Topic 8: Human and animal blood groups Flashcards
What should be mentioned in this topic?
- Basics about blood groups
- Hemagglutinogens
- Formation of Hemagglutinins
- Agglutination
- Human Blood Groups
- AB0 Blood Type Reactions
- Rh Blood Group
- Rh-incompability
- Animal Blood Groups
- Blood Transfusion
Basics about blood groups
- Blood groups are complex antigens appearing in the surface of the blood cells.
- 15 types of human blood groups (two of these are AB0 and Rh).
- Important during blood transfusions.
- Antibodies are produces postnatally against those human red blood cell antigens that the person does not possess.
- They circulate in the plasma.
- These antibodies agglutinate other individuals’ red blood cells.
Hemagglutinogens
-They are compounds on the surface of the RBC forming antigens.
-Substances initiating the production of the blood-agglutinating-antibody.
-Their appearance is determined by genes located on different chromosomes.
One blood group gene is responsible for the expression of one blood group.
-Antigens found on the surface of the RBCs are glycoproteins and glycolipids.
Natural Hemagglutinins
- Antibodies are present without previous immunisation.
- Agglutinate the red blood cells of animals expressing the corresponding antigens.
Hemagglutinins:
Artificial Hemagglutinins
- Antibodies form only after previous immunisation
- Immunisation can be:
- Natural–Rh
- Artificial
Hemagglutinins:
Hetero/Isohemagglutinins
- Hetero-: Agglutinates RBCs of the other species
- Iso-: Agglutinates RBCs of the same species
Formation of Hemagglutinins
- Early immunisation postnatally
- Antibodies are not present in newborn
- Antibody titer is constantly growing
- Antibodies may disappear in elderly individua ls
Agglutination
The reaction between the RBC and the plasma antibodies occurs in two basic forms:
- Agglutination (human)
- Hemolysis (animals)
- These two reactions occur together or alone.
Human Blood Groups
- The H antigen encoded by the H gene forms the basic structure of the most important blood type system (AB0).
- No H = bombay-group
- There are further groups synthesized on top of this universal antigen, that is why A, B and AB groups are formed.
- If there are no additional groups the 0 group is formed.
AB0 Blood Type Reactions
- Type of a red blood cell belonging to an unknown blood group can be determined by agglutination reaction.
- We have the blood cells bearing unknown A, B or AB antigens react with a serum containing specific antibodies directed against the antigens.
- In case of incompatibility agglutination is seen, that can be used for determination of the blood cells’ antigen-type.
Rh Blood Group - Pregnancy
- Rh negative mother can be immunised by the blood cells of her own Rh positive foetus.
- The forming antibody is not IgM- type like in the AB0 case, but IgG-type that crosses much easier the placenta.
- In case of the first foetus no damage occurs because the foetal RBC usually gets into the mother’s body only via micro-injuries during the delivery.
- During the second pregnancy the small amount of RBC entering the mother’s sensitized immune system stimulates the production of anti-Rh antibodies (IgG). These get back to the foetus.
- They dissolve the foetal red blood cells and a clinical pattern called erythroblastosis feotalis occurs causing yellow jaundice and in its last stage, the death of the foetus.
Rh-Incompatibility
The other important case of Rh-incompatibility is when an Rh negative recipient gets RBC from a Rh positive donor. The Rh-negative recipient is immunised and the forming IgG antibody dissolves the red blood cells of the recipient.
Animal Blood Groups
The animal blood group systems significantly differ from those of the human ones.
- In most cases there are no naturally formed antibodies against the RBC-antigens of other individua ls.
- In many cases the blood type antigens appear in the plasma, too.
- Most of the time the artificially formed antibody has a haemolysing and not an agglutinating character.
Blood Transfusion
Substitution of lost RBCs and assuring normal gas transport.
In large animals a small amount is first transfused. If there is no sign of incompatibility the whole amount is transfused.
In small animals the three drop test must be always completed; 1 drop of donor blood cells, 1 drop of recipient’s plasma and 1 drop of physiological sodium chloride solution. If there is no hemolysis or agglutination, the transfusion can be completed without the complete knowledge about the blood groups.
For cat as a life saving act blood of a donor dog can be transfused.
Why is the blood transfusion less trouble in the animals?
- Blood transfusion means less trouble in animals than in humans for two reasons:
- There are few naturally produced antibodies against RBC antigens. The antigens against which antibodies can be found in other individuals can be found not only on the red blood cells, but in the plasma too. Therefore in case of transfusion the antibody is neutralised in the plasma already and its RBC dissolving capacity diminishes.
