Neutrophils induce the maturation of immature dendritic cells: A regulatory role of neutrophils in adaptive immune responses

Th1-type immune cytokines are essential to establish adaptive immunity against various microbial pathogens, including Escherichia coli, which cause most urinary tract infections ( UTIs). Dendritic cells ( DCs) are vital to initiate Th1 immunity, while neutrophils, also referred to here as polymorphonuclear leukocytes ( PMN) are reported to be involved in Th1 immunity initiation by secreting several chemokines and cytokines. We found that lipopolysaccharide ( LPS)-triggered PMN ( LPS-PMN) in vitro induced strong up-regulation of DCs surface markers CD40, CD80, MHC-II ( Ia(b)), and CD86 either by secreting soluble factors, such as TNF-alpha, or by PMN-DC cellular contact. LPS-PMN also stimulated DCs to produce IL-12 and TNF-alpha. Furthermore, purified DCs activated by LPS-PMN were able to present specific antigen to T cells and drive Th1 differentiation by producing large amount of IFN-gamma but low amount of IL-4. Our results suggest a regulatory role of PMN for DCs function in adaptive immune responses, thereby providing a link between innate and adaptive immunity.