Sequencing based typing for genetic polymorphisms in exons 2, 3 and 4 of the MICA gene

We have established a sequencing based typing (SBT) method for detection of genetic polymorphism in the exon 2 to 4 domains of the major histocompatib ility complex (MWC) class I chain-related gene A (MICA) and applied it to a llele typing of 130 healthy Japanese individuals. A 2.2-kb segment includin g exons 2, 3 and 4 of the MICA gene was amplified by a pair of generic prim ers followed by cycle sequencing using exon-specific nested primers. In tot al, 8 alleles were observed in a Japanese population and the most frequent allele was MICA008 with the gene frequency of 30.8%. MICA009 was the second most frequent (16.5%), while the rarest one was MICA007 (1.2%). MICA allel es displayed strong linkage equilibria with HLA-B antigens (i.e. MICA008 wi th B7, B48, B60 and B61; MICA009 with B51 and B52; MICA002 with B35, B39, B 58 and B67; MICA004 with B44, MICA007 with B13 and B27; MICA010 with B46, B 62 and B48, MICA012 with B54, B55, B56 and B59; MICA019 and B70, B71 and B6 2). Recently the B48 haplotype has been reported to lack the entire MICA ge ne by a large-scale deletion in a Japanese population Among 8 serologically B48 homozygous individuals, 4 were found to represent this MICA null allel e as assessed by no polymerase chain reaction BCR) amplification using MICA -specific primers, while the remaining four possessed the intact MICA gene with MICA008 or MICA010.