Blood Typing

Procedure1. Materials were prepared. Glass slide was wiped with clean tissue paper.2. After washing hands with soap and water, fingertip was sterilized with alcohol and was pricked with a sterile

lancet.3. 3 drops of blood was placed separately on a glass slide. Punctured area was then pressed with cotton ball

soaked in alcohol.3. One drop of anti-A serum, anti-B serum and anti-D serum was added to each blood drop respectively.4. Serum and cells were mixed with an applicator stick. Agglutination was noted.

Genotype PhenotypeOO OAA, AO ABB, BO BAB AB

1. The ABO blood group Antigens are encoded by one genetic locus, the ABO locus. The ABO Locus has three alternative (allelic) forms—A, B, and O. A child receives one of the three alleles from each parent, giving rise to six possible genotypes and four possible blood types (phenotypes). Erythrocytes have surface projecting H antigens that Are subject to modification by an enzyme. The ABO locus, which is located on chromosome 9, contains seven exons that span more than 18 kb of genomic DNA. Exon 7 is the largest and contains most of the coding sequence. The ABO locus (chromosome 9), encodes a glycosyltransferase. The ABO locus has three main alleleic forms: A, B, and O. The A allele encodes a glycosyltransferase that bonds -α N-acetylgalactosamine to the D-galactose end of the H antigen, producing the A antigen. The B allele encodes a glycosyltransferase that bonds

-D-galactose to the D-galactose end of the H antigen, creating the B antigen. In the case of the O allele, whenα compared to the A allele, exon 6 lacks one nucleotide (guanine), which results in a loss of enzymatic activity. This difference, which occurs at position 261, causes a frameshift that results in the premature termination of the translation and, thus, degradation of the mRNA. This results in the H antigen remaining unchanged in the case of O groups. (Note: nice to know nalang yung mga exon chuva diyan)

2. An antigen/agglutinogen is a substance, usually a membrane (ie “surface”) protein that has the ability to provoke an immune response and the ability to react with the ANTIBODIES (or cells) that result from the immune response.

3. ANTIBODIES/immunoglobulins/agglutinin are protein molecules produced by certain cells, as part of the immune response, against a specific antigen. The ANTIBODIES combine with (they “latch onto”) that specific antigen to neutralize, inhibit, or otherwise destroy it. The combination of an ANTIBODY with the antigen for which it is specific is called an antigen/ANTIBODY complex and the process of antigen/ANTIBODY-complex-formation is called agglutination. Each IgG molecule consists of two heavy chains and two light chains. The two heavy chains are linked to each other by disulfide bonds and each heavy chain is linked to a light chain by a disulfide bond. In any given immunoglobulin molecule, the two heavy chains and the two light chains are identical, giving an antibody molecule two identical antigen-binding sites and thus the ability to bind simultaneously to two identical structures.

Anti-A & Anti-B are not naturally occurring antibodies. They are not present at birth and only appear 2-8/12 months. These antigens are Triggered by A & B antigens in food and bacteria

4. Once antigen/ANTIBODY complexes form, they now “stick out” quite a long ways from the cell’s surface and make the cells hang-up on each other as they pass by. This causes bunches of these similar cells to “clump-up”, or agglutinate. Agglutination renders cells useless and easier for macrophages to come along, engulf large quantities of them, and destroy/digest them.

5. Organisms possess antibodies to antigens they DO NOT possess. Example: If you have antigens A, C and E – but NOT antigens B, D or F….then you would have Anti- bodies b, d, and f. You would NOT, of course, have antibodies a, c nor e….because you would NOT want to agglutinate your own cells!! Organisms may be born with many of these antibodies; they may acquire some from nursing, or they may manufacture many more upon exposure to various antigenic agents. (It is the activated B-lymphocytes, maturing into plasma cells, that manufacture these antibodies or Igs).

6. Landsteiner’s Law• Only applicable to the ABO system• 2 laws :

(I) 1st Law: When an Agglutinogen is present on the membrane of RBC, the corresponding agglutinin must be absent in the plasma of the person.

Eg: RBC contains A –Ag; plasma must not contain α agglutinin; otherwise there will be death! (i) 2nd Law: When the RBCs in an individual is devoid of agglutinogen, plasma shall contain the

corresponding agglutinin. Eg: RBCs contain no B or A antigen. In the plasma of this individual; there must be anti-A and anti-B agglutinins. Therefore: “A” group blood must contain β-agglutinin in the plasma and Group O blood must contain both α and β agglutinins in the plasma.

7. Before blood cells can be transfused, they must be typed and cross-matched so that transfusion reactions are avoided. People have different blood types and transfusion of incompatible blood can be fatal. RBC cell membranes, just as do ALL body cells, bear highly specific glycoproteins (antigens) on their external surfaces, which identify each of us as unique from all others. One person’s RBC proteins may be recognized as foreign if transfused into someone with a different RBC type, and the transfused cells may be agglutinated and destroyed. At least 30 varieties of naturally occurring RBC antigens are common in humans. Besides these, perhaps 100 others occur in individual families (“private antigens”) rather than in the general population. The presence or absence of each antigen allows each person’s blood cells to be classified into several different blood groups. Antigens determining the ABO and Rh blood groups cause vigorous transfusion reactions (destroying foreign erythrocytes) when they are improperly transfused. Thus, blood typing for these antigens is always done before blood is transfused. Additional antigens (such as the M, N, Duffy, Kell, and Lewis factors) are mainly of legal or academic importance. Because these factors cause weak or no transfusion reactions, blood is not specifically typed for them unless the person is expected to need several transfusions, in which case the many weak transfusion reactions could have cumulative effects. The most important blood groups for RBC’s must be typed are the ABO and Rh groups which will be described now.

8. the ABO blood groups are named based on the presence or absence of two antigens: type A and type B. A person has blood type A if there are A antigens present on the RBCs membranes; blood type B if there are B antigens present on the RBCs membranes, blood type AB if there are BOTH A antigens and B antigens on the RBCs membrane, and type O if there are NEITHER A antigens nor B antigens on the RBCs membranes. (Note: this is read “O”, as in the letter “O”; but there is NO SUCH THING AS “O” antigens. Hence, this really stands for “zero”, “zilch”, “nada”, “none” NO ANTIGENS!!)

9. The other “half” of the blood typing story involves the ANTIBODIES present in the plasma. Again, as shown in a person has the ANTIBODIES opposite of the antigens he/she possesses. That is, someone with type A blood has anti-B antibodies; while someone with type B blood has anti-A antibodies; persons with type AB would have neither antibody, those with type O blood would have BOTH anti-A and anti-B antibodies.

10. When mismatched blood is infused, a transfusion reaction occurs in which the donor’s RBCs are attacked bythe recipient’s plasma antibodies. (Note: the donor’s plasma antibodies may also be agglutinating the host’s RBCs, but they are so diluted in the recipient’s circulation that this does not usually present a serious problem.) The initial event, agglutination of the foreign RBCs, clogs small blood vessels throughout the body. During the next few hours, the clumped RBC’s begin to rupture or are destroyed by phagocytes, and their hemoglobin is released into the bloodstream…when the rxn is exceptionally severe, the RBCs are lysed almost immediately. These events lead to two easily recognized problems: (1) the O2 carrying capability of the transfused blood cells is disrupted, and (2) the clumping of RBCs in small vessels hinders blood flow to tissues beyond those points.

Less apparent, but more devastating, is the consequence of hemoglobin escaping into the bloodstream. Circulating hemoglobin passes freely into the kidney tubules where it may precipitate, blocking the kidney tubules and causing renal shutdown. If shutdown is complete (aka acute renal failure), the person may die! (Transfusion rxns can also cause fever, chills, low blood pressure, rapid heartbeat, nausea, vomiting, and general toxicity; but in the absence of renal shutdown, these rxns are rarely lethal. Tx of transfusion rxns is directed toward preventing kidney damage by infusing alkaline fluids to dilute and dissolve the hgb and flush it out of the body. Diruretics, which ↑ urine output, are also given.)