Early-onset inflammatory bowel disease and common variable immunodeficiency-like disease caused by IL-21 deficiency
Résumé
BACKGROUND: Alterations of immune homeostasis in the gut can result in development of inflammatory bowel disease (IBD). Recently, Mendelian forms of IBD have been discovered, as exemplified by deficiency of IL-10 or its receptor subunits. In addition, other types of primary immunodeficiency disorders might be associated with intestinal inflammation as one of their leading clinical presentations. OBJECTIVE: We investigated a large consanguineous family with 3 children who presented with early-onset IBD within the first year of life, leading to death in infancy in 2 of them. METHODS: Homozygosity mapping combined with exome sequencing was performed to identify the molecular cause of the disorder. Functional experiments were performed to assess the effect of IL-21 on the immune system. RESULTS: A homozygous mutation in IL21 was discovered that showed perfect segregation with the disease. Deficiency of IL-21 resulted in reduced numbers of circulating CD19(+) B cells, including IgM(+) naive and class-switched IgG memory B cells, with a concomitant increase in transitional B-cell numbers. In vitro assays demonstrated that mutant IL-21(Leu49Pro) did not induce signal transducer and activator of transcription 3 phosphorylation and immunoglobulin class-switch recombination. CONCLUSION: Our study uncovers IL-21 deficiency as a novel cause of early-onset IBD in human subjects accompanied by defects in B-cell development similar to those found in patients with common variable immunodeficiency. IBD might mask an underlying primary immunodeficiency, as illustrated here with IL-21 deficiency.
Mots clés
Humans
Female
Male
Mutation
Signal Transduction
Models
Molecular
Amino Acid Sequence
Molecular Sequence Data
Child
Infant
Age of Onset
Preschool
Immunophenotyping
B-Lymphocyte Subsets/immunology/metabolism
Common Variable Immunodeficiency/*genetics/immunology/metabolism
Consanguinity
DNA Mutational Analysis
Immunoglobulin Class Switching
Immunoglobulin Isotypes/blood/immunology
Inflammatory Bowel Diseases/*genetics/immunology/metabolism
Interleukins/chemistry/*deficiency/*genetics
Lymphocyte Activation
Pedigree
Protein Conformation
Receptors
Interleukin-21/metabolism
Sequence Alignment