HLA Testing & Typing

The human major histocompatibility complex (MHC), or human leukocyte antigen (HLA) complex, comprises several genetic loci on the short arm of chromosome 6. Seven of these loci encode two distinct classes of highly polymorphic cell surface antigens. Class I MHC antigens include HLA-A, HLA-B, and HLA-C, each encoded by a separate locus. Class II MHC molecules include HLA-DR, HLA-DQ, and HLA-DP each having varying degrees of alloimmunity.

Many alleles exist for each locus of the Class I and Class II of HLA genes. An extensive sequence polymorphism is present in the second exon of Class II loci and in the second and third exons of Class I loci. These polymorphic regions encode the peptide-binding groove of the MHC molecule and are important to disease susceptibility and transplantation. KCL uses the Sequence-Based Typing (SBT) methods, including Next Generation Sequencing (NGS) and Sanger Sequencing, to determine HLA-A, B, C and HLA-DR, DQ, DP high-resolution type for haematopoietic stem cell patients and their selected unrelated donors. In addition, HLA alleles have been implicated in susceptibility or resistance to a variety of autoimmune, infectious, and oncologic disorders. HLA association studies must use typing techniques with high resolution that distinguish the HLA subtypes.

Significant associations have been found between the HLA alleles and certain disorders or deficiencies in many disciplines, including rheumatology, nephrology, neurology, endocrinology, gastroenterology, respiratory, ophthalmology, infectious disease, dermatology, immunology and psychology. SBT helps define the possible associated HLA subtypes and is of interest for R & D projects concerned with T cell mediated immune response. Determination of the individual HLA marker is often used diagnostically in immunotherapy and immunomodulation approaches.