Host defense to intracellular pathogens depends upon both innate and adaptive cell-mediated immune responses. Polymorphonuclear neutrophil leukocytes which belong to the innate immune system are the first cells that are recruited massively within hours of microbial infection. The importance of neutrophils in the development of an immune response is only emerging as they have long been considered by immunologists as short lived, non-dividing cells, of poor interest. Now, neutrophils are emerging as key components of the inflammatory response, and are shown to have immunoregulatory roles in microbial infections. The impact of neutrophils on cells present at the site of infection is only beginning to be studied and deserves more attention. This e-book provides an overview of the recent advances made in the field of neutrophil biology and motions towards some of the exciting new directions in which neutrophil research is moving.