Neutrophil plasticity: acquisition of phenotype and functionality of antigen-presenting cell

Accumulating lines of evidence now demonstrate that neutrophils can participate in adaptive immune responses directly or indirectly. Even more striking is their potential to acquire phenotypic and functional properties that are typically reserved for professional APCs. These newly emerging concepts of neutrophil heterogeneity and plasticity now challenge the classic view of neutrophils as terminally differentiated leukocytes fully committed to phagocyte functionality. Here, we present a brief overview of our current understanding of neutrophil plasticity by focusing on the acquisition of DC-like properties in culture and at sites of inflammation. Human and murine neutrophils acquire surface expression of MHC II, costimulatory molecules, and other surface markers of DCs when cultured in the presence of selected cytokines. The resulting populations also exhibit potent APC activities to present various antigens to T cells. "Unusual" neutrophils expressing DC markers have been detected in inflammatory lesions in human patients and mouse disease models. These findings imply that acquisition of DC-like properties by neutrophils at the sites of inflammation may represent a key process for linking the innate and adaptive arms of immune responses.