HLA system

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Related to HLA system: human leukocyte antigen

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.

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.
Thus the autoimmune mechanisms involving the HLA system may provide connections between PsA and Dupuytren's disease.
Operational systems (also called "fielded systems") include those HLAs located at operational units, or remote HLA systems.
Antigens of HLA system, such as HLA-B8, HLA-B35, prevailed.
M, 2004, Gene and haplotype frecuencies of HLA system in the Norht-west Argentina.
the role of the HLA system in distinguishing self from non-self, and in eliminating diseased cells, and how this presents important biomarkers for diagnosis and therapy.
The HLA system uses a hydraulic pump/motor coupled to the drive shaft to both recoup braking energy when stopping and add power when starting or accelerating.
The critical role of HLA system in presenting peptides to antigen-specific T cell receptors may explain why only some women develop cervical cancer.
The HLA system is a group of antigens responsible for histocompatibility, that is, the acceptance or rejection of tissue transplants.
The HLA system is basically a blood group typing system," says Dr.