Blood Types
Blood types are classified according to the presence or absence of agglutinogens (antigens) present on the surface of red blood cells, or agglutinins, also called antibodies. Thus, blood are classified into 4 types according to the ABO system into:Blood Type A: One of the most prevalent kinds, containing anti-B (also known as anti-B) antibodies, may only accept blood from persons with Blood Type A or O;
Blood B: One of the rarest types, includes anti-A (also
known as anti-A) antibodies, and may only be transfused by persons of
blood types B or O;
AB blood : It is one of the rarest varieties
and lacks antibodies to A or B, allowing it to accept any type of blood
without experiencing any negative effects;
O blood Group:
Sometimes referred to as the universal donor and one of the most
prevalent kinds, has anti-A and anti-B antibodies and is only compatible
with type O donors; otherwise, agglutination may occur.
Genetic determination of ABO blood types
The
presence or absence of agglutinogens in people's blood is determined by
the IA, IB or i genes. The IA and IB genes are the most dominant over the i
gene. The IA gene, for example, determines the production of an enzyme
that synthesizes the A agglutinogen. Therefore, if a person has the IA
IA genotype and another person has the IA i genotype, the red blood
cells of both have the A agglutinogen, that is , they have blood type A.
Something similar occurs in the case of people with blood type
B. But people with type AB have genotype IA IB, as there is no dominance
between these two genes. These people are capable of synthesizing both A
and B agglutinogens. Finally, a type O person has genotype ii, that is,
they do not have the necessary enzymes to manufacture either of the two
agglutinogens.
The importance of blood types - transfusions
The
discovery by the Austrian physician Karl Landsteiner, in 1900, that
there was incompatibility between the blood of certain people, paved the
way for the identification of various blood types, including those of
the ABO system. Although it is not the only system of blood groups, it
is of the greatest practical importance at times of transfusion.
What can happen when a person with type A blood receives type B blood?
Since
there are anti-B agglutinins in the receiver's plasma, these substances
act as antibodies against the B agglutinogens existing in the donor's
red blood cells, causing the rupture of these red blood cells and a
reaction known as agglutination reaction. Note that the same reaction
will occur if a type A person receives blood from a type AB person.
Type
AB people do not have any of the agglutinins of the ABO system and this
means that they can receive, by transfusion, blood of any type. Such
people are called universal recipients and those with type O blood are
universal donors. This means that they can donate blood to anyone, since
their red blood cells do not have agglutinogens. Even if the receptor
has agglutinins, the agglutinins will have no substance to react
against.
The Rh Factor
The ABO system is not the only
one to be considered when talking about blood transfusion. There is
another important aspect that must be taken into account: the Rh factor,
or Rhesus factor. This blood trait was discovered in 1940 by two
researchers named Landsteiner and Wiener, who performed experimental
blood transfusions on rhesus monkeys.
Basically, the Rh positive
occurs when the individual presents a certain antigen on the surface of
his red blood cells. People who do not have this characteristic in
their blood cells are of the Rh negative type. Unlike the ABO system, in
the Rh system, agglutinins do not occur spontaneously. This means that
virtually all people are born without anti-Rh agglutinins.
For
someone to have anti-Rh antibodies, that individual must be exposed to
the Rh antigen. This can occur both by blood transfusion and in
conditions of pregnancy, in which the Rh factor is negative in the
mother and positive in the fetus. In such cases, anti-Rh agglutinins
develop and both the person who received the transfusion and the person
who is pregnant become sensitized.
The problem, in both
situations, is in the second contact with Rh positive blood. In the case
of another blood transfusion, under the same conditions, the
recipient's blood may undergo agglutination or his red blood cells may
rupture (hemolysis). In relation to pregnancy, if the woman is again
giving birth to an Rh positive baby, the mother's anti-Rh agglutinins
can cross the placenta, causing agglutination of the fetus' erythrocytes
— a disease known as fetal erythroblastosis.
Regarding blood
transfusions, people with Rh positive (Rh+) can receive donations of the
same Rh and also of Rh negative. Already Rh negative carriers, they can
only receive their type, otherwise there will be a risk of blood
agglutination and hemolysis.
Compatibility table for blood donation
The following table shows who you can donate blood to and who you can receive it from:
| Blood Types |
Can Donate To |
Can Receive From |
|||
| Blood Type A+ |
AB+ and AB- |
A+,A-,O+ and O- |
|||
| Blood Type A- |
A+,A-,AB+ and AB- |
A+ and O- |
|||
| Blood Type B+ |
B+ and AB+ |
B+,B-,O+ and O- |
|||
| Blood Type B- |
B+,B-,AB+ and AB- |
B- and O- |
|||
| Blood Type AB+ |
AB+ |
all |
|||
| Blood Type AB- |
AB+ and AB- |
A-,B-,AB- and O- |
|||
| Blood Type O+ |
A+,B+,AB+ and O+ |
O+ and O- |
|||
| Blood Type O- |
all |
O- |
What is your child's blood type?
Usually
the child's blood type is identified shortly after birth through the
heel prick test. However, the child's blood type can also be identified
through routine blood tests or at the request of the child's
pediatrician in order to determine the diagnosis of any disease.
In
pregnancy, when the mother is Rh negative and the baby is positive,
there is a probability that the pregnant woman will produce antibodies
to eliminate the baby, which may lead to an abortion. Therefore,
pregnant women with this blood type should consult the gynecologist to
check when there is an indication of anti-D immunoglobulin injection,
but there are never serious problems in a first pregnancy.
Who can donate blood
Blood donation takes an average of 30 minutes and some requirements must be respected, such as:
*Be
between 18 and 65 years old, however people aged 16 and over can donate
blood as long as they have authorization from parents or guardians and
meet the other requirements for donation;
*Weigh more than 50 kg;
*Wait a year after curing an STI.
How to donate blood
Rarest blood type
*If
you have a tattoo, wait between 6 and 12 months to make sure that you
have not been infected with any type of hepatitis and that you are still
healthy;
*Never have used illicit injectable drugs;*Wait a year after curing an STI.
Men
can only donate blood once every 3 months and a maximum of 4 times a
year and women every 4 months and a maximum of 3 times a year, since
women lose blood every month through menstruation, taking longer time to
replenish the amount of blood withdrawn.
Before donation,
it is important to avoid consuming fatty foods at least 4 hours before
donation, in addition to avoiding fasting. Therefore, it is recommended
to have a light meal before donating blood and after the donation, have a
snack afterwards, which is usually provided at the donation site. In
addition, it is indicated to drink plenty of fluids, not to smoke for at
least 2 hours after the donation and not to perform very intense
physical activities, as there may be a risk of fainting, for example.
The
person who wants to donate blood must go to one of the blood collection
stations, fill out a form with several questions about their health and
lifestyle. The form will be analyzed by an expert and, if the person is
able, they can then sit in a comfortable chair for the donation to be
made.
A nurse will place a needle in a vein in the arm, through
which the blood will flow into a bag designed to store the blood. The
donation lasts approximately half an hour and it is possible to ask for
leave from work that day, without having your salary deducted.
At
the end of the donation, the donor will be offered a reinforced snack
to replenish his energy, as it is normal for the donor to feel weak and
dizzy, despite the amount of blood withdrawn not reaching half a liter
and the body will soon recover this loss .
It is safe to
donate blood and the donor does not catch any disease, because he
follows national and international blood safety standards from the
Ministry of Health, the American Association and the European Council of
Blood Banks.
There is a
blood type so rare that less than 50 people in the world are known to
have it. Scientifically known as Rh null (Rhesus null), it is often
referred to as “golden blood” because of its extreme rarity — and its
value to others.
There are four main blood groups: A, B, AB, and
O. This grouping is determined by the presence of A and B antigens that
will trigger an immune response if the red blood cell is introduced
into someone who is not a match (as in the case of a blood transfusion).
Blood type A has A antigens, blood type B has B antigens, blood type AB
has both antigens, and blood type O has no antigens either.
In addition
to the A and B antigens, there are other proteins found in red blood
cells (blood cells) called the Rh factor, the presence or absence of
which determines whether a blood type is positive (+) or negative (-).
While there are actually 61 blood group antigens (Rh antigens), the
negative/positive divide refers to the absence or presence of one in
particular—the Rh(D) antigen.
A person can only donate blood to
someone with compatible blood antigens. Thus, people with Rh− blood can
donate blood to both Rh− and Rh+ recipients, as Rh− lacks the
problematic protein. However, those with Rh+ blood cannot donate to Rh−
recipients. Rh positive is much more common than Rh negative, although
there is some variation between different populations.
