Genetic B‐Cell Variation Based on Immunoglobulin Heavy G‐Chain (Gm) Genes

• Published in: Scandinavian journal of immunology 1999-04, Vol.49 (4), p.345-346
• Main Author: Oxelius, V A
• Format: Article
• Language: English
• Subjects: B-Lymphocytes - immunology; B-Lymphocytes - metabolism; Genes, Immunoglobulin; Genetic Variation - immunology; Humans; Immunoglobulin Gm Allotypes - genetics
• ISSN: 0300-9475; 1365-3083
• DOI: 10.1046/j.1365-3083.1999.00520.x

Immunoglobulins are unique products of B cells. The different phases of B-cell development have been studied extensively. Variability in B cells based on the genetic variation of immunoglobulin heavy G-chain (IGHG) genes, could be suggested. The IGHG genes on chromosome 14q32 can be easily studied by the serum expression of Gm allotypes quantitatively. Gm allotypes are defined by minor amino acid epitope differences in the heavy constant chain of the IgG1, IgG2 and IgG3 molecules, and are inherited in the Mendelian way. The IGHG3, IGHG1 and IGHG2 genes, the order in which they appear on the chromosome, are characterized by two Gm allotypes from two alternatives on every IgG subclass locus. The alternative Gm allotypes are: for IgG3, G3m(g) and G3m(b); for IgG1, G1m(a) and G1m(f); and for IgG2, G2 m(n) and G2m(-n). Four variants of IGHG genes are known according to Gm haplotypes namely: 1/Gm(b,f,n), 2/Gm(b,f,-n), 3/Gm(g,a,n) and 4/Gm(g,a,-n). The variation in a Caucasian population is the combination of these four haplotypes found in 10 different genotypes some of which are common and others very rare. The different genotypes are found in the following proportions: Gm(b,f,n)/(b,f,n), 22.3%; Gm(b,f,n)/(b,f,-n), 20.4%; Gm(b,f,-n)/(b,f,-n), 7.0%; Gm(g,a,n)/(g,a,n), 1.3%; Gm(g,a,n)/g,a,-n), 0%; Gm(g,a,-n)/g,a,-n), 14%; Gm(g,a,n)/(b,f,n), 3.8%; Gm(g,a,n)(b,f,-n), 0%; Gm(g,a,-n)(b,f,n), 19.1%; and Gm(g,a,-n)/(b,f,-n), 12.1%.