英国纽卡斯尔大学 生理学课件

1、Physiology PSC1001 Lecture 3,Blood,Dr Chris Baldwin christopher.baldwinncl.ac.uk,Blood groups,By the end of this session you should be familiar with,1. The physiological principles of blood groups,2. The ABO System,3. The Rh Group,4. Appreciate the clinical relevance of ABO and Rh,Blood Groups,5. Ot

2、her Blood Groups,Blood Groups,A complex mixture of glycoproteins and glycolipids are found on the surface of red blood cells.,Thus if an individual is exposed to molecules that are not on self RBC they will have the capacity to mount an immune response to the foreign, glycolipids and proteins.,The e

3、xpression pattern of these molecules varies between individuals.,A molecule that can induce an immune response is termed an antigen and thus these molecules are termed red blood cell surface antigens.,There are 30 human blood group systems and over 600 different blood group antigens have been descri

4、bed.,An complete blood group is described as the set of 29 RBC surface antigens of the surface of an individuals RBC.,Usually only the ABO blood group system and the presence or absence of Rhesus D antigen (Rhesus factor) are determined to describe blood type.,Blood Groups,Blood groups are inherited

5、 and represent contributions from both parents.,The ABO System,The ABO system is controlled by the genes A, B, H and h.,H is dominant and codes for a fucosyl transferase enzyme that converts a precursor substance in RBCs to H Substance (H substance is a glycoprotein).,Therefore HH individuals make H

6、 substance Hh individuals make H substance hh individuals do NOT make H substance,hh (Oh) individuals,These individuals are described as having the Bombay phenotype. Note:,They are very rare in the population (1/250 0000) except in parts of India (1/8000).,These individuals may posses the A or B gen

7、e but as no precursor substance H is made they will not have any ABO antigens. There is no ill effect but people with this blood group must only have transfusions from other individuals with this blood group,The A and B alleles,These code for the transferase enzymes: A-transferase (N-acetyl galactos

8、amine transferase) or B-transferase (galactose transferase),These enzymes transfer sugar molecules to H substance:,H substance,A Transferase,A substance,H substance,B Transferase,B substance,A transferase only makes A substance B transferase only makes B substance,The A and B alleles,A and B substan

9、ce differ only in the sugar molecule that is added to the galactose on the glycoprotein H-substance with A transferase adding N-acetyl galactosamine and B transferase adding galactose.,The A and B alleles,Some individuals posses both A and B transferases and thus add either galactose or N-acetyl gal

10、actosamine to the galactose on the glycoprotein H substance.,For the AB alleles individuals may be genotype AA make A substance only AO make A substance only BB make B substance only BO- make B substance only AB- make A and B substance OO- make H substance only,The A and B alleles,Blood Group Genoty

11、pe RBC substance made AAAA substance AO B BB B substance BO ABAB A and B substance OOO H substance,The A and B alleles,A and B Blood Groups,AB Blood Groups,A, B and H substances are glycoproteins and an individual can raise an immune response against these molecules i.e they are antigens. Individual

12、s that do not have A or B substances on their RBCs will develop antibodies against either or both without ever having been exposed to blood that carries these antigens. A and B substances are widespread in nature (including gut bacteria) and so individuals raise antibodies against them soon after be

13、ing born.,Blood Group Genotype Antigens Antibodies in blood in blood AAAA substance AO B BB B substance BO ABAB A and B substance none OOO H substance and ,ABO Blood Groups,Note that blood group antigens are also known as agglutinogens and the antibodies raised against them are known as agglutinins.

14、,When the plasma of blood group A individual is mixed with the RBCs of a blood group B person, the b antibodies in the plasma cause clumping (agglutination) of the RBCs.,ABO Blood Groups,Clinical relevance of ABO groups,The donated blood will obviously also contain antibodies that could potentially

15、agglutinate the recipients RBCs. However clinically this is of less significance because the donated blood (and hence antibodies) are quickly diluted by the recipients blood.,The RBCs of blood donated to an individual will all agglutinate and eventually lyse if the recipient contains antibodies agai

16、nst them (this is known as a haemolytic transfusion reaction).,Clinical Relevance of ABO groups,However: Persons with Blood Group AB are universal recipients. They can receive blood of any ABO group without developing a haemolytic transfusion reaction. Persons with Blood Group O are universal donors

17、. Their blood can be given to any other without developing a haemolytic transfusion reaction.,Because mismatching of blood groups will result in a haemolytic transfusion reaction, donated blood is always correctly matched before any transfusion.,The Rhesus Group,There are a number of rhesus antigens

18、 which may be present on RBC but the most common and most important is the D antigen (agglutinogen).,Apart from the ABO system, those of the Rhesus (Rh) system are of the greatest clinical relevance.,They are named after the rhesus monkey in which they were discovered,85% of Caucasians (99% Asians)

19、have the D antigen on their RBCs (Rh+ve). 15% of Causasians people lack the D-antigen on their RBCs (Rh ve).,Anti-RhD antibodies are not normally produced by sensitisation to environmental antigens.,Rhesus Antigens,During birth there is often leakage of the babies RBC into the mothers circulation. If the baby is Rh +ve and the mother is Rh-ve the red cells will cause the mother to develop antibodies to the D antigen.,These antibodies are normally of the IgG class.,Th