Tissue compatibility is determined by genes of the major histocompatibility complex, known as the human leukocyte antigen (HLA) system in humans. The HLA region comprises 12 genes that are characterized by an extensive degree of polymorphism. Initially detected by serology, HLA diversity has been found by molecular typing techniques to be much larger than anticipated, with over 1500 HLA alleles currently known and more to be disclosed. Three major polymerase chain reaction (PCR)-based methodologies are now used routinely for HLA genotyping: PCR sequence-specific primers (SSPs), PCR sequence-specific oligonucleotide probe (SSOP) hybridization, and direct sequencing of PCR products. The multigenic system, high heterozygosity rate, intralocus and interlocus sharing of sequence motifs, and the growing number of new alleles all make unambiguous HLA allelic assignments a complex issue in molecular diagnostics. The choice of the typing method will be influenced by the clinical setting, scaling of typing samples, emergency, and level of resolution required. Laboratories are facing several challenges: different clinical transplant programs call for different resolution levels, unambiguous allele assignments may require the use of more than one molecular technique, efficient quality assurance systems must be set up to control commercially available reagents, and updates should cope with newly identified HLA alleles.

Getting Started With Dumbbells

Getting Started With Dumbbells

The use of dumbbells gives you a much more comprehensive strengthening effect because the workout engages your stabilizer muscles, in addition to the muscle you may be pin-pointing. Without all of the belts and artificial stabilizers of a machine, you also engage your core muscles, which are your body's natural stabilizers.

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