Each one of us has a blood group or blood type and the classification is based on certain substances on the surface of red blood cells in the blood and these substances called antigens could be proteins, carbohydrates, glycolipids or glycoproteins. Blood groups and blood types are inherited and represent contributions from both parents. The formation of these groups would stem from the production of closely linked genes called alleles. There are about 30 human blood systems recognized by the International Society of Blood Transfusion including the ABO and rhesus systems that we commonly use. The 30 human blood group systems have resulted from over 600 antigens identified many of which are rare and found only in some ethnic groups. Some of the other blood groups include the Duffy, Kell, Lewis, McLeod Certain blood types may affect susceptibility to infections, an example being the resistance to specific malaria species seen in individuals lacking the Duffy antigen. The Duffy antigen, presumably as a result of natural selection, is less common in ethnic groups from areas with a high incidence of malaria. Blood groups tend to remain the same throughout life except in the rare instances of antigen suppression in infection, cancers, and autoimmune disease. Another common cause of blood type change can occur in bone marrow transplant where the recipient’s blood type is changed to the donor’s.
ABO blood group system
The ABO system as was mentioned earlier is the most important blood group system in human blood transfusion. The associated anti-A and anti-B antibodies are usually immunoglobulin M (IgM) antibodies. ABO IgM antibodies are produced in the first years of life by sensitization to environmental substances such as food, bacteria, and viruses. Everyone therefore belongs to one of four blood groups which would either be A, B, AB or O. Since the groupings are contributions from both parents the genotype which is the more detailed blood grouping usually end up in the four types. Blood group A therefore would have the genotype AA or AO, B would have BB or BO, AB would have AB and O would have OO.
Rh Blood group system
The Rhesus or Rh system is the second most significant blood-group system in human blood transfusion with 50 antigens. The most significant Rh antigen is the D antigen, because it is the most likely to provoke an immune system response of the five main Rh antigens. It is common for D-negative individuals not to have any antibodies, because anti-D antibodies are not usually produced by sensitization against environmental substances. However, D- negative individuals can produce antibodies following sensitizing events: possibly a foeto-maternal transfusion of blood from the foetus in pregnancy or occasionally a blood transfusion with D positive red blood cells. Rh disease can develop in these cases. When blood groups are designated, Rh negative is written with – sign and Rh positive written with + sign.
Transfusion medicine is concerned with the study of blood groups along with the work of a blood bank to provide transfusion service for blood and other blood products and these products must be prescribed by licensed medical practitioners in the same way as medicines. Much of the routine work done in blood banks involves the testing of the blood from donors and recipients to ensure that every recipient is given blood that is compatible with the donor. In the event of transfusion of incompatible blood, severe reactions can take place leading to the breakdown of red blood cells, kidney failure, shock, and even death. Patients should ideally be given their own blood or type-specific products to minimize the chance of a transfusion reaction. Risks can be further reduced by cross-matching blood, but this may be skipped when blood is needed in an emergency. Cross-matching involves mixing a part of the recipient’s serum with that of the donor’s red blood cells and to check whether clumps would form, a phenomenon called agglutination. If agglutination results, that particular donor’s blood cannot be given to the recipient. Rare blood groups usually cause supply problems for hospitals when they are needed for transfusion.
Haemolytic disease of the newborn
As has been earlier alluded to, a woman can make blood group antibodies if her foetus has a blood group that she does not have. This can happen if some of the foetus’ blood cells pass into the mother’s circulation at the time of childbirth or during an obstetric procedure such as an abortion or sometimes after a blood transfusion. This can cause rhesus disease or other forms of haemolytic disease of the newborn in the current pregnancy or subsequent pregnancies. This complication can however be avoided by giving the mothers an injection known as Rho(D) immunoglobulin within a specific period following delivery.
Universal donors and recipients
With regard to blood transfusion of whole blood and red blood cells, people with blood group O- are known as universal donors and those with blood group AB+ are called universal recipients. Despite these descriptions very rare reactions may occur from the lesser known blood groups. When transfusing plasma which is another blood product, O plasma becomes the universal recipients and AB becomes the universal donors.
Blood group compatibility
Blood group AB individuals have both A and B antigens on the surface of their red blood cells and their blood plasma does not contain any antibodies against either A or B antigen. Therefore, an individual with type AB blood can receive blood from any group (with AB preferable) but can donate blood only to another type AB individual blood group A individuals have the A and blood serum containing antibodies against antigen on the surface of their red blood cells, he B antigen Therefore, a group A individual can receive blood only from individuals of groups A or O (with A being preferable) and can donate blood to individuals with type A or AB.
Blood group B individuals have the B antigen on the surface of their red blood cells, and blood serum containing antibodies against the A antigen. Therefore, a group B individual can receive blood only from individuals of groups B or O (with B being preferable) and can donate blood to individuals with type B or AB.
Blood group O individuals do not have either A or B antigens on the surface of their red blood cells, but their blood serum contains anti-A and anti-B antibodies against the A and B blood group antigens. Therefore, a group O individual can receive blood from a group O individual, but can donate blood to individuals of any of the other ABO groups. O negative blood can be used in cases of dire emergencies where time is critical.
Blood grouping and paternity
In the past blood grouping was used to prove impossibility of paternity rather than to prove paternity. This means that blood grouping can be used to show that an AB father could not have fathered an 0 baby but this system cannot be used to show who the father is. DNA testing has come to replace this system with more accurate results.
Blood group and fertility
There is a myth that people with different blood groups or certain blood groups cannot have children when married. There is no restriction with regard to blood groups of spouses and fertility. A study done in Nigeria investigating blood group compatibility and fertility amongst couples found no evidence that different blood groupings could affect fertility in a couple. It is however worthy to note that a recent study done in US recently showed women with blood group O had lower fertility.
Blood group and diet
There is a lot of talk these days about particular diets that must be taken by particular blood groups for adequate health and this new belief is getting very popular. Current scientific evidence however does not support unique diets for particular blood types or groups.
It is very important for everyone to know his or blood group since this may be very important when one may need blood transfusion or be called on to be a donor. Moreover the knowledge of the rhesus status in women of childbearing age would be very pertinent in preventing miscarriages, haemolytic disease of the newborn and other complications.
Written Dr. Andre Kwasi Kumah, Supreme Physician