The antigenic determinants of the erythrocyte blood group systems are inherited, usually, following the dictates of formal genetics. During cell division (Mitosis), chromatin loses its homogeneous structure and the chromosomes in which the units of genetic information are present, called genes. The genes are distributed with a specific order along the chromosome, in a precise physical location called the locus. Alternative forms of genes, each of which can occupy a single locus on one of the homologous chromosomes, are termed alleles.

The ISBT terminology distinguishes between the alleles for blood group antigens and the antigens that they encode. For example, the major antigens of the ABO system are A, B, and O, yet the alleles are A, B, and O. In the Kell system, two alleles, K and k, determine the K and k antigens, respectively. In other cases, the name of the gene alleles is very different from that of the antigens they determine. For example, in the MNSs blood group system, the genes are named GYPA and GYPB. Almost all the gene alleles coding for the antigens of the erythrocyte blood group systems are in one of the 22 pairs of autosomes, only one allele coding for the Xg and Xk antigens has been located on the X chromosome.

Individuals who have identical alleles at a given locus on both chromosomes (i.e., K/K) are homozygous. In heterozygous condition, alleles present at the locus on each chromo some are nonidentical (i.e., K/k). Individuals who are homozygous for an allele, in some blood group systems, may have more antigen expressed on their red cells than persons who are heterozygous. For example, red cells from a person whose phenotype is Jk(a+b–) have a “double dose” of the Jka allele and, as a result, express more Jka antigen on the red cell surface than an individual whose phenotype is Jk(a+b+). The difference in amount of antigen expressed on the red cell membrane between a homozygous and a heterozygous phenotype sometime can be detected serologically (dosage effect).

Usually blood group antigens are expressed as codominant characters. Therefore, heterozygotes express the product of both alleles. For example, if an individual’s erythrocytes are typed as K + and k +, a K/k genotype can be inferred.

In ABO system, the situation is more complicated. In fact, the genes of the ABO system do not code for membrane proteins, but control the production of enzymes: glycosyltransferases. These enzymes add sugars to a preexisting oligo-carbohydrate chain, modifying it and giving it the antigenic specificity A or B or leaving it unchanged (O). The antigens of the ABO system are therefore oligosaccharide chains. The determinants of the other erythrocyte blood group systems are usually the glycoproteins present on the erythrocyte membrane of which they are often integral constituents (intrinsic proteins).

Effectiveness of an antigen in evoking the immune response is due to numerous characteristics, the total effect of which is defined as immunogenicity. Some of these characteristics are the exposure of the antigen and the number of determinants present on the erythrocyte membrane, maturation of the antigen during fetal life, its spread in the population, and more. Some relevant data concerning blood groups antigens are reported in Table 1.

Table1. Blood group systems with gene denomination and chromosome location

اخر الاخبار

اخبار العتبة العباسية المقدسة

أهالي كربلاء يحيون اليوم السابع لذكرى شهادة الإمام الحسين (عليه السلام)

مشروع أمير القراء الوطني يشهد مشاركة أكثر من 100 طالبٍ في مرحلته الثالثة

قسم الشؤون الفكرية يصدر دليلًا يوثّق القصص الفائزة في مسابقة فتوى الدفاع المقدسة

قسم الشؤون الفكرية يعلن عن توفير عددٍ من المكتبات الإلكترونية المتخصّصة للمؤسّسات الدينية والمكتبات العامّة

المزيد

الآخبار الصحية

نصائح عملية للحد من التعرق المفرط في الصيف

أطباء يحذرون: مكمل غذائي شائع قد يدمر الجهاز العصبي

تحذير طبي من تأثير جانبي "غير متوقع" لحقن التخسيس

حمامات الثلج قد تكون خطيرة وأحيانا مميتة.. ما السبب؟

المزيد

الآخبار التكنلوجية

أكبر جدارية شمسية في العالم تدخل موسوعة غينيس.. مشروع ضخم

تسارع دوران الأرض يثير القلق.. وتحذيرات من "كوارث محتملة" ؟

"سوذبيز" تطرح أكبر قطعة من المريخ على الأرض في مزاد علني

أوبن أيه آي تعتزم إطلاق متصفح إنترنت يعمل بالذكاء الاصطناعي

المزيد

مواضيع ذات صلة

Evaluation of Platelet Function In Vitro with PFA-100

Platelet Alterations

microalbumin (MA)

methylated septin 9 DNA (mSEPT9, ColoVantage)

methemoglobin (Hemoglobin M)

metanephrine, plasma free (Fractionated metanephrines)

measles rubeola antibody

maternal screen testing (Maternal triple screen, Maternal quadruple screen)

C-Reactive Protein Rapid Latex Agglutination Test

Hyporegenerative Macrocytic Anemias/ Megaloblastic Anemias

Unstable Hemoglobins

Glucose-6-Phosphate Dehydrogenase (G6PD) Deficiency