Dr. Abbas Alsaeed
Contents (CLS 441)
1. Introduction of Immunohaematology
2. ABO Blood Group System
3. The Rh Blood Group System
4. Other Blood Group System
5. Antihuman Globulin (Coombs’) Test
6. Detection and Identification of Antibodies
7. Cross Matching (Compatibility Testing)
8. Transfusion Reactions and Complications
9. Screening for Diseases Transmitted
10. The Blood Donor and Collection of Blood
11. Storage and Preservation of
Blood and Components
12. Haemolytic Disease of the Newborn (HDN)
13. Autoimmune Haemolytic Anaemia (AIHA)
14. Blood Components
15. Transfusion Therapy
The immune system has evolved as a highly specialized function of human beings and is concerned with the substances considered “foreign” to the body.
It consists of a cellular component and a humoral component. Although the field of blood group serology is associated mainly with the humoral component of the immune system, the mechanics of antibody production in vivo involves the cellular arm of the immune system or the cell mediated immunity.
The science of immunohaematology deals with the basic principles of antigen and antibody structure, the genetics, the biochemistry, its mode of action and it’s role in haematology.
To understand the principles of compatibility testing and transfusion reactions the basic knowledge of immunohaematology is essential.
Antigen is a substance which elicits immune response.
It is a complex molecule whose molecular weight exceed 10000, daltons. The ABH antigens are glycolipids while Rh antigen is a protein. The HbsAg is a lipoprotein.
A number of characteristics influence the antigenicity. These include the molecular size, charge and the solubility. The inheritance of Ir genes and occurrence of disease also influence the antibody response. All the blood group substances are not equally immunogenic. Approximately 50 percent of Rh negative recipients of Rh positive blood are expected to be sensitized to the D antigen. Other Rh antigens like C and E and other blood group systems are much less immunogenic. That is the reason that only D and not other Rh antigens are routinely typed in the blood bank. The number of antigen sites on the RBC vary according to specificity. There are approximately 1 million ABO antigen sites and 25000 Rh (D) antigen sites on RBC.
Some of the specificities are poorly developed at the time of birth.
The antibodies are immunoglobulin in nature. Approximately, 82-96 percent of antibodies are polypeptide and the rest 4-18 percent are carbohydrates.
Production of antibody
The antibodies are produced in the circulation of those individuals who lack that particular antigen. The production may be as a result of either blood transfusion or Foeto-maternal leak of incompatible blood.
All immunoglobulin share a common chemical structural configuration. Each basic antibody unit is composed of four polypeptide chains: two identical light chains (M.W approximately 22500 daltons) and two identical heavy chains (M.W approximately 50000-75000 daltons). The four chains are held together by covalent disulfide bonds. Each heavy chain has 440 amino acids and each light chain 220 amino acids.
The chemical structure of heavy chains is responsible for the diversity of immunoglobulin classes while the light chains are kappa and lambda common to all immunoglobulins.
The isotypes of the heavy chains determine the class of immunoglobulin. There are basically five class of immunoglobulins designated as IgA, IgD, IgE, IgG and IgM. The blood group antibodies are usually, IgM, IgG or IgA.
IgA class of antibodies exist both as monomer and polymers. The M.W is approximately 160000 daltons....