Gene deletion and gene duplication within the cluster of human heavy-chain genes. Selective absence of IgG sub-classes.
Individuals with selective absence of IgG1 and IgG2 were discovered by testing for allotypes and isotypes of the respective sub-classes. These individuals were homozygous for sub-class deleted Gm-Am haplotypes, as shown by allotype studies in two families (Gm--;..;g;A2m1/Gm--;n;b;A2m1 and Gm--;n;b;A2m1/Gm--;..;b;A2m1) and by a population study of New Guineans (Gm fa;--;b;A2m2). The individuals with IgG1 sub-class deficiency showed elevation of IgG2, IgG4 and in particular of IgG3. Gene deletion can result from unequal crossing over which renders a complementary chromosome with a duplication of a sub-class gene. In one family, duplication of gamma 3 genes was observed to have happened in one of a twin pair. Quanitation of sub-classes in families with gamma 1- and with gamma 3-duplicated haplotypes did not show increased levels of the gene involved.
D003434:Crossing Over, Genetic; D005006:Ethnicity; D005260:Female; D006801:Humans; D017099:IgG Deficiency; D007126:Immunoglobulin Allotypes / Q000235:genetics; D007074:Immunoglobulin G / Q000235:genetics*; D007143:Immunoglobulin Heavy Chains / Q000235:genetics*; D007153:Immunologic Deficiency Syndromes / Q000235:genetics; D008297:Male; D010375:Pedigree; D011995:Recombination, Genetic
D007126:Immunoglobulin Allotypes; D007074:Immunoglobulin G; D007143:Immunoglobulin Heavy Chains