Human Platelet Antigens Nomenclature

Historically, multiple names existed for the human platelet antigens. In 1990, the Platelet Serology Working Party of the International Society of Blood Transfusion

(ISBT) and the International Committee for Standardization in Haematology (ICSH) suggested a numerical terminology which has been widely accepted.[1] The term HPA was introduced to indicate human platelet antigen. By convention, ''system'' is assigned to an HPA where both SNP and alloantibodies have been identified. The different antigens are numbered in the order of their discovery. The high-frequency allele of a system is named first (=a) and its low-frequency allele second (=b). The ''W'' after the antigen name is added when alloantibodies for only one allele have been defined. Six biallelic alloantigen systems (HPA-1 to -5 and HPA-15) and the low-frequency antigens HPA-6W to HPA-16W have been described. Table 1 lists HPA types, previous designations, associated nucleotide and amino acid changes, the frequency of each antigen in Caucasians, and the corresponding glycoproteins. Phenotype frequency varies significantly within populations. The Platelet Nomenclature Committee of the ISBT and the International Society of Thrombosis and Haemostasis (ISTH) developed, in 2003, a new nomenclature system.[3] The Platelet Nomenclature Committee maintains a web site with the latest changes, as well as with the positions for the newly assigned single nucleotide polymorphisms.[3]

Most platelet alloantigenic determinants characterized so far were formed by single amino acid substitutions induced by a point mutation of the respective gene. One exception is the rare platelet alloantigen HPA-14W which was formed by one amino acid deletion (Lys611del) of platelet GPIIIa (Table 1).

Some of the ''platelet-specific'' antigens have been detected on other cells as well. Therefore antigens are now called ''platelet associated'' and are divided into two groups: ''platelet-nonspecific'' antigens which are shared by platelets and many diverse cell types, and the ''platelet-specific'' antigens which are uniquely expressed by platelets.

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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