Immunohaematology (Blood Transfusion) Dr. Dalia Galal

1.1 Historical Overview of Immunohematology Immunohematology is one of the specialized branches of medical science. It deals with the concepts and clinical techniques related to modern transfusion therapy. The era of blood transfusion, however, really began when William Harvey described the circulation of blood in 1616. Due to the many disastrous consequences resulting from blood transfusion, transfusions were prohibited. Blood transfusions continued to produce unpredictable results, until Karl Landsteiner discovered the ABO blood groups in 1900, which introduced the immunological era of blood transfusion.

History of Blood Groups and Blood Transfusions                       Experiments with blood transfusions have been carried out for hundreds of years. Many patients have died and it was not until 1901, when the Austrian Karl Landsteiner discovered human blood groups, that blood transfusions became safer. He found that mixing blood from two individuals can lead to blood clumping. The clumped RBCs can crack and cause toxic reactions. This can be fatal.  

History of Blood Groups and Blood Transfusions (Cont.) Karl Landsteiner discovered that blood clumping was an immunological reaction which occurs when the receiver of a blood transfusion has antibodies against the donor blood cells. Karl Landsteiner's work made it possible to determine blood types and thus paved the way for blood transfusions to be carried out safely. For this discovery he was awarded the Nobel Prize in Physiology or Medicine in 1930.

It became clear that the incompatibility of many transfusions was caused by the presence of certain factors on red cells now known as antigens (a substance that can stimulate an immune response). Two main postulates were also drawn by this scientific approach: 1. Each species of animal or human has certain factor on the red cell that is unique to that species. 2. Even each species has some common and some uncommon factor to each other. This initiated the era of scientific – based transfusion therapy and was the foundation of immunohematology as a science

What is blood made up of?                        An adult human has about 4–6 liters of blood circulating in the body. Blood consists of several types of cells floating around in a fluid called plasma. The red blood cells (RBCs) contain haemoglobin, a protein that binds oxygen. RBCs transport oxygen to, and remove carbon dioxide from the tissues. The white blood cells fight infection. The platelets help the blood to clot, if you get a wound for example. The plasma contains salts and various kinds of proteins.  

What are the different blood groups? Blood Groups, Blood Typing and Blood Transfusions The discovery of blood groups                       Experiments with blood transfusions, the transfer of blood or blood components into a person's blood stream, have been carried out for hundreds of years. Many patients have died and it was not until 1901, when the Austrian Karl Landsteiner discovered human blood groups, that blood transfusions became safer. Mixing blood from two individuals can lead to blood clumping or agglutination. The clumped red cells can crack and cause toxic reactions. This can have fatal consequences. Karl Landsteiner discovered that blood clumping was an immunological reaction which occurs when the receiver of a blood transfusion has antibodies against the donor blood cells. Karl Landsteiner's work made it possible to determine blood types and thus paved the way for blood transfusions to be carried out safely. For this discovery he was awarded the Nobel Prize in Physiology or Medicine in 1930.                                                                                               Blood group 0 If you belong to the blood group 0 (null), you have neither A or B antigens on the surface of your red blood cells but you have both A and B antibodies in your blood plasma. What are the different blood groups? The differences in human blood are due to the presence or absence of certain protein molecules called antigens and antibodies. The antigens are located on the surface of the RBCs and the antibodies are in the blood plasma. Individuals have different types and combinations of these molecules.   The blood group you belong to depends on what you have inherited from your parents.

Red Cell membrane structure Surface of the RBC consists of a bilipid membrane in which large protein molecules are embedded. Composed of phosholipids which are both hydrophilic (heads) and hydrophobic (tails).

Red Blood Cell Membrane

Red Blood Cell Membrane External surface of RBC membrane is coated with a diverse array of glycoproteins, complex carbohydrates, and lipoproteins, imparting antigenic structure to the membrane.

Major blood group systems

What are the different blood groups? There are more than 20 genetically determined blood group systems known today The AB0 and Rhesus (Rh) systems are the most important ones used for blood transfusions. Not all blood groups are compatible with each other. Mixing incompatible blood groups leads to blood clumping or agglutination, which is dangerous for individuals.

The Blood Group Systems Inheritance and Genetics

Glossary • Gene • Locus • Allele • Heterozygous • Homozygous • Phenotype • Genotype • Sex Chromosome • Autosomal Chromosome • Dominant Gene • Recessive Gene

Chromosomes Gene Locus Heterozygous Chromosome is a single piece of coiled DNA that contain thousands of genes. Gene • A section of DNA made of bases that code for a phenotype. Example: eye colour • Each gene has a coding“ sequences that determine the production of certain protein in our body. (eg, blood antigens are determined by different genes) Locus Location of a gene on a chromosome • Allele Variation of a gene that produces an alternative Phenotype Heterozygous 2 identical chromosomes with DIFFERENT Gene types i.e. Dominant & Recessive Homozygous 2 identical chromosomes with the SAME genes on each chromosome ie Dominant & Dominant

• Sex Linked Chromosome Is either X or Y. Determines gender. Females have XX, males have XY Autosomal Chromosome Pairs of chromosomes that have identical gene location, and are the same in Male and Females. Only the code within the gene varies Dominant Gene A strong gene that only needs one copy on one chromosome to be expressed. Recessive gene Weak gene that needs a copy on each autosomal chromosome (M&F), or on each XX in women, or on the X in men, to be expressed Genotype and phenotype: The genetic composition from a particular inherited characteristic is called the genotype and the way this can be seen is called phenotype. Thus if a person is group A (genotype) his phenotype could be either AA or AO.