Extracellular acidosis promotes neutrophil transdifferentiation to MHC class II-expressing cells

► Acidosis enhances cytokine-induced expression of MHC class II in neutrophils. ► Acidosis potentiates antigen uptake by MHC class II-expressing neutrophils. ► Acidosis potentiates antigen presentation by MHC class II-expressing neutrophils. Inflammation in peripheral tissues is usually associated with local acidosis. In the present study, we demonstrate that extracellular acidification enhances GM-CSF- and IFN- γ-induced expression of HLA-DR, CD80 and CD86 in human neutrophils (neutrophil transdifferentiation), and potentiates antigen-capturing capacities (both endocytosis and phagocytosis) of the transdifferentiated cells. Furthermore, in acidic conditions the transdifferentiated neutrophils have stronger antigen-presenting capacity, inducing more intense proliferation of autologous T lymphocytes in the presence of staphylococcal enterotoxin A. Thus, extracellular acidosis can represent a factor that promotes neutrophil transdifferentiation and potentiates the functional abilities of the transdifferentiated cells in inflammatory foci in vivo.