ABSTRACT
The first line of defense against infection is the innate immune system, and activation occurs when a pathogen breaches the host's natural barriers. The acquired immune system has evolved relatively recently and is built upon the phylogenetically older innate immune system, by which it is controlled and assisted. Neutropenia commonly develops in neonatal sepsis in contrast to the leukocytosis in septic adults. This may be mediated by a decreased neutrophil storage pool and a limited capacity for increased progenitor production in newborns especially preterms. The crucial role of monocytes/macrophages in the immune response resides in their accessory cell and immunoregulatory functions of both humoral and cellular immunity. The toll-like receptors (TLR) provide the critical link between microbial immune stimulants and initiation of host defense. Necrotizing enterocolitis (NEC) is one of the most devastating diseases in newborns. It is associated with loss of gut integrity and immune dysfunction.
