HLA (Human Leucocyte A) system

a major HISTOCOMPATABILITY complex of four genes (perhaps five) called HLA-A, HLA-B, HLA-C and HLA-D, with the D locus nearest to the centromere on the shorter arm of chromosome 6. Each gene has up to 35 alleles, the particular combination of alleles of the four genes on a chromosome being called the haplotype. Since humans are diploid organisms we have two haplotypes, these being determined by testing the individual's white blood cells for the specific HLA antigens.

Although these large numbers of alleles would appear to make the system a complex one in terms of possible combinations in each individual, in fact the situation is simpler than it seems. The four loci within the HLA system are so tightly linked together that there is very little CROSSING OVER between them. Thus each haplotype tends to be passed onto an offspring as a block rather than as four individual genes. Given no recombination between the four genes, four rearrangements would be expected to occur in the progeny of a mating. Thus any child of a cross has a one-in-four chance of inheriting precisely the same HLA combination as another sibling. Since the success of organ transplantation depends upon a close match of HLA alleles (even one allele difference can cause the foreign organ to be rejected), the chance of matching HLA types is highest within closely related individuals.

Collins Dictionary of Biology, 3rd ed. © W. G. Hale, V. A. Saunders, J. P. Margham 2005

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References in periodicals archive

Issues of cost, numbers of samples processed, and simplicity are all relevant and important, but the satisfaction of certain metrics is the top priority because of the ever-evolving complexity of the HLA system. These key metrics, including sample, locus, and allele balance as well as uniformity of coverage, are described in the Analytic Systems section below.

Targeted Next-Generation Sequencing for Human Leukocyte Antigen Typing in a Clinical Laboratory: Metrics of Relevance and Considerations for Its Successful Implementation

HLA system) and those that are specific to platelets, such as the human platelet antigen (HPA) system.

Absolute platelet refractoriness associated with HLA antibodies: A case report

Thus the autoimmune mechanisms involving the HLA system may provide connections between PsA and Dupuytren's disease.

An intractable case of suspected psoriatic arthritis combined with Dupuytren's disease

Forensics started advancing with advancements in the field of genetics where HLA system and Restriction Fragment Length Polymorphisms (RFLPs) opened new ways for investigation.

Forensic science past present and future

MHC molecules in human beings are known as human leukocyte antigens (HLA) or the HLA system (PEAKMAN; VERGANI, 1999).

Discrepancies in HLA typing: use of different methods to confirm doubtful or inconclusive results/Discrepancias na tipagem HLA: diferentes metodos para confirmar resultados duvidosos ou inconclusivos

Basanta, "Association of dengue hemorrhagic fever with the HLA system," Haematologia, vol.

HLA-B*44 is associated with dengue severity caused by DENV-3 in a Brazilian population

Among the antigens of HLA system HLAA3, HLA-B8, HLA-Cw6 prevailed; group II (36 patients) were characterized by eruptions in the area of large skin folds (intertrigo-like form), among which the immunologic disorders and significant increase in TNF-alpha were most important.

The causes of clinical polymorphism in psoriasis

The HLA system: immunobiology, HLA typing, antibody screening and crossmatching techniques.

Luminex-based virtual crossmatching for renal transplantation in South Africa