The Bombay Phenomenon: A History of Discovery. Universal Blood Donor

August 15th, 2017

Who does not know that people have four main blood types. The first, second and third are quite common, the fourth is not so widespread. This classification is based on the content in the blood of the so-called agglutinogens - antigens responsible for the formation of antibodies.

The blood type is most often determined by heredity, for example, if the parents have the second and third groups, the child can have any of the four, in the case when the father and mother have the first group, their children will also have the first, and if, say, the parents have the fourth and the first, the child will have either a second or a third.

However, in some cases, children are born with a blood type that, according to the rules of inheritance, they cannot have - this phenomenon is called the Bombay phenomenon, or Bombay blood.

Within the ABO/Rhesus blood group systems that are used to classify most blood types, there are several rare blood types. The rarest is AB-, this type of blood is observed in less than one percent of the world's population. Types B- and O- are also very rare, each accounting for less than 5% of the world's population. However, in addition to these two main ones, there are more than 30 generally accepted blood typing systems, including many rare types, some of which are observed in a very small group of people.

Blood type is determined by the presence of certain antigens in the blood. The A and B antigens are very common, making it easier to classify people based on which antigen they have, whereas people with blood type O have neither. A positive or negative sign after the group means the presence or absence of the Rh factor. At the same time, in addition to antigens A and B, other antigens are also possible, and these antigens can react with the blood of certain donors. For example, someone may have an A+ blood type and not have another antigen in their blood, indicating that they are likely to have an adverse reaction with an A+ blood donation that contains that antigen.

There are no A and B antigens in Bombay blood, so it is often confused with the first group, but there is no H antigen in it either, which can be a problem, for example, when determining paternity - because the child does not have any of the antigens in the blood that him from his parents.

A rare blood group does not give its owner any problems, except for one thing - if he suddenly needs a blood transfusion, then you can only use the same Bombay blood type, and this blood can be transfused to a person with any group without any consequences.

The first information about this phenomenon appeared in 1952, when the Indian doctor Vhend, conducting blood tests in the family of patients, received an unexpected result: the father had 1 blood type, the mother had II, and the son had III. He described this case in the largest medical journal, The Lancet. Subsequently, some doctors encountered similar cases, but could not explain them. And only at the end of the 20th century, the answer was found: it turned out that in such cases, the body of one of the parents mimics (fakes) one blood group, while in fact it has another, two genes are involved in the formation of the blood group: one determines the group blood, the second encodes the production of an enzyme that allows this group to be realized. For most people, this scheme works, but in rare cases, the second gene is missing, and therefore there is no enzyme. Then the following picture is observed: a person has, for example. III blood group, but it cannot be realized, and the analysis reveals II. Such a parent passes on his genes to a child - hence the “inexplicable” blood type appears in the child. There are few carriers of such mimicry - less than 1% of the world's population.

The Bombay phenomenon was discovered in India, where, according to statistics, 0.01% of the population have "special" blood, in Europe Bombay blood is even rarer - about 0.0001% of the inhabitants.

And now a little more detail:

There are three types of genes responsible for the blood group - A, B, and 0 (three alleles).

Every person has two blood type genes - one from the mother (A, B, or 0) and one from the father (A, B, or 0).

6 combinations are possible:

How it works (in terms of cell biochemistry)

On the surface of our red blood cells there are carbohydrates - “H antigens”, they are also “0 antigens”. (On the surface of red blood cells there are glycoproteins that have antigenic properties. They are called agglutinogens.)

Gene A encodes an enzyme that converts part of the H antigens into A antigens. (Gene A encodes a specific glycosyltransferase that attaches the N-acetyl-D-galactosamine residue to agglutinogen, resulting in agglutinogen A).

Gene B encodes an enzyme that converts part of the H antigens into B antigens. (Gene B encodes a specific glycosyltransferase that attaches a D-galactose residue to agglutinogen, resulting in agglutinogen B).

Gene 0 does not code for any enzyme.

Depending on the genotype, carbohydrate vegetation on the surface of erythrocytes will look like this:

For example, we cross parents with 1 and 4 groups and see why they cannot have a child with 1 group.

(Because a child with type 1 (00) should receive a 0 from each parent, but a parent with type 4 (AB) does not have a 0.)

Bombay Phenomenon

Occurs when a person does not form the “initial” H antigen on erythrocytes. In this case, the person will not have either A antigens or B antigens, even if the necessary enzymes are present. Well, great and mighty enzymes will come to turn H into A ... oops! but there is nothing to transform, asha no!

The original H antigen is encoded by a gene, which is not surprisingly designated H.

H - gene encoding antigen H

h - recessive gene, antigen H is not formed

Example: a person with the AA genotype must have 2 blood groups. But if he is AAhh, then his blood type will be the first, because there is nothing to make antigen A from.

This mutation was first discovered in Bombay, hence the name. In India, it occurs in one person in 10,000, in Taiwan - in one in 8,000. In Europe, hh is very rare - in one person in two hundred thousand (0.0005%).

An example of how Bombay Phenomenon #1 works: if one parent has the first blood type and the other has the second, then the child cannot have the fourth group, because neither parent has the B gene necessary for the 4th group.

And now the Bombay phenomenon:

The trick is that the first parent, despite their BB genes, does not have B antigens, because there is nothing to make them from. Therefore, despite the genetic third group, from the point of view of blood transfusion, he has the first group.

An example of the Bombay Phenomenon at work #2. If both parents have group 4, then they cannot have a child of group 1.

And now the Bombay Phenomenon

As you can see, with the Bombay phenomenon, parents with group 4 can still get a child with the first group.

Cis position A and B

In a person with blood type 4, an error may occur during crossing over ( chromosomal mutation), when both genes - both A and B - are on one chromosome, and nothing is on the other chromosome. Accordingly, the gametes of such an AB will turn out strange: in one there will be AB, and in the other - nothing.

Of course, chromosomes containing AB, and chromosomes containing nothing at all, will be culled by natural selection, because they will hardly conjugate to normal, wild-type chromosomes. In addition, in children of AAV and ABB, a gene imbalance (violation of viability, death of the embryo) can be observed. The probability of encountering a cis-AB mutation is estimated to be approximately 0.001% (0.012% of cis-AB relative to all ABs).

An example of cis-AB. If one parent has the 4th group, and the other the first, then they cannot have children of either the 1st or the 4th group.

And now the mutation:

The probability of having children shaded in gray is, of course, less - 0.001%, as agreed, and the remaining 99.999% fall on groups 2 and 3. But still, these fractions of a percent “should be taken into account in genetic counseling and forensic examination.”

The everyday life of a person with unique blood does not differ from its other classifications, with the exception of several factors:
· transfusion is a serious problem, only the same blood can be used for these purposes, while it is a universal donor and suitable for everyone;
Impossibility to establish paternity, if it happened that it is necessary to make DNA, it will not give results, since the child does not have the antigens that his parents have.

Interesting fact! In the USA, Massachusetts, there lives a family where two children have the Bombay phenomenon, only with the A-H type, such blood was diagnosed once in the Czech Republic in 1961. They cannot be donors for each other, since they have a different Rh- factor, and the transfusion of any other group, of course, is impossible. The eldest child has reached the age of majority and became a donor for himself in case of emergency, such a fate awaits him younger sister when she turns 18

There are three types of genes responsible for the blood group - A, B, and 0 (three alleles).

Every person has two blood type genes - one from the mother (A, B, or 0) and one from the father (A, B, or 0).

6 combinations are possible:

How it works (in terms of cell biochemistry)

On the surface of our red blood cells there are carbohydrates - “H antigens”, they are also “0 antigens”.(On the surface of red blood cells there are glycoproteins that have antigenic properties. They are called agglutinogens.)

The A gene codes for an enzyme that converts some of the H antigens into A antigens.(Gene A encodes a specific glycosyltransferase that adds an N-acetyl-D-galactosamine residue to an agglutinogen to form agglutinogen A).

The B gene codes for an enzyme that converts some of the H antigens into B antigens.(Gene B encodes a specific glycosyltransferase that adds a D-galactose residue to an agglutinogen to form agglutinogen B).

Gene 0 does not code for any enzyme.

Depending on the genotype, carbohydrate vegetation on the surface of erythrocytes will look like this:

For example, we cross parents with 1 and 4 groups and see why they have a child with 1 group.

(Because a child with type 1 (00) should receive a 0 from each parent, but a parent with type 4 (AB) does not have a 0.)

Bombay Phenomenon

Occurs when a person does not form the “initial” H antigen on erythrocytes. In this case, the person will not have either A antigens or B antigens, even if the necessary enzymes are present. Well, great and mighty enzymes will come to turn H into A ... oops! but there is nothing to transform, asha no!

The original H antigen is encoded by a gene, which is not surprisingly designated H.
H - gene encoding antigen H
h - recessive gene, antigen H is not formed

Example: a person with the AA genotype must have 2 blood groups. But if he is AAhh, then his blood type will be the first, because there is nothing to make antigen A from.

This mutation was first discovered in Bombay, hence the name. In India, it occurs in one person in 10,000, in Taiwan - in one in 8,000. In Europe, hh is very rare - in one person in two hundred thousand (0.0005%).

An example of the Bombay Phenomenon #1 at work: if one parent has the first blood type, and the other has the second, then the child has the fourth group, because none of the parents has the B gene necessary for group 4.

And now the Bombay phenomenon:

The trick is that the first parent, despite their BB genes, does not have B antigens, because there is nothing to make them from. Therefore, despite the genetic third group, from the point of view of blood transfusion, he has the first group.

An example of the Bombay Phenomenon at work #2. If both parents have group 4, then they cannot have a child of group 1.

And now the Bombay Phenomenon

As you can see, with the Bombay phenomenon, parents with group 4 can still get a child with the first group.

Cis position A and B

In a person with the 4th blood group, an error (chromosomal mutation) can occur during crossing over, when both genes A and B are on one chromosome, and nothing is on the other chromosome. Accordingly, the gametes of such an AB will turn out strange: in one there will be AB, and in the other - nothing.

Of course, chromosomes containing AB, and chromosomes containing nothing at all, will be culled by natural selection, because they will hardly conjugate to normal, wild-type chromosomes. In addition, in children of AAV and ABB, a gene imbalance (violation of viability, death of the embryo) can be observed. The probability of encountering a cis-AB mutation is estimated to be approximately 0.001% (0.012% of cis-AB relative to all ABs).

An example of cis-AB. If one parent has the 4th group, and the other the first, then they cannot have children of either the 1st or the 4th group.

And now the mutation:

The probability of having children shaded in gray is, of course, less - 0.001%, as agreed, and the remaining 99.999% fall on groups 2 and 3. But still, these fractions of a percent “should be taken into account in genetic counseling and forensic examination.”

If the child's blood type does not match one of the parents, this can be a real family tragedy, as the baby's father will suspect that the baby is not his own. In fact, such a phenomenon may be due to a rare genetic mutation that occurs in the European race in one person in 10 million! In science, this phenomenon is called the Bombay Phenomenon. In biology class, we were taught that a child inherits the blood type of one of the parents, but it turns out that this is not always the case. It happens that, for example, parents with the first and second blood groups, a baby is born with the third or fourth. How is this possible?

For the first time, genetics encountered a situation when a baby had a blood type that could not be inherited from its parents in 1952. The male father had I blood type, the female mother had II, and their child was born with III group blood. According to this combination is not possible. The doctor who observed the couple suggested that the father of the child did not have the first blood type, but its imitation, which arose due to some kind of genetic changes. That is, the gene structure has changed, and therefore the signs of blood.

This also applies to proteins responsible for the formation of blood groups. There are 2 of them in total - these are agglutinogens A and B located on the erythrocyte membrane. Inherited from parents, these antigens create a combination that determines one of four groups blood.

At the heart of the Bombay phenomenon is recessive epistasis. talking in simple words, under the influence of the mutation, the blood group has signs of I (0), since it does not contain agglutinogens, but in fact it is not.

How can you tell if you have the Bombay Phenomenon? Unlike the first blood group, when there are no agglutinogens A and B on erythrocytes, but there are agglutinins A and B in the blood serum, agglutinins determined by the inherited blood group are determined in individuals with the Bombay phenomenon. Although there will be no agglutinogen B on the child's erythrocytes (reminiscent of I (0) blood group), only agglutinin A will circulate in the serum. This will distinguish the blood with the Bombay phenomenon from the usual one, because normally people with group I have both agglutinins - A and B.

When a blood transfusion becomes necessary, patients with the Bombay Phenomenon should only be transfused with exactly the same blood. Finding it, for obvious reasons, is unrealistic, so people with this phenomenon, as a rule, save their own material at blood transfusion stations in order to use it if necessary.

If you are the owner of such rare blood, when you get married, be sure to tell your spouse about it, and when you decide to have offspring, consult a geneticist. In most cases, people with the Bombay phenomenon give birth to children with the usual blood type, but not according to the rules of inheritance recognized by science.

Photos from open sources

We know from school that there are four main blood types. The first three are common, while the fourth is rare. Classification of groups occurs according to the content of agglutinogens in the blood, which form antibodies. However, few people know that there is a fifth group, called the "Bombay Phenomenon".

To understand what is at stake, you should remember the content of antigens in the blood. So, the second group contains antigen A, the third - B, the fourth contains antigens A and B, and in the first group these elements are absent, but it contains antigen H - this is a substance that takes part in the construction of other antigens. In the fifth group there is neither A, nor B, nor H.

Inheritance

Blood type determines heredity. If the parents have the third and second groups, then their children can be born with any of the four groups, if the parents have the first group, then the children will have only the blood of the first group. However, there are times when parents give birth to children with an unusual, fifth group or Bombay phenomenon. There are no A and B antigens in this blood, which is why it is often confused with the first group. But in Bombay blood there is no H antigen contained in the first group. If a child has a Bombay phenomenon, then it will not be possible to accurately determine paternity, since there is not a single antigen in the blood that his parents have.

Discovery history

The discovery of an unusual blood group was made in 1952, in India, in the Bombay region. During malaria, mass blood tests were carried out. During the examinations, several people were identified whose blood does not belong to any of the four known groups, since it did not contain antigens. These cases have come to be known as the "Bombay Phenomenon". Later, information about such blood began to appear around the world, and in the world for every 250,000 people, one has a fifth group. In India, this figure is higher - one per 7,600 people.

According to scientists, the emergence of a new group in India is due to the fact that closely related marriages are allowed in this country. According to the laws of India, the continuation of the family within the caste allows you to save a position in society and family wealth.

What's next

After the discovery of the Bombay phenomenon, scientists at the University of Vermont made a statement that there were other rare blood types. The latest discoveries were named Langereis and Junior. These species contain previously completely unknown proteins that are responsible for the blood type.

The uniqueness of the 5th group

The most common and oldest is the first group. It originated in the time of the Neanderthals - it is more than 40 thousand years old. Almost half of the world's population has the first blood group.

The second group appeared about 15 thousand years ago. It is also not considered rare, but according to various sources, about 35% of people are its carriers. Most often, the second group is found in Japan, Western Europe.

The third group is less common. Its carriers are about 15% of the population. Most people with this group are found in Eastern Europe.

Until recently, the fourth group was considered the newest. About five thousand years have passed since its appearance. It occurs in 5% of the world's population.

The Bombay Phenomenon (blood type V) is considered the newest, having been discovered decades ago. There are only 0.001% of people on the entire planet with such a group.

The formation of the phenomenon

The classification of blood groups is based on the content of antigens. This information is used in blood transfusion. It is believed that the antigen H contained in the first group is the "progenitor" of all existing groups, since it is a kind of building material from which antigens A and B appeared.

laying chemical composition blood occurs still in utero and depends on the blood groups of the parents. And here, geneticists can say with what possible groups a baby can be born with simple calculations. Sometimes, nevertheless, deviations from the usual norm occur, and then children are born who show recessive epistasis (the Bombay phenomenon). There are no antigens A, B, H in their blood. This is the uniqueness of the fifth blood group.

People with the fifth group

These people live like millions of others, with other groups. Although they have some difficulties:

1. It is difficult to find a donor. If it is necessary to make a blood transfusion, only the fifth group can be used. However, Bombay blood can be used for all groups without exception, and there are no consequences.
2. Paternity cannot be established. If you need to do a DNA test for paternity, then it will not give any results, since the child will not have the antigens that his parents have.

There is a family in the USA in which two children were born with the Bombay phenomenon, and even with A-H type. Such blood was detected once in the Czech Republic in 1961. There are no donors for children in the world, and transfusion of other groups is fatal for them. Because of this feature, the eldest child became a donor for himself, and his sister is waiting for the same.

Biochemistry

It is generally accepted that there are three types of genes responsible for blood types: A, B and 0. Each person has two genes - one receives from the mother, and the second from the father. Based on this, there are six gene variations that determine the blood type:

1. The first group is characterized by the presence of 00 genes.
2. For the second group - AA and A0.
3. The third contains antigens 0B and BB.
4. In the fourth - AB.

Carbohydrates are located on the surface of red blood cells, they are also antigens 0 or antigens H. Under the influence of certain enzymes, the coding of the antigen H into A occurs. The same thing happens when the coding of the antigen H into B. Gene 0 does not produce any encoding of the enzyme. When there is no synthesis of agglutinogens on the surface of erythrocytes, i.e., there is no initial H antigen on the surface, then this blood is considered Bombay. Its peculiarity is that in the absence of the H antigen, or " source code”, there is nothing to convert into other antigens. In other cases, various antigens are found on the surface of erythrocytes: the first group is characterized by the absence of antigens, but the presence of H, for the second - A, for the third - B, for the fourth - AB. People with the fifth group do not have any genes on the surface of erythrocytes, and they don’t even have H, which is responsible for coding, even if there are enzymes that encode, it is impossible to turn H into another gene, because there is no H source.

The original H antigen is encoded by a gene called H. It looks like this: H is the gene that encodes the H antigen, h is a recessive gene in which the H antigen is not formed. As a result, when conducting a genetic analysis of the possible inheritance of blood groups in parents, children with a different group may be born. For example, parents with the fourth group cannot have children with the first group, but if one of the parents has a Bombay phenomenon, then they can have children with any group, even with the first.

Conclusion

Over the course of many millions of years, evolution takes place, and not only of our planet. All living beings change. Evolution did not leave blood either. This fluid not only allows us to live, but also protects us from negative impacts. environment, viruses and infections, neutralizing them and preventing them from penetrating into vital systems and organs. Similar discoveries made decades ago by scientists in the form of the Bombay phenomenon, as well as other types of blood types, remain a mystery. And it is not known how many secrets not yet revealed by scientists are kept in the blood of people around the world. Maybe after a while it will become known about another phenomenal discovery of a new group that will be very new, unique, and people with it will have incredible abilities.

In medicine, four blood groups are described in detail. All of them differ in the location of agglutinins on the surface of erythrocytes. This property is encoded genetically with the help of proteins A, B and H. Bombay syndrome is very rarely recorded in humans. This anomaly is characterized by the presence of the fifth blood group. In patients with the phenomenon, there are no proteins that are determined in the norm. The feature is formed at the stage of intrauterine development, that is, it has a genetic nature. This characteristic of the main fluid of the body is rare and does not exceed one case in ten million.

5 blood type or the history of the Bombay phenomenon

This feature was discovered and described not so long ago, in 1952. The first cases of the absence of antigens A, B and H in humans were registered in India. It is here that the percentage of the population with an anomaly is the highest and is 1 case in 7600. The discovery of Bombay syndrome, that is, a rare blood type, occurred as a result of studying fluid samples using mass spectrometry. Analyzes were made because of the epidemic in the country of such a disease as malaria. The name of the defect was in honor of the Indian city.

Bombay blood theories

Presumably, the anomaly was formed against the background of frequent related marriages. They are common in India due to social customs. Incest has not only increased the prevalence genetic diseases, but to the emergence of Bombay syndrome. This feature is currently found in only 0.0001% of the world's population. A rare characteristic of the main fluid in the human body may remain unrecognized due to imperfection modern methods diagnostics.

Development mechanism

In total, four blood types are described in detail in medicine. This division is based on the location of agglutinins on the surface of erythrocytes. Outwardly, these characteristics do not appear in any way. However, they need to be known in order to carry out a blood transfusion from one person to another. If the groups do not match, reactions can occur that can lead to the death of the patient.

This phenomenon is completely determined by the chromosome set of parents, that is, it has a hereditary character. The laying occurs at the stage of intrauterine development. For example, if the father has the first blood type, and the mother has the fourth, then the child will have a second or third. This characteristic is due to combinations of antigens A, B and H. Bombay syndrome occurs against the background of recessive epistasis - a non-allelic interaction. This is what causes the absence of blood proteins.

Features of life and problems with paternity

The presence of this anomaly does not affect human health in any way. A child or adult may not be aware of the presence of a unique feature of the body. Difficulties arise only if the patient needs a blood transfusion. Such people are universal donors. This means that their liquid will suit everyone. However, when defining Bombay syndrome, the patient will need the same unique group. Otherwise, the patient will face incompatibility, which will mean a threat to life and health.

Another problem is the confirmation of paternity. The procedure in people with this blood type is difficult. The determination of family ties is based on the detection of relevant proteins that are not detected when the patient has Bombay syndrome. Therefore, in doubtful situations, more difficult genetic tests will be required.

AT modern medicine no pathologies associated with a rare blood type have been described. Perhaps this feature is caused by the low prevalence of Bombay syndrome. It is assumed that many patients with the phenomenon are unaware of its presence. However, a rare case has been described hemolytic disease in a newborn baby whose mother had the fifth blood group. The diagnosis was confirmed on the basis of the results of the screening of antibodies, the study of lectins and the determination of the location of agglutinins on the surface of the erythrocytes of the mother and child.

Pathology diagnosed in a patient is accompanied by life-threatening processes. These features are associated with the incompatibility of the blood of the parent and fetus. At the same time, two patients suffer from the disease at once. In the described case, the mother's hematocrit was only 11%, which did not allow her to become a donor for the child.

A big problem in such cases is the lack of this rare type of physiological fluid in blood banks. This is primarily due to the low prevalence of Bombay syndrome. The difficulty is also the fact that patients may not be aware of the features. At the same time, according to the available data, many people with the fifth group willingly agree to be donors, since they realize the importance of creating a blood bank. In hemolytic disease of the newborn against the background of the diagnosis of Bombay syndrome in the mother, the cases of which are rare, there is also the possibility conservative treatment without the use of blood transfusion. The effectiveness of such therapy depends on the severity pathological changes in the mother and child.

The Importance of Unique Blood

The anomaly is considered poorly understood. Therefore, it is too early to talk about the impact of the feature on the health of the planet's population and medicine. It is indisputable that the occurrence of the Bombay syndrome complicates the already difficult procedure of blood transfusion. The presence of a 5th blood group in a person endangers life and health when a transfusion becomes necessary. At the same time, a number of scientists are inclined to believe that such an evolutionary event may have a beneficial effect in the future, since such a structure of the biological fluid is considered perfect in comparison with other common options.