Generation of the B*41 group of alleles as indicated by intron sequences.

The generation of the B41 alleles has been analysed using exon 1, intron 1, exon 2, intron 2 and exon 3 sequences. Results showed that B4102 may have been generated as the first B41 allele by a recombination mechanism between B400102 and B0801 or B4201 involving intron 2. B4101, B4104 and B4107 alleles could have been generated from B4102 by a gene conversion event taking three different fragments from sequences belonging to intron 2/exon 3 of B45, B50 or B49 alleles. B4105 and B4106 could be generated from B4101 allele by point mutations, and B*4103 generation is unclear due to the lack of intron 2. The importance of introns in HLA-B allele polymorphism generation is stressed.