HLA typing in organ transplant part 12

Tissue typing by molecular method, utilizing the sequence-specific oligonucleotide and sequence-specific primer technologies has been in routine use in many-typing laboratories worldwide for more than 20 years since the development of the polymerase chain reaction. Both methods are very useful for clinical and research purposes and can provide generic (low resolution) to allelic (high resolution) typing results. DNA based methods had more sensitivity, accuracy and resolving power than serologic typing methods. Sequencing-based typing  is a high resolution method for the identification of HLA polymorphysms. The majority of HLA Class I alleles can be discriminated by their exon 2 and 3 sequence, and for Class II alleles, exon 2 is generally sufficient. There are polymorphic positions in other exons, which may require additional sequencing to exclude certain alleles with differences outside exon 2 and 3, depending on the clinical requirements and relevant accreditation guidelines. Examination of all nucleotides, both at conserved and polymorphic positions enables the direct identification of new alleles, which may not be possible with techniques such as sequence-specific oligonucleotide and sequence-specific primer typing.