title: Cytotoxic granule secretion by lymphocytes and its link to immune homeostasis.
abstract: The granule-dependent cytotoxic activity of T and natural killer lymphocytes has progressively emerged as an important effector pathway not only for host defence but also for immune regulation. The analysis of an early-onset, severe, primary immune dysregulatory syndrome known as hemophagocytic lymphohistiocytosis (HLH) has been decisive in highlighting this latter role and identifying key effectors on the basis of gene mutation analyses and mediators in the maturation and secretion of cytotoxic granules. Studies of cytotoxicity-deficient murine counterparts have helped to define primary HLH as a syndrome in which uncontrolled T-cell activation in response to lymphocytic choriomeningitis virus infection results in excessive macrophage activation and inflammation-associated cytopenia. Recent recognition of late-onset HLH, which occurs in a variety of settings, in association with hypomorphic, monoallelic mutations in genes encoding components of the granule-dependent cytotoxic pathway or even in the absence of such mutations has broadened our view about the mechanisms that underlie the perturbation of immune homeostasis. These findings have led to the development of a model in which disease occurs when a threshold is reached through the accumulation of genetic and environmental risk factors. Nevertheless, validation of this model will require further investigations.
authors.affiliation: INSERM UMR1163, Laboratory of Normal and Pathological Homeostasis of the Immune System, Paris, F-75015, France ; Paris Descartes University-Sorbonne Paris Cité, Imagine Institute, Paris, F-75015, France ; Centre d'Etudes des Déficits Immunitaires, Assistance Publique-Hôpitaux de Paris, Assistance Publique-Hôpitaux de Paris, Paris, France.
authors.forename: Geneviève
authors.initials: G
authors.lastname: de Saint Basile
authors.affiliation: INSERM UMR1163, Laboratory of Normal and Pathological Homeostasis of the Immune System, Paris, F-75015, France ; Paris Descartes University-Sorbonne Paris Cité, Imagine Institute, Paris, F-75015, France.
authors.forename: Fernando E
authors.initials: FE
authors.lastname: Sepulveda
authors.affiliation: INSERM UMR1163, Laboratory of Normal and Pathological Homeostasis of the Immune System, Paris, F-75015, France ; Paris Descartes University-Sorbonne Paris Cité, Imagine Institute, Paris, F-75015, France.
authors.forename: Sophia
authors.initials: S
authors.lastname: Maschalidi
authors.affiliation: INSERM UMR1163, Laboratory of Normal and Pathological Homeostasis of the Immune System, Paris, F-75015, France ; Paris Descartes University-Sorbonne Paris Cité, Imagine Institute, Paris, F-75015, France ; Immunology and Pediatric Hematology Department, Necker Children's Hospital, AP-HP, Paris, France ; Collège de France, Paris, F-75005, France.
authors.forename: Alain
authors.initials: A
authors.lastname: Fischer
keywords: cytotoxic; haemophagocytic lymphohistiocytosis; natural killer lymphocytes