title: Humoral immune responses and CD27+ B cells in children with DiGeorge syndrome (22q11.2 deletion syndrome).
abstract: The spectrum of T-cell abnormalities in 22q11.2 syndrome is quite broad, ranging from profound and life threatening to non-existent defects. Humoral abnormalities have been described in some of these patients, although no data are currently available on their phenotypical and functional B cell subsets. The purpose of this study was to investigate humoral immune function in a cohort of 13 children with DiGeorge syndrome by immunophenotyping B and by analysing their functionality in vivo. Humoral immunity was assessed by serum immunoglobulin evaluation, IgG subclasses determination, and testing of specific antibody titers to recall antigens. B cells were analyzed by flow cytometry and the relevant percentage of membrane surface expression of CD27, IgM, IgD was evaluated. In our cohort, one of 13 children (7.7%) had a complete IgA deficiency, four of 13 (30.7%) had minor immunoglobulin abnormalities, and five (38%) had an impaired production of specific antibodies. Five of 13 children (38%) had recurrent infections. Interestingly, peripheral CD27+ B cells were reduced in our patients as compared with age-matched healthy controls, and this decrement was statistically significant for IgM+ IgD+ CD27+ B cells. Immunoglobulin abnormalities were associated with the occurrence of recurrent infections. We conclude that a significant proportion of patients with DiGeorge syndrome have defective humoral immunity, which may represent an additional pathogenic mechanism underlying the increased susceptibility to infections. Whether the decreased CD27+ B-cell subset might be one of the defects that contribute to impaired humoral immunity, and to susceptibility to infection remains to be elucidated.
authors.affiliation: Department of Paediatrics, Tor Vergata University, Rome, Italy. andrea.finocchi@uniroma2.it
authors.forename: A
authors.initials: A
authors.lastname: Finocchi
authors.forename: S
authors.initials: S
authors.lastname: Di Cesare
authors.forename: M L
authors.initials: ML
authors.lastname: Romiti
authors.forename: C
authors.initials: C
authors.lastname: Capponi
authors.forename: P
authors.initials: P
authors.lastname: Rossi
authors.forename: R
authors.initials: R
authors.lastname: Carsetti
authors.forename: C
authors.initials: C
authors.lastname: Cancrini
mesh_terms: D000917:Antibody Formation / Q000276:immunology; D018941:Antigens, CD19 / Q000276:immunology; D001402:B-Lymphocytes / Q000276:immunology*; D017252:CD3 Complex / Q000276:immunology; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology; D002675:Child, Preschool; D015331:Cohort Studies; D004062:DiGeorge Syndrome / Q000235:genetics / Q000276:immunology*; D005260:Female; D006801:Humans; D007070:Immunoglobulin A / Q000276:immunology; D016130:Immunophenotyping; D007223:Infant; D016131:Lymphocyte Subsets / Q000276:immunology; D008297:Male; D018127:Tumor Necrosis Factor Receptor Superfamily, Member 7 / Q000276:immunology*
chemical_list: D018941:Antigens, CD19; D017252:CD3 Complex; D007070:Immunoglobulin A; D018127:Tumor Necrosis Factor Receptor Superfamily, Member 7