Erythrocytes contain a number of antigen types( at least 600) belonging to a membrane grouped in several systems.Since the antibodies formed against antigens (abo antibodies) cause the agglutination of erythrocytes, they are called agglutinogens.The erythrocyte membrane contains A, B and plasma antigens known as agglutinins: alpha( against A) and beta( against B).The corresponding / homologous agglutinogen and agglutinin usually do not coexist in one person’s blood( Landsteiner’s rule).There are four blood groups depending on their presence in the OAB system.The blood type name is specified by the agglutinogen
|Blood group||Genotype||Agglutinogen||Agglutinins||Frequency in population|
|O I||OO||—-||alpha, beta||47 %|
|A II||OA or AA||A||beta||41 %|
|B III||OB or BB||B||alpha||9 %|
|AB IV||AB||A,B||—-||3 %|
Agglutinogens are glycolipids on the surface of the erythrocyte.They appear in the third month of fetal life and are found in all tissues except the lens, vitreous; less in nerve tissue, cornea, cartilage, compact bone, but some secretions are found: saliva, gastric and intestinal juice, milk, semen, amniotic fluid.Agglutinins occur in intrauterine life for 3- 6 months and reach their highest level in 10 years.Some erythrocyte samples from the A, B or AB group show weak reactions with specific antiserum, which characterize the presence of antigens that are variations or subgroups of the ABO system.Subgroups A: A1( A loud) and A2( A weak) which are characterized by low anti- A serum agglutination reactions.These subgroups divide the groups A and AB in A1, A2, A1B and A2B.Other subgroups A and B are extremely rare and unimportant for the newborn’s hemolytic disease.Hereditary groups of blood are transmitted; each person has two genes( one from each parent).They are useful in this sense in establishing paternity.
When several blood types( agglutinins come into contact with homologous agglutinogens) are incompatible, red blood cells are agglutinated by their surface attachment agglutinins, so that cells are gathered into a conglomerate during agglutination.These conglomerates cause small blood vessels to overshadow the circulatory system.In the next hours / days, these will be phagocytized and erythrocyte membranes that cause hemolysis( plasma hemoglobin release) will be eliminated.
Principle of ABO blood group test
- The determination is based on agglutination, antigen- antibody reaction between erythrocyte antigens A, B and serum agglutinins alpha, tube beta or slide beta.
- You can use the Beth- Vincent test, which identifies agglutinogens when we know agglutinins or the Simonin test, which identifies agglutinins when we know agglutinogens.
Material required for ABO Blood Grouping
- Glass slides (possibly with well)
- erythrocytes test O, A, B; collection blood from fingertip required needle
- wool and alcohol for Beth Vincent method
- blood collected by venipuncture for serum separation for Simonin method.
- Anti –A, anti-B, anti-AB; anti- A contains agglutinins alpha, anti-B agglutinins beta and anti-A B agglutinins alpha and beta.
- Erythrocytes test are group O, A and B.
Beth-Vincent Blood grouping method procedure
- Successively put on a slide with different pipettes cleaned with alcohol, one drop of anti-AB, Anti-B and Anti-A.
- Disinfect the pulp of the finger with alcohol and prick with a sterile needle.
- With upper blades put a small amount of blood in each drop of the antisera (Anti-A,Anti-B and Anti-AB) mixing it with different applicator stick.
- The drop of blood should be 10/20 times lower than the Anti-sera.
- Now,Slowly move the slide circularly and watch for the agglutination appearance in the first 2-3 minutes.
Result and interpretation
These situations may be:
- Agglutination is not present or observed in all three circle, the blood being investigated belongs to group O
- Agglutination only occurs with antisera- AB and anti- A, we have a blood group A
- Agglutination only takes place with antisera- AB and anti- B, We have a blood group B
- Agglutination occurs in all three circle,we have a Blood group AB.
Simonin blood group test method procedure
- On a glass slide, add three drops of serum on each ring
- Then add Blood group O washed cells on Circle the first ring,Blood A washed cells on the second ring and Blood group AB on the third ring
- Gently mix the reagents using a different applicator stick respectively
- Erythrocytes or washed cells and serum ratio should be about 1 to 10.
- Reading is done by the slow rotation of the slide in the first 2 to 3 minutes
Result and interpretation
- Agglutination occurs with erythrocytes group A and B,This corresponds to group O (serum containing both agglutinins type)
- Agglutination occurs with erythrocytes B and without agglutination with erythrocytes A (serum contains agglutinins beta),this corresponds to group A
- Agglutination occurs in erythrocytes group A and but no agglutination with erythrocyte group B,this corresponds to the group B, serum researched containing agglutinins alpha;
- No agglutination occurs in any of the drops,Therefore, agglutinins are missing hence this correspond to serum group AB.
Possible sources of Error
- Use of infected/ old and expired antisera may cause non specific reactions or lack of the agglutination
- Delay of reading may result to false agglutination
- Use of outdated test erythrocytes
- Abnormal proportion between blood and antisera, serum and erythrocytes test.
Determination of Rh SYSTEM
The Rh is another group of antigens of the erythrocyte membrane.There are six antigens in the Rh system( C, D, E, c, d, e).The most important antigen is antigen D( or Rh antigen from the Macacus Rhesus monkey), which is found on 85% of the population of the RBC membrane.Caucasians with this antigen are referred to as Rh positive( 85 percent) and those who do not have Rh negative.The presence of c antigens excludes C and other antigens.
The following major differences exist between the ABO and the Rh system: -Rh- antigen is only present in erythrocyte membranes( not in other cells); -Rh antibodies are not spontaneously present in plasma in the Rh system.In the following circumstances, these antibodies appear:
- After transfusion of Rh negative blood to Rh positive( high concentrations after 2- 4 months)
- Rh negative mother and Rh positive fetus( Rh positive dominant).
An Rh negative mother with Rh positive fetus develops in the first pregnancy usually not a lot of anti Rh agglutinins to produce adverse effects; 3 percent of rh- positive children born to the second pregnancy erythroblastosis signs of fetal( or hemolytic disease of the newborn) and 10 percent of children in the third pregnancy develops the disease.
Principle of Rh System
It is based on the agglutination reaction between serum anti Rh (D) and blood research.
- Anti Rh serum
- glass pipettes
- needle wool
Rh system procedure
- Put on a glass slide a drop of anti Rh serum
- Add a drop of blood (from fingertip) to the slide.
- Mix gently and rotate the slide in a circular motion.
- Read the first 2-3 minutes
Result and Interpretation(blood type explanation)
- Agglutination is observed,this is a rhesus blood type positive OR Rh +
- If no agglutination occurs it is Rh negative.
Hemolytic Disease of the Newborn or newborn diseases
Hemolytic disease of the newborn, also known as hemolytic disease of the fetus and newborn or erythroblastosis fetalis, is an alloimmune condition (blood disorders in newborn babies) that develops in a fetus, when the IgG molecules( one of the five main types of antibodies) produced by the mother pass through the placenta.Some of these antibodies attack red blood cells in the fetal circulation; the red cells are disintegrated and the fetus can develop anemia and reticulocytosis.This fetal disease ranges from mild to very severe and fetal death due to cardiac insufficiency( hydrops fetal).When the disease is moderate or severe, many erythroblasts in the fetal blood are present and these disease forms can be called erythroblastosis fetalis( or erythroblastosis fetalis).
How to Manage HDN
- Replace transfusion with a blood group compatible with both the infant and the mother( complete replacement of newborn blood with Rh- negative blood);
- Intravenous anti- D serum( anti- D IG) administration to the Rh- negative mother during the first 36- 72 hours after birth( destroy Rh positive erythrocytes reached maternal circulation).