title: From genotypes of immunoglobulin constant heavy G chains (Fcγ) (GM) genes (IGHG) to phenotypes in childhood asthma.
abstract: BACKGROUND
  IgE-mediated allergy is associated with immunoglobulin heavy constant G chain (Fcγ) (GM) genes (IGHG) on chromosome 14q32.3. Investigation of the alternative GM allotypes of γ3, γ1 and γ2 chains has disclosed new structural and functional IgG subclasses and B-cell variants, with possible effects on childhood asthma.
  
  
  OBJECTIVE
  To investigate different IGHG (GM) gene complexes in a childhood asthma population for allergy parameters.
  
  
  METHODS
  IGHG alleles and correlated allotypic (allelic) IgG subclass levels were analyzed with a sensitive indirect competitive ELISA in 10-year-old children with bronchial asthma. Individual IGHG diplotype-, genotype- and haplotype-related B cells were compared for allelic IgG subclass levels, IgE sensitization, IgE, IgA and IgM levels, and numbers of peripheral blood eosinophils and lymphocytes.
  
  
  RESULTS
  The group with homozygous IGHG*bfn/*bfn (B1/B1 cells) demonstrated low IgG1*f levels (p < 0.001) but increased IgG2*n levels (p < 0.001) together with increasd IgE and IGHG2*n gene dose-dependent IgE sensitization (atopic phenotype). The IGHG*bf-n/*bf-n (B2/B2 cells) demonstrated low IgG1*f (p < 0.05) and IgG2*-n (p < 0.001) and the IGHG*ga-n/*ga-n (B4/B4 cells) low IgG1*a (p < 0.001) and IgG2*-n (p < 0.02) together with low IgE sensitization (non-atopic phenotype). B*(bfn) (B1) and B*(bf-n) (B2) demonstrated increased numbers of peripheral blood eosinophils, compared to B*(gan) (B4) cells, which demonstrated increased peripheral blood CD8 lymphocytes instead.
  
  
  CONCLUSIONS
  IGHG diplotypes present different phenotypes in childhood asthma. The IGHG2*n dose relationship to IgE sensitization and increased IgG2*n levels in IgE sensitized are risk markers for IgE-mediated asthma. The opposite IGHG2*-n presents non-IgE-mediated asthma and IgG subclass deficiencies.
authors.affiliation: Department of Pediatrics and Institute of Laboratory Medicine, Department of Clinical Immunology, University Hospital, Lund University, Lund, Sweden. vivi-anne.oxelius@med.lu.se
authors.forename: Vivi-Anne
authors.initials: VA
authors.lastname: Oxelius
mesh_terms: D000293:Adolescent; D001249:Asthma / Q000097:blood / Q000235:genetics* / Q000276:immunology; D002648:Child; D004804:Eosinophils / Q000276:immunology; D005838:Genotype; D006801:Humans; D007142:Immunoglobulin gamma-Chains / Q000235:genetics*; D007136:Immunoglobulins / Q000097:blood; D007958:Leukocyte Count; D008214:Lymphocytes / Q000276:immunology; D010641:Phenotype
chemical_list: D007142:Immunoglobulin gamma-Chains; D007136:Immunoglobulins