiation from band-stage neutrophils under inflammatory conditions

During inflammation, neutrophils are rapidly mobilized from the bone marrow storage pool into peripheral blood to subsequently enter lesional sites where most of them rapidly undergo apoptosis. Monocytes constitute a second wave of inflammatory immigrates giving rise to long-lived macrophages and dendritic cell subsets. According to descriptive immunophenotypic and cell culture studies, neutrophils may directly “transdifferentiate” into monocytes/macrophages. We here provide mechanistic data in human supporting the existence of this cellular pathway. Global transcriptional profiling of neutrophil-dervived monocytic cells revealed close resemblance of gene expression with monocytes and a clear separation of these cells from neutrophils. G-CSF mobilized neutrophils from peripheral blood were isolated and in vitro stimulated with GM-CSF, TNFa, and Il-1b for 5 days to generate monocytic cells. RNA were isolated from these cells and freshly isolated blood neutrophils and monocytes.