Changing world of neutrophils.

Neutrophilic granulocytes are no longer regarded as cells involved only in the last phase of the immune response with one single-although vitally important-task: engulfing and killing of microorganisms marked by immunoglobulin or complement fragments. In recent years, it was shown that neutrophils are actively involved in initiation and organization of the adaptive immune response by releasing various cytokines, interacting with all major types of immune cells, regulating their own lifespan, and participating in the anaphylactic reaction and in several classically nonimmune functions such as hemostasis, atherogenesis, and even insulin resistance. The antibacterial effect is no longer restricted to killing and destruction of microorganisms sequestered in the phagosomal space. Bacteriostasis also occurs at certain locations of the extracellular space, by formation of neutrophil extracellular traps (NETs) that were shown in the last 2 years to have a significant role in the prevention of dissemination of microorganisms. Extracellular vesicles represent a recently discovered form of intercellular communication carried out both by lipids, proteins, and nucleic acids. In this review, we also summarize the role of neutrophil-derived extracellular vesicles in modifying the function of other cell types as well as their direct antibacterial effect that differs significantly from mechanisms applied either by neutrophils or by the NETs.