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Citing this page: Lefranc, M.-P. and Lefranc, G. Human Gm, Km and Am allotypes and their molecular characterization: a remarkable demonstration of polymorphism In: B. Tait, F. Christiansen (Eds.), Immunogenetics, chap. 34, Humana Press, Springer, New York, USA. Methods Mol. Biol. 2012; 882, 635-680. PMID: 22665258

Part 1 - Gm allotypes and Gm haplotypes

Allotypes have been identified for five of the human IGHC genes, the IGHG1, IGHG2, IGHG3, IGHA2 and IGHE genes, and are designated as G1m, G2m, G3m, A2m, and Em allotypes, respectively. These allotypes are inherited in fixed combinations, or Gm-Am-Em haplotypes.

Overview

Gm polymorphism is determined by the IGHG1, IGHG2 and IGHG3 genes which have alleles encoding allotypic antigenic determinants referred to as G1m, G2m, and G3m allotypes for markers of the human IgG1, IgG2 and IgG3 molecules (no Gm allotypes have been found on the gamma 4 chain) (for review see [1]). At present, 18 Gm allotypes are known: G1m (1, 2, 3, 17) or G1m (a, x, f, z), G2m (23) or G2m (n), G3m (5, 6, 10, 11, 13, 14, 15, 16, 21, 24, 26, 27, 28) or G3m (b1, c3, b5, b0, b3, b4, s, t, g1, c5, u, v, g5) [2].
The allotypes are inherited in fixed combinations called Gm haplotypes [3-5]. The Gm haplotypes are powerful tools for the characterization of different populations [6-12].

Nomenclature of the Gm allotypes and haplotypes

Citing this table: Lefranc, G. et al., 1982 [3], 1983 [4].

Populations
(see Part 2)		 Gm haplotypes
Numerical designation (1) Previous alphabetical designation (1)
Simplified form (2,3) Complete description (3) Simplified form (2,3) Complete description (3)
Caucasoids Gm 5*;3;..
Gm 5*;3;23		 Gm 5,10,11,13,14,26,27;3;..
Gm 5,10,11,13,14, 26,27;3;23		 Gm b*;f;..
Gm b*;f;n		 Gm b0,b1,b3,b4,b5,u,v;f;..
Gm b0,b1,b3,b4,b5,u,v;f;n
Caucasoids and Mongoloids Gm 21*;1,17;..
Gm 21*;1,2,17;..		 Gm 21,26,27,28;1,17;..
Gm 21,26,27,28;1,2,17;..		 Gm g*;z,a;..
Gm g*;z,a,x;..		 Gm g1,g5,u,v;z,a;..
Gm g1,g5,u,v;z,a,x;..
Negroids Gm 5*;1,17;..
Gm 6,24*;1,17;..
Gm 6*;1,17;..
Gm 15*;1,17;..		 Gm 5,10,11,13,14,26,27;1,17;..
Gm 5,6,11,24,26;1,17;..
Gm 5,6,10,11,14,26,27;1,17;..
Gm 10,11,13,15,27;1,17;..		 Gm b*;z,a;..
-
-
-		 Gm b0,b1,b3,b4,b5,u,v;z,a;..
Gm b0,b1,c3,c5,u;z,a;..
Gm b0,b1,b4,b5,c3,u,v;z,a;..
Gm b0,b3,b5,s,v;z,a;..
Mongoloids Gm 15,16*;1,17;..
Gm 5*;1,3;..
Gm 5*;1,3;23		 Gm 10,11,13,15,16,27;1,17;..
Gm 5,10,11,13,14,26,27;1,3;..
Gm 5,10,11,13,14,26,27;1,3;23		 Gm st*;z,a;..
Gm b*;f,a;..
Gm b*;f,a;n		 Gm b0,b3,b5,s,t,v;z,a;..
Gm b0,b1,b3,b4,b5,u,v;f,a;..
Gm b0,b1,b3,b4,b5,u,v;f,a;n

Location of the Gm allotypes and prevalent Gm haplotypes

Citing this figure: Lefranc G. et al. 1982 [3], 1983 [4].

location

The allotypes are located on CH domains encoded by the respective IGHG CH exons.

IMGT notes:
(1) The nomenclature of the Gm allotypes (numerical designation) is according to the recommendations of WHO nomenclature 13,14]. G2m (23) is the only allotype presently defined on the gamma 2 heavy chains; two dots are used to indicate the absence of this allotype on the gamma 2 chains.
(2) For convenience, the most common G3m haplotypes can be written in a simplified form, a dash indicates that there is no frequently simplified form:
5* for G3m5,10,11,13,14,26,27 b* for b0,b1,b3,b4,b5,u,v
21* for G3m21,26,27,28 g* for g1,g5,u,v
15* for G3m10,11,13,15,27
15,16* for G3m10,11,13,15,16,27 st* for b0,b3,b5,s,t,v
6* for G3m5,6,10,11,14,26,27
6,24* for G3m5,6,11,24,26
(3) The nomenclature of the Gm haplotypes takes into account the IGHG gene order in the locus. The Gm allotypic markers of the gamma 1, gamma 2, and gamma 3 chains are written in the linkage order of the subclass genes, i.e., G3, G1, and G2, with semicolons separating the subclasses and comas separating the allotypic markers.
References:
[1] Lefranc, M.-P. and Lefranc, G., In: Shakib F (ed) The human IgG subclasses: molecular analysis of structure, function and regulation. Pergamon, Oxford, pp. 43-78 (1990).
[2] Lefranc, G. et al., Hum. Genet., 50, 199-211 (1979).
[3] Lefranc, G. et al., J. Immunogenet., 9, 1-9 (1982).
[4] Lefranc, G. et al., Eur. J. Immunol., 13, 240-244 (1983).
[5] Schanfield, M.S. and Loghem, E. van, In: Weir, D.M. et al (eds), Handbook of Experimental Immunology, 4th edn. Edinburg Blackwell Scientific, Blackwell, chapter 94, pp. 1-18 (1985).
[6] Lefranc, G. et al., Acta Anthropogenetica, 1, 34-45 (1976) pdf
When citing this paper, please add also the following information: on-line at IMGT, the international ImMunoGeneTics information system®, http://www.imgt.org (IMGT Repertoire>Allotypes>IGHC>Human>Part 1 and Part 2)
[7] Lefranc, G. et al., Am. J. Hum. Genet., 28, 51-61 (1976).
[8] Gershowitz, H. and Neel, J.V., Am. J. Phys. Anthropol., 49, 289-301 (1978).
[9] Lefranc G. et al., Hum. Genet., 41, 197-209 (1978).
[10] Lefranc, G. et al., Hum. Genet., 50, 199-211 (1979).
[11] Steinberg, A.G. and Cook, C.E. The distribution of the human immunoglobulin allotypes. Oxford University Press, Oxford (1981).
[12] Zhao, T. and Lee, T.D., Hum. Genet., 83, 101-110 (1989).
[13] WHO. Meeting on human immunoglobulin allotypic markers, J. Immunogenet., 3, 357-362 (1976).
[14] Ghanem, N. et al., Eur. J. Immunol., 18, 1067-1072 (1988).