Neutrophils: Interplay between host defense, cellular metabolism and intracellular infection.

Neutrophils are short-living innate immune cells present in abundance in the circulation and they provide the first line of defense against infection. Microbicidal effector functions of the immune cells are tightly linked with their metabolic state. Overall knowledge of the association of neutrophil defense with cellular metabolism is still elusive. Recent studies have reported that neutrophil metabolism during granulopoiesis is impacted by the homeostatic process of autophagy. Autophagy is a complex process of which the subtype xenophagy, an antimicrobial autophagic process, clears invading pathogens. Neutrophils, being sentinels of innate immunity, encounter microbes and digest them. Studies on neutrophil antimicrobial autophagy process is still in its primeval state and has not been much explored as in other professional phagocytes. However, several obligate-intracellular pathogens are able to subvert the toxic antimicrobial machineries and utilize neutrophils as their final abodes or "Trojan Horses" for further propagation. In this review, we would provide an insight into the relationship between neutrophil microbicidal effector functions emphasizing on selective antimicrobial autophagy and metabolism, highlighting on some successful pathogens which have evolved ways to subvert or exploit this defense.