7 ABO BLOOD GROUPING

1 HEMATOLOGY AND BLOOD BANK TECHNIQUEMODULEABO BLOOD GroupingHematology and BloodBank Technique 48 Notes7 ABO BLOOD INTRODUCTIONS everal BLOOD group systems have been described in humans. Of these, the ABOblood group system is most reading this lesson, you will be able to:zexplain commonly used terms in ABO groupingzdescribe antigen antibody reactionszdescribe the basis of ABO the techniques of ABO SOME COMMON ASPECTS OF IMMUNO-HEMATOLOGYWe will learn about some commonly used terms before beginning ABOgrouping. This will help in better understanding of the : An antigen is a substance usually a protein which when introduced intoan individual who recognizes it as foreign, leads to the production of antibody specifically reacts with the the red cell surface there is presence of glycoproteins and glycolipids whichact as antigens.

2 They are called BLOOD group antigens. These antigens can beon the surface, below or protrude from the red cell membrane. If introduced intothe body of an individual who lacks the antigen, an immune reaction can : These are immunoglobulins present in the serum and can be of 5types: IgG, IgM, IgD, IgA and IgE. 49 ABO BLOOD GroupingHEMATOLOGY AND BLOOD BANK TECHNIQUEMODULEH ematology and BloodBank TechniqueNotesIf red cells carrying an antigen are introduced into the circulation of an individualwho lacks that antigen, antibodies will form and cause destruction of theintroduced red cells . These are immune or acquired antibodies and are IgG innature. They react best at 37 antibodies occur without antigenic stimulus and are called naturallyoccurring antibodies ABO antibodies.

3 They are IgM in nature and reactat room QUESTIONS Substance leading to production of antibody is ..2.. & .. acts as Immunoglobulin of sera are ..4. Antibodies are .. present in Antibodies without antigenic stimulus is called as .. ANTIGEN ANTIBODY REACTIONSThe antigen antibody reactions relevant to BLOOD banking are:zsensitizationzagglutinationzhemolys iszneutralizationSensitization is the combination of antigen and antibody. This is a is the clumping of red cells . It occurs when sensitized cells comeinto contact with each other resulting in formation of bridges between them andformation of aggregates. It is the most common procedure in BLOOD as the name suggests is destruction of red cells resulting in the releaseof hemoglobin from the cells due to the action of complement.

4 This is used inantibody screening : BLOOD group antigens when added to serum containing antibodycan neutralize it. This is used in determining secretor status. If the strength ofthe antibody reduces, the antigen antibody reaction is assumed to have : This refers to the genes present on the chromosome inherited fromeach parent irrespective of whether they produce any product which AND BLOOD BANK TECHNIQUEMODULEABO BLOOD GroupingHematology and BloodBank Technique 50 NotesPhenotype: This is used to describe the observable effect of the inherited genesor expression of the genes the BLOOD QUESTIONS the following1. Sensitization(a) Observable effect of the inherited genes2. Agglutination(b) Destruction of red cells3.

5 Hemolysis(c) Genes on chromosome4. Genotype(d)Combination of antigen & antibody5. Phenotype(e) Clumping of red ABO BLOOD GROUP SYSTEMThe ABO GROUPING system is subdivided into 4 types based on the presence orabsence of antigens A and B on the red cell surface as shown below. Red cellsthat only have antigen A are called group A. Those that only have B antigen arecalled group B. cells that have both A and B antigens are group AB. cells thatlack both antigens are ANTIBODIESThe ABO antibodies ; anti-A and anti-B are naturally occurring antibodies andare present in the sera of individuals who lack the corresponding antigen. Cellswith A antigen will have anti-B in the serum. cells with B antigen will haveanti-A in the serum and cells with AB antigens will not have any O individuals will have both anti-A and anti-B antibodies.

6 Theseantibodies are IgM in antigens and the corresponding antibodies in each BLOOD group are and BNoneONoneAnti-A, Anti-B 51 ABO BLOOD GroupingHEMATOLOGY AND BLOOD BANK TECHNIQUEMODULEH ematology and BloodBank TechniqueNotesGenetics: All features in humans are controlled by genes present onchromosomes. Each cell has 23 pairs of chromosomes. There is one locus onchromosome 9 occupied by one of the three alleles A, B, O. The genes of theABO system are inherited as mendelian codominant. Each individual inheritsone gene from each parent. The chromosome from the mother carries one of A,Bor O gene. Similarly the chromosome from the father also has one of A, B orO gene. The gene on each chromosome determines the BLOOD group as shownbelow.

7 The A and B genes are dominant over the O AOGenotypeBlood group of childrenAAAAP henotypeMother group A, father group O and all children are group QUESTIONS the followingBlood GroupAntigen1. Group A(a) Has both A & B antigen2. Group B(b) Antigen A3. Group C(c) Lack of A & B antigen4. Group D(d) Antigen BTechnique of ABO GROUPING : Various techniques are available for ABOgrouping in the laboratory. These are1. Slide technique2. Tube technique3. Microplate technique4. Gel card techniqueSlide techniqueThis can be performed in emergency or outdoor camps but must not beperformed as a routine AND BLOOD BANK TECHNIQUEMODULEABO BLOOD GroupingHematology and BloodBank Technique 52 NotesMaterial required1.

8 Glass slides/white tile2. Monoclonal Antisera A and Antisera B3. Glass rod for mixing4. Marker penSample: BLOOD collected in a plain vial. Sample must be tested within should be kept in the refrigerator till processed. There should be no evidenceof hemolysis in the Mark one side of the glass slide as A and the other side as Put one drop of antisera A on the side marked as A and one drop of antiseraB on the side marked as Add one drop of test BLOOD sample/20% cell suspension to each Mix the BLOOD with the reagent using a clean stick. Spread the mixture overan area of 15mm Gently rock the slide to and fro and look for Record the if present indicates a positive resultAdvantages1.

9 Can be used in emergency and BLOOD camps for preliminary Easy to perform3. QuickDisadvantages1. Not reliable for weak reactions as negative results cannot be Serum testing cannot be The test mixture tends to dry Drying causes aggregation of cells which can be interpreted as Less sensitive than tube technique. 53 ABO BLOOD GroupingHEMATOLOGY AND BLOOD BANK TECHNIQUEMODULEH ematology and BloodBank TechniqueNotesABAgglutinatesof reducesNo agglutinationBlood group AABB lood group BABB lood group A-BABB lood group OFig. techniqueThis is the recommended method for GROUPING . It involveszcell GROUPING or forward GROUPING : testing test red cells with known or serum GROUPING : testing serum of donor/patient with known procedure for cell and serum GROUPING is described separately but in allsamples both the procedures should be done simultaneously and the required1.

10 Monoclonal Antisera-A and Antisera-B. Antisera-A, B is Normal saline3. Known cells of group A, B, OEquipment required1. Centrifuge2. Glass tubes 12 100 mm3. Glass tubes 75 10 mmHEMATOLOGY AND BLOOD BANK TECHNIQUEMODULEABO BLOOD GroupingHematology and BloodBank Technique 54 NotesCell or forward groupingIn this the donor/patient red cell are tested with known Check that the name and number of the donor/patient on the vial matcheswith the form. Write the same donor number on each tube in which groupingwill be Centrifuge the sample to separate the cells and Prepare a 2-5% cell suspension of test red cells in normal saline as followszAdd the cells to a pre labeled tube (75 10mm) filled three fourthwith normal and centrifuge at 1000- 2000 rpm for 1-2 minutes.