A specific switch alpha probe of the human immunoglobulin IGHA locus

New allele variants of the immunoglobulin switch (Salpha) regions

In this report we define ten Salpha1 IGHA1 (*S5-*S14) and nine Salpha2 IGHA2 (*S10-*S18) newly found alleles of the human immunoglobulin switch alpha 1 and switch alpha 2 regions, respectively, in Colombian Indian, Black and Mestizo populations, and a complete list of the SacI and PvuII alleles so far identified as given.

Molecular analysis of the T17 immunoglobulin CH multigene deletion (del A1-GP-G2-G4-E)

In the human, the order of the immunoglobulin heavy chain constant region (Ig CH) genes is the following: 5'-M-D-G3-G1-EP1-A1-GP-G2-G4-E-A2-3'. Extensive multigene deletions have been described in the Ig CH locus, some of these encompassing up to 160 kb. To date six different multigene deletion haplotypes have been identified, designated I to VI according to the chronological order of their being found: deletion I (del G1-EP1-A1-GP-G2-G4), II (del EP1-A1-GP), III (del A1-GP-G2-G4-E), IV (del EP1-A1-GP-G2-G4), V (del GP-G2-G4-E-A2), VI (del G1-EP1-A1-GP-G2). Individuals were found either homozygous for one type of deletion or heterozygous for two different deletions, mainly (17 cases out of 18) in the Mediterranean area. So far, deletions I and II have been found in Tunisia, deletions III, IV and V in Italy, and deletion VI in Sweden. In this paper, we show that a Tunisian, T17, previously reported as being homozygous for a deletion of type IV, is, in fact, homozygous for a deletion that encompasses A1-GP-G2-G4-E. Therefore T17 is the first case of a deletion of type III reported in the Tunisian population. Molecular analysis demonstrates that the T17 deletion occurred between highly homologous regions located downstream of IGHEP1 and IGHE, respectively. In contrast to the EZZ deletion, the recombination occurred near or in the switch regions, since the homologous regions involved in the deletion extend over 4.5 kb of DNA and encompass the I alpha 1-S alpha 1 and I alpha 2-S alpha 2 regions, respectively.

Genetic analysis of new restriction fragment length polymorphisms (RFLP) in the human IgH constant gene locus

The human immunoglobulin heavy chain constant gene locus (IGHC) is polymorphic at both the protein (Gm and A2m allotypes) and the DNA level [RFLP for the gamma genes (IGHG), the switch mu region (IGHSM) and the switch alpha regions (IGHSA)]. The polymorphisms have been a valuable tool for assessment of the IGHC locus organization and a variety of population genetics and immunological investigations. In this study three new probes, identifying regions related to the IGHG (IGHPG and IGHSG) or IGHA (IGHAT) genes, have been employed to describe 11 different loci, 6 of which were polymorphic. Most of the polymorphisms are probably due to short insertions/deletions, particularly the SG regions, due to their repetitive structure. Ten loci were assigned to the IGHC region on the basis of known restriction maps, deletion mapping and association with mapped RFLP; the 11th, despite a striking sequence similarity with the IGHPG regions, could not be assigned to any known IGHC subregion. Analysis of these and previously known IGHG RFLP in a sample of 65 unrelated subjects plus 15 families allowed us to draw a genetic map, with particularly high resolution in the GP-G2-G4 genes region, revealing a marked discontinuity in the linkage disequilibrium values between pairs of adjacent loci.