title: [Analysis for 2 samples with HLA-DQB1 allele dropout at exon 2 in sequence-based typing].
abstract: OBJECTIVE
  To explore the reason for HLA-DQB1 allele dropout during routine sequence-based typing(SBT) in order to improve the accuracy of typing.
  
  
  METHODS
  Two thousand samples derived from HLA high-resolution typing laboratory were typed for HLA-DQB1 locus using an AlleleSEQR HLA-DQB1 SBT kit. Non-conclusive results and "abnormal" sequencing samples were retyped using a LABType rSSO HD HLA-DQB1 kit and further analyzed with both sequence-specific primers and group-specific primers and sequenced for haplotype analysis.
  
  
  RESULTS
  Among the 2000 samples, 2 samples with no conclusive result were identified. The heterozygosity was confirmed with both the LAB Type SSO HD HLA-DQB1 kit and PCR-SBT in house method. Subsequent HLA-DQB1 cloning and haplotype sequencing have elucidated that HLA-DQB1*02:02 dropped out at exon 2 for the first sample and HLA-DQB1*02:01:01 dropped out at exon 2 for the second sample during PCR amplification. No novel nucleotide mutation was found.
  
  
  CONCLUSIONS
  Our results indicated that preferential amplification at exon 2 of DQB1 may result in allele dropout in exon 2 sequences during HLA-DQB1 SBT test. This may provide useful information for HLA genotyping.
authors.affiliation: Shenzhen Blood Center, Shenzhen Key Laboratory of Histocompatibility and Immunogenetics, Shenzhen, Guangdong 518035, P.R. China. zhihui_deng@yahoo.sina.cn.
authors.forename: Suqing
authors.initials: S
authors.lastname: Gao
authors.forename: Daming
authors.initials: D
authors.lastname: Wang
authors.forename: Yunping
authors.initials: Y
authors.lastname: Xu
authors.forename: Zhihui
authors.initials: Z
authors.lastname: Deng
mesh_terms: D000483:Alleles; D017931:DNA Primers / Q000235:genetics; D005091:Exons; D005838:Genotype; D059866:HLA-DQ beta-Chains / Q000235:genetics*; D006650:Histocompatibility Testing / Q000379:methods*; D006801:Humans; D016133:Polymerase Chain Reaction / Q000379:methods*
chemical_list: D017931:DNA Primers; D059866:HLA-DQ beta-Chains; C069051:HLA-DQB1 antigen