Gm phenotype linkage to subsets of juvenile chronic arthritis (JCA) with influence on IgG subclass response

Innate IgG molecules and innate B cells expressed by immunoglobulin constant heavy G chain (Fcγ) genetic marker genes are involved in the 'allergic march' of IgE sensitization in children

BACKGROUND

Interindividual variations of immunoglobulin constant heavy G chain (IGHG) genes on chromosome 14q32.3 are identified by alternative genetic markers (GM) of IgG3, IgG1 and IgG2, respectively. They express structurally and functionally innate IgG molecules and B cells, associated with allergic disease, replicated in several studies.

MATERIALS AND METHODS

1-year-old and 10-year-old, IgE-sensitized and non-sensitized children from the German Multicenter Allergy Study birth cohort were assessed by new serological methods for the mendelian IGHG (Fcγ) (GM) genes, as innate IgG molecules and innate B cells.

RESULTS

Food allergy sensitization in thirty-five 1-year-old children (124 not sensitized) was associated with the IGHG*bfn haplotype and B*(bfn) cells (OR 1.9, 95% CI 1.2-3.1; p = 0.010). Aeroallergen sensitization in ninety-nine 10-year-old children (95 not sensitized) was associated with the same genes (OR 1.4, 95% CI 1.02-1.9; p = 0.034). The IgE sensitization was most prominent in the restrictive homozygous IGHG*bfn/*bfn diplotype, 34% at age 1, increasing to 60% at age 10, rating the highest numbers of positive IgE tests, expressing increased levels of IgE and innate IgG2*n.

CONCLUSIONS

The IGHG*bfn haplotype (B*(bfn) cells) and increased innate IgG2*n levels are predictive factors for IgE sensitization in childhood. IGHG genes can be assessed for prognostic and preventive purposes in clinical care.

Human immunoglobulin constant heavy G chain (IGHG) (Fcγ) (GM) genes, defining innate variants of IgG molecules and B cells, have impact on disease and therapy

The distinguished alternative GM allotypes localized in immunoglobulin constant heavy G chain IGHG (Fcγ) (GM) genes on chromosome 14q32.3 define two unique variants of respectively IgG3, IgG1 and IgG2 subclasses, with different structures and functions. The IGHG allele (allotypes), expressed in homozygous or heterozygous forms, are assessed by new serological methods. Fixed combinations of γ3, γ1 and γ2 allotypes constitute the haplotypes, which are indirect markers of B cells. We highlight the role of homozygous IGHG genes with restricted qualities of IgG subclass molecules and B cells. These common Mendelian IGHG genes respond differently to allergens and infections, both bacterial and viral, and to active and passive immunotherapies. IGHG genes have an impact on diseases such as allergy, immunodeficiency, autoimmunity and malignancy. Association/linkage of different IGHG genes gives information about risk/protection, good or bad prognosis, for improvement of clinical care. The IGHG gene map of healthy Caucasians is registered.

From genotypes of immunoglobulin constant heavy G chains (Fcγ) (GM) genes (IGHG) to phenotypes in childhood asthma

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.

CONCLUSION

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.

Immunoglobulin heavy G2 chain (IGHG2) gene restriction in the development of severe respiratory syncytial virus infection

AIM

Respiratory syncytial virus (RSV) is a prominent cause of airway morbidity in children under 1 y of age. It is assumed that host factors influence the severity of disease presentation, and thus the need for hospitalization. The variation of IGHG genes from chromosome 14q32 are linked to serum IgG subclass levels but also to the variations in IgG responses to pneumococcal, meningococcal and Haemophilus influenzae antigens. The aim of this investigation was to clarify whether IGHG genes are involved in the development of severe RSV lower respiratory tract infection (LRTI).

METHODS

The alternative expressions of IGHG3(b) and (g), IGHG1(f) and (a), and IGHG2(n) and (-n) genes were studied in a cohort of 49 previously healthy children hospitalized for RSV LRTI. The gene frequencies were compared to a population of healthy individuals.

RESULTS

The homozygous IGHG2(-n/-n) genotypes dominated in hospitalized children with severe RSV infection: 55.1%, compared with 34.2% in the healthy population (OR 2.3; p = 0.004). The IGHG2 genotypes containing (n/n) and (n/-n) were significantly decreased. The IGHG(bf-n) alleles were significantly increased (OR 1.7; p = 0.025) and the IGHG(bfn) alleles significantly decreased (OR 0.5; p = 0.005).

CONCLUSION

The IGHG(bf-n) allele and homozygous IGHG2(-n/-n) genotypes are associated with the development of severe RSV LRTI.

Serum Gm allotype development during childhood

Gm allotypes are genetic variants of the immunoglobulin heavy G chains (IGHG) of IgG molecules, coded from chromosome 14q32, characterized by differences in amino acid epitopes of the constant heavy G chains and inherited in the Mendelian manner. Gm allotypes have influence on IgG subclass levels, and serum Gm allotype levels have been given for different Gm genotypes in adults. Four hundred and thirty healthy children, aged 1-15 years, were examined for serum Gm allotypes and IgG subclasses from the six most common Gm genotypes and different age groups were measured using competitive enzyme-linked immunosorbant assay and radial immunodiffusion methods. Quantities (in g/l) of G1m(a) and G1m(f) of IgG1, G2m(n) and G2m(-n) of IgG2 and G3m(g), and G3m(b) of IgG3 are given. Different maturation rates of the alternative Gm allotypes within IgG1, IgG2 and IgG3 were shown. G2m(n) development was strikingly retarded compared with G2m(-n) from the gamma2 locus. This was found comparing IgG2 levels from homozygous G2m(-n-n) and G2m(nn) individuals, but was also seen in heterozygous G2m(n-n) genotypes. From the gamma1 locus G1m(f) levels dominated significantly, but inconstantly, over G1m(a) levels in heterozygous G1m(af) individuals. In homozygous G1m genotypes, G1m(aa) compared with G1m(ff) of the same age, one or the other dominated, sometimes significantly. Serum levels of G3m(b) from the gamma3 locus of homozygous G3m(bb) individuals were increased significantly compared with G3m(g) levels of homozygous G3m(gg) individuals, in ages over 3 years. However, in heterozygous G3m(gb) individuals G3m(b) dominance was not evident. There is a relatively rapid development of G1m(f) molecules and a retarded development of G2m(n) in the Gm(f;n;b) haplotype. In comparison, G1m(a) is retarded and G2m(-n) is enhanced in the Gm(a;-n;g) haplotype. The retarded serum G2m(n) development is comparable with serum IgA development during childhood. Different maturation rates of Gm allotypes within the same IgG subclass provide further explanation for the variation of the antibody response during childhood. Quantitative Gm allotype determinations give information of the activity from IGHG genes. The genetic variation constitutes an additional basis for evaluation of IgG antibodies in different diseases in childhood.

Preparation of IgG subclass allotypes from polyclonal IgG

Two allotypes have been identified for each of the IgG subclasses IgG1, IgG2 and IgG3. These allotypes are referred to as G1m(a) and G1m(f), G2m(n) and G2m(-n), and G3m(g) and G3m(b). Using a pool of normal human serum and a combination of preparative electrophoresis, DEAE ion-exchange and protein A-Sepharose chromatography, it was possible to separate G1m(f) from G1m(a), G2m(-n) from G2m(n) and G3m(g) from G3m(b). Purification of G2m(-n) molecules is of special interest as no genetic marker has been found to identify this allotype.

Immunoglobulin allotypes (GM and KM) and their interactions with HLA antigens in autoimmune diseases: a review

GM and KM immunoglobulin (Ig) allotypes and their interactions with HLA antigens have been analyzed in various autoimmune diseases: multiple sclerosis, rheumatoid arthritis, insulin-dependent diabetes mellitus (IDDM), systemic lupus erythematosus, coeliac disease, Crohn's disease, Graves' disease, atrophic thyroiditis, Hashimoto's thyroiditis, myasthenia gravis, chronic active hepatitis, alopecia areata, uveitis, vitiligo, Turner's syndrome, glomerular nephritis, Berger's disease and idiopathic dilated cardiomyopathy. This review reports published results about associations or linkages, as well as the origins of the populations, the numbers of patients and controls tested. The possible role of Ig polymorphisms in the physiopathology of autoimmune diseases is discussed. Ig allotypes and statistical methods used to analyse the HLA and Ig data are also described.