par Huygens, Ariane ;Marchant, Arnaud
Référence Fetal Therapy: Scientific Basis and Critical Appraisal of Clinical Benefits, Cambridge University Press, page (200-207)
Publication Publié, 2009-01
Partie d'ouvrage collectif
Résumé : Introduction The immune system of the fetus normally develops in a sterile environment. This developmental process prepares the fetus for the challenge of controlling a large diversity of infectious pathogens after birth. Following congenital infections with viruses, bacteria, or protozoans, the fetal immune system is challenged to generate anti-microbial effector functions while it is still primarily controlled by its developmental program. The immune system of the fetus has long been considered as non-reactive or prone to tolerance to foreign antigens. Recent clinical studies have demonstrated that immune effector functions can develop during fetal life. This chapter first provides an overview of the immune system and describes current knowledge of its development during fetal life. The capacity of the fetal immune system to respond to infectious pathogens is then summarized, focusing on the most studied congenital infections. The immune system at a glance The immune system is composed of different cell types having specific and inter-related functions. In tissues, immune cells like macrophages and dendritic cells (DCs) express specific receptors, such as Toll-like receptors (TLRs), allowing them to recognize molecules called pathogen-associated-molecular-patterns (PAMPs) that are specifically expressed by pathogens. The interaction with PAMPs activates cells to produce inflammatory cytokines attracting other immune cells such as neutrophils and monocytes to the site of infection. Neutrophils are mainly involved in the phagocytosis and the intracellular killing of pathogens. Monocytes differentiate into macrophages and DCs which have phagocytic properties and activate T lymphocytes.