blood groups

lab8
blood group system
before the discovery of the blood groups system, the attempts to transfuse blood were unsuccessful, because they resulted in clumping of blood cells, rupture and clotting in the blood vessels called transfusion reactions leading to death. until 1935 the scientist karl land steiner demonstrated that transfusion reactions are caused by interactions between antigens (also called agglutinogens) and antibodies (also called agglutinins).
the membranes of the r.b.cs have glycoprotein molecules called antigens (ags) specific for the individuals, and in the plasma there are proteins called antibodies (abs). so in human the ags on the surface of the r.b.cs found in over than 633 types organized into 22 system one of them called blood group system includes only two types abo & rh blood group system.
1- abo blood group system
abo blood group system is based on the presence or absence of the a & b ags on the r.b.cs. (see the table 1).
blood group ags on r.b.cs abs in serum genotypes
a a anti-b aa or ai
b b anti-a bb or bi
ab a&b _ ab
o _ anti-a, anti-b oo
table-1 - show the abo system in human
we can understand that in the same group there is abs in serum differing from ags which is carried on r.b.cs., in order to prevent the spontaneous agglutination and hemolyse the r.b.cs or cause clots in the blood vessels.
in some rare cases there are incompatibility between a pregnant mother and her baby in the type of abo blood group, but this is not problem for the child, because first: the fetus has few abo ags and not well developed to activate the immune system of the mother than adult. second: most of the
abs of the mother is belong to the type igm is very large to cross the placenta to the baby r.b.cs.
2- rh blood group system
another important blood group is the rh factor. it s discovered in 1943
by land steiner in rhesus monkeys rh factor is a protein on r.b.cs membranes called antigen-d, this ag is found in 858 of people (rh+) and 15 % does not inherit this ag (rh-).
the incompatibility of rh is very common and cause of the hdn disease in the new born. this happen when rh- female marries rh+ male, there is 53 % chance of producing rh+ fetus (if the father has genotype rh+rh-) and 133 % chance of producing rh+ fetus ( if the father has genotype rh+rh+).
during pregnancy the mother and fetal circulations are separate, but at the time of birth, hard contractions in the uterus cause destroy the blood vessels causing mixing of fetal and mother blood for hours, so number of fetus r.b.cs that carry the ag-d will enter the mother circulation and stimulate her immune system to produce abs called ab-d will cross the placenta to the fetal blood causing clotting and hemolyse of fetus r.b.cs which will destroyed within 1-2 week.
this case is deadly to the fetus, especially if the level of the abs was high and the dangerous increase in the continuous pregnancy, but if the level is low, the fetus my live with sever anemia, therefore this disorder is called hemolytic disease of new born (hdn). also the term erythroblastosis fetalis is also used to describe the hdn, because the blood smear from these babies show the presence of many immature r.b.cs (erythroblasts) because the r.b.cs were destroyed before mature.
in mild cases the treatment is the transfusion of blood or in some times used the exchange transfusion without abs. but the best treatment is the preventive treatment by give to the rh- mother immediately after birth her first child (rh+) a rhogam within 72 h. after birth. t
rhogam is rh-positive gamma-globulin (rh+abs) this ab will attach and destroy the fetus r.b.cs that enters the mother blood before her immune system is activated, so she can become pregnant with another rh+ child without any dangerous.
blood group test:-
principle:-
the principle is based on the antigen- antibody reaction and show agglutination.
reagents & equipments:-
1-blood group plate or microscope slides.
2-anti-a, anti-b, anti-d solution
3-stirrer.
specimen: - ,
the specimen is capillary or edta- anticoagulated blood.
procedure:-
agglutinalion tests are usually carried out in tubes or on slides for abo & rh grouping. here we will perform slide test.
1- put 3 dropings of the blood on a clean-dry glass slide (these dropings represent the ag).
2-* add droping of anti-a (represent the abs) to the first droping.
* add droping of anti-b (represent the abs) to the second droping.
* add droping of anti-d (represent the abs) to the third droping.
3-move the slide in circular motion.
4-slide must read within 5 min. to avoid the evaporation.
5-* if agglutination occurs in the first droping, it mean that the blood group is a.
* if agglutination occurs in the second droping, it means that the blood group is b.
* if agglutination occurs in the both dropings, it means that the blood group is ab.
* if there is no agglutination in both dropings, it means that the blood group is o.
* if agglutination occur in the third droping, it means that the blood rh+. if no it is rh- (see table 2).