Km genotyping using polymerase chain reaction-allele specific oligonucleotide in Koreans

The allotype of human immunoglobulin kappa light chain constant region gene (IGKC) has been identified by the serological assay or DNA typing method. The three allotypes Km*1, Km*1,2 and Km*3 have amino acid substitutions at positions of codons 153 and 191 in the kappa light chain constant region. The Km allotypes were designated as follows: Km*1 has valine (GTC) at position 153 and leucine (CTC) at 191; Km*1,2 has Ala153 (GCC) and Leu191 (CTC); Km*3 has Ala153 (GCC) and Val191 (GTC). In this study, polymerase chain reaction-allele specific oligonucleotide (PCR-ASO) was used to provide a specific allelic typing system for the IGKC gene in 213 unrelated Koreans. For Km genotyping, the IGKC coding regions plus 35 bp of the 3' untranslated regions were amplified with specific primers. Amplified genes were hybridized with Km ASO probes at positions of codons 153 and 191 and were detected using a colorimetric detection method. The frequencies of Km*1,2/Km*1,2, Km*1,2/Km*3, and Km*3/Km*3 were 17.8% (n=38), 51.7% (n=110), and 30.5% (n=65), respectively. The estimated allele frequencies for Km*1,2 and Km*3 were 0.44 and 0.56, respectively. The homozygote or the heterozygote of Km*1 was not observed in this study. The PCR-ASO method distinguished the alleles Km*3, Km*1,2, and Km*1 and also distinguished the homozygote from heterozygote. Km frequencies vary significantly among various populations. Km*3 in Koreans was very similar to those observed in northern Chinese, Japanese, and the native people of British Columbia. It was lower than that reported in Caucasian, Indian, or southern Chinese.