Before donating hematopoietic stem cells, you need to undergo typing (determination of the HLA genotype) of the bone marrow. And if you match the type of any patient, you will be invited to donate hematopoietic stem cells.

What is a bone marrow transplant?

Bone marrow transplantation actually refers to the transplantation of hematopoietic stem cells. Hematopoietic (hematopoietic) stem cells are formed in the human bone marrow and are the ancestors of all blood cells: leukocytes, erythrocytes and platelets.

Who needs a bone marrow transplant?

For many patients with oncological and hematological diseases, the only chance to save a life is a hematopoietic stem cell transplant. This could save the lives of thousands of children and adults with cancer, leukemia, lymphoma or hereditary diseases.

Who can become a hematopoietic cell donor?

Any healthy citizen of the Russian Federation without chronic diseases aged 18 to 45 years.

An important factor for bone marrow donation is age: the younger the donor, the higher the concentration of hematopoietic stem cells in the transplant and their "quality".

How is bone marrow typing done?

To determine the HLA genotype (typing), 1 tube of blood will be taken from you. A blood sample (up to 10 ml - as in a regular blood test) of a person who wants to become a donor of hematopoietic stem cells is examined in a specialized laboratory.

Information about the results of typing of donors recruited and HLA-typed at the National Research Center for Hematology of the Ministry of Health of Russia is entered into the all-Russian database of donors - the National Register of Bone Marrow Donors.

The typing procedure requires only a little time from the donor, does not require any costs and does not differ from a regular blood test.

What happens after the data is entered into the register?

When a patient appears who needs to undergo bone marrow transplantation, his HLA genotype data is compared with the data of potential donors available in the registry. As a result, one or more "matched" donors can be matched. The potential donor is informed about this, and he decides whether or not to become a real donor. For a potential donor, the probability of becoming a real donor is no more than 1%.

According to the data of the International Bone Marrow Donor Association (WMDA), in 2007, every 500th inhabitant of our planet was a potential donor of hematopoietic stem cells, and out of every 1430 potential donors, one donor became real, i.e., donated stem cells.

According to WMDA, in 2007 there were officially 20,933 potential unrelated stem cell donors in Russia.

According to the annual reports of the International Bone Marrow Donor Search System (BMDW), Russia ranks fourth in the frequency of rare HLA donor phenotypes, behind only Mexico, Argentina and South Africa. It follows from this that it is obviously impossible to find compatible donors for all Russian patients in need of bone marrow transplantation in foreign registries (in particular, European ones).

This implies the importance of replenishing the domestic bone marrow registry. The more people are typed for the Register, the more lives can be saved.

The chance of finding a donor for a patient with a common HLA genotype is 1 in 10,000, i.e., it is likely that one in 10,000 donors will be compatible with the patient.

How is the procedure for donating stem cells?

If you matched the HLA genotype to some patient and you have to become a bone marrow donor, then do not be afraid! Obtaining stem cells from peripheral blood is a simple, comfortable and safe procedure for the donor.

Donor bone marrow is taken in one of two ways:

• a syringe from the pelvic bone (the procedure is painless under anesthesia),
• with the help of a medical preparation, bone marrow cells are “expelled” into the blood and collected from there through a peripheral vein.

This procedure is similar to hardware plateletpheresis (platelet donation procedure), but longer in time.

The donor donates only a small part of his bone marrow.

Today, the process of stem cell transplantation is the most effective method of treating oncological, hereditary, hematological, autoimmune diseases in both adults and children. This article will be devoted to this issue.

Hematopoietic stem cells and their transplantation

Many people do not connect such concepts as stem cells and bone marrow transplantation in any way, but they are closely interconnected. After all, this way of donation is a transplant. They multiply quickly and produce healthy offspring. Hematopoietic cells are the precursors of blood and human immunity. Stem cells transplanted to the patient restore the body's hematopoiesis, increase resistance to viruses. There is no other way to receive these cells other than to become a bone marrow donor. The source can be different tissues of the human body.

Where are these cells located?

We have stem cells in the hematopoietic substance that is in the bones. Most of all it is observed in the pelvic, breast bones, spine. For a long time, hematopoietic stem cells were formed only in the bone marrow. For this reason, most foreign registers have the same name. They are called bone marrow donors.

In the 1990s, it was scientifically proven that, thanks to the introduction of special preparations into the human body, it is possible to bring stem cells out of the place of their formation into the blood stream for a short time, and extract them from it using special equipment.

What else do you need to pay attention to before becoming a bone marrow donor? More than ten years ago, a bank was established in Samara on the basis of the Clinical Center for Cellular Technologies. They learned to receive in a different way.

Where to find a donor?

Unfortunately, in Russia such programs are in their infancy. There is no full-fledged register and state support. Measures to create this base for transplantation are gradually beginning to be introduced. Every year there are more and more donors. To increase the number of volunteers, it is important to inform the population, conduct training seminars and lectures.

When a disaster strikes in the family and the relatives want to help the patient, they soon face the question of how to become a bone marrow donor. After all, it is he who needs to be transplanted to a loved one. But they are not always able to help in this matter, since only about 30% of loved ones have full stem cell compatibility. The ideal option is bone marrow transplantation from a twin, but these are isolated cases.

If there is no compatibility among close people, then it is necessary to resort to the help of the database of bone marrow donors in our country. But their number is negligible. Therefore, the next step in the search for donors is to turn to foreign registries. But it is important to understand that this is a very expensive procedure, the cost of which is equal to several tens of thousands of euros.

Many countries are actively working to expand unrelated donor lists of hematopoietic stem cells. This is due to the spread of diseases that can only be cured in this way. Currently, there are about sixty bases, which are combined into a common world base. The total number of possible donors is approximately 20,000,000 people. Thanks to such international registries, it is possible to find a suitable option for 60-80% of sick patients. And how to become a bone marrow donor and a member of the global database, we will learn a little lower.

Creation of a registry of bone marrow hematopoietic cell donors in Russia

In the Russian Federation, work has already begun on the creation of stem cell registries. However, the total number of tested potential donors is small, there are about two thousand people. It is clear that such a number does not allow for an effective selection of cells for all patients who need help. Therefore, we definitely need to ask ourselves the question of how to become a bone marrow donor. There is no such way of donation in Yekaterinburg. But such services exist in other cities. A small donor registry in Chelyabinsk was set up at a regional station. Potential patients are voluntarily and anonymously included in this list of data, subject to their gratuitous participation in the absence of any health contraindications.

Requirements for a bone marrow donor

Any healthy person can become a potential donor. Suitable age is 18-55 years old. He should not be sick with tuberculosis, AIDS, hepatitis B and C, malaria, cancer, mental disorders. This is the first step to becoming a bone marrow donor. In Voronezh, a bone marrow donation campaign was recently held among the residents of the city. The results of the studies were anonymously entered into a list, the so-called registry.

A volunteer donates twenty milliliters of blood at any of the transfusion stations. The blood fluid from the vein will undergo tissue typing. This is done in St. Petersburg, after these procedures all the donor's data will be entered into the Russian registry.

Donation in Nizhny Novgorod

Every year in Russia more than 1,500 people need stem cell transplantation, most of them are children. This can help patients restore blood formation and the immune system. Due to the minimum number of hematopoietic cell donors in our country, the opportunity to help these children is minimal, especially since the genotype of each person is individual, and the probability of choosing a suitable donor is 1:30,000. Therefore, Russian doctors use the foreign donor registry, but perhaps this problem will be resolved soon.

Various events are held across the country, during which people are explained how to become a bone marrow donor. In Nizhny Novgorod, such an action was very successful among students of the Linguistic University and the Academy of Water Transport. After the meeting, the register of donors of the Russian Federation increased by dozens of people who agreed to undergo this procedure.

How is bone marrow harvested?

For transplantation from a bone marrow donor, he is hospitalized for a day. This procedure must be done under general anesthesia. Before becoming a bone marrow donor, it is imperative to undergo a medical examination for the tolerance of anesthesia.

Bone marrow is taken from special wide needles. The operation can take several hours. During the intervention, only a few percent of the bone marrow is harvested. The donor is allowed to leave the clinic on the same day. Within a few days, some soreness in the bones will be felt, which can be easily removed. Full recovery of the bone marrow will occur in a two-week period.

Taking stem cells from blood

The procedure in question is practically painless. This is important for those who are interested in how to become a bone marrow donor. In Moscow, for money, there are many who want to get into the ranks of volunteers. But this procedure is free.

Within five days before sampling, the patient is injected subcutaneously with a medication that removes cells into the bloodstream. Then it is connected to a special apparatus, with which blood is taken. Subsequently, the material is split into components. The latter are delivered to the laboratory, where they are processed in a special way. Useful cells are collected in a bag, and the rest of the blood is returned to the donor. This procedure takes several hours.

Cancellation of the procedure

Entering data into the register does not oblige you to anything, since becoming a bone marrow donor in Russia or in another country is just a desire and consent to donate hematopoietic cells and save a life. The probability of compatibility of a particular donor with the patient is catastrophically small. But the more Russian donors are represented in the bone marrow registry, the higher the chance of a cure in our patients. After all, the inhabitants of the Russian Federation are genetically significantly different, for example, from Europeans and Americans.

Becoming the one who donates his bone marrow or not is a personal matter for everyone, but it is important to understand that no one is immune from diseases, and an indifferent attitude to the problem of donation can become a tragedy for all mankind in the future.

Are you between 18 and 45 years old? Have you had any serious illnesses?
Are you willing to take the time to save someone's life?
Interested in joining the bone marrow donor registry?
But don't know how to do it?

HERE'S HOW - STEP BY STEP

1. From October 1, 2018, any volunteer who decides to become a potential bone marrow donor can donate blood for typing at the nearest Invitro medical office. If there are no Invitro laboratories in your city, check out the list of the nearest donor shares. If your city is not on the list, please email [email protected] . Our staff will contact you and help organize a fundraiser in your area.

2. You sign an agreement to join the bone marrow (hematopoietic stem cell) donor registry.

3. You donate 4-9 ml of blood to determine your HLA phenotype - a set of genes responsible for tissue compatibility.

4. Your HLA phenotype is determined in the laboratory.

5. You are on the registry, you are a potential bone marrow donor. After some time, you may become a real donor, but you may never become one. It depends on whether your HLA phenotype will ever match a particular patient.

6. You will be asked to inform the registry staff about the change of residence, telephone number, changes in health status.

7. If a specific patient needs cells compatible with yours, and you confirm your consent to become a donor, you will be asked to come to the clinic, where they will tell you in detail about the procedure for harvesting hematopoietic stem cells. Before becoming a real donor, you will undergo a complete medical examination, the purpose of which is to make cell collection as safe as possible.

8. Harvesting of your hematopoietic stem cells can be done in one of the ways you choose.

Directly from the bone marrow: piercing the pelvic bone, a small part of the bone marrow will be taken from you under anesthesia using a sterile syringe; the operation will last about 30 minutes; you will spend about two days in the hospital; after the operation, you will experience pain, easily relieved by pain pills; your bone marrow will fully recover in one week to one month.

From peripheral (venous) blood: you will first be given a drug that “expels” hematopoietic cells from the bone marrow into the blood; blood will be taken from a vein in one arm, it will pass through a cell-separating device and return to a vein in the other arm; you will spend about five to six hours in an armchair, while you can read, watch TV; anesthesia is not required; your cells will fully recover within one week to one month.

9. For at least two years, your recipient will not know who became his donor.

10. You can at any time, without giving reasons, withdraw your intention to become a real donor. But before you refuse, think about the patient - the genetic "twin" with whom your HLA phenotype coincided.

In the human body, red bone marrow performs the function of blood renewal. Violations of his work entail serious diseases, the number of which is constantly growing. So there is a need for a transplant of this element of the body's system, which creates a demand for donors. The difficulty of the situation becomes finding the right person.

Types of bone marrow transplant

Previously, this procedure was not performed, but bone marrow is now being transplanted to treat or improve survival in leukemia (blood cancer), lymphoma, aplastic anemia, multiple myeloma, breast cancer, ovarian cancer. The main task of the donor is to donate hematopoietic stem cells, which become precursors in the formation of all other components of the blood. For their transplantation, there are two main types of procedures - allogeneic and autologous transplantation.

Allogeneic transplant

This type involves the sampling of bone marrow from a person that is as close as possible genetically to the patient. As a rule, they become a relative. This donor transplant option can be of two types:

1. Syngeneic - derived from an identical twin. Autotransplantation of bone marrow from such a donor implies full (absolute) compatibility, which eliminates the immune conflict.
2. In the second case, a healthy relative becomes a donor. Efficiency directly depends on the percentage of compatibility of bone marrow tissues. A 100% match is considered ideal, and with a low percentage, there is a chance that the body will reject the transplant, which is perceived by it as a tumor cell. In the same form, there is a haploidentical transplantation, in which the match has 50% and is carried out from a person with an unrelated relationship. These are the most unfortunate conditions that have a high risk of complications.

autologous

This procedure consists in the fact that pre-harvested healthy stem cells are frozen and planted in the patient after high-intensity chemotherapy. With a successful procedure, a person quickly restores the body's immune system, the process of hematopoiesis normalizes. This type of transplantation is indicated in case of remission of the disease or when the disease does not affect the bone marrow:

• with a brain tumor;
• ovarian cancer, breast cancer;
• lymphogranulomatosis;
• non-Hodgkin's lymphoma.

How to become a donor

In order to be included in the bone marrow donor registry, a person must be 18-50 years old. Other requirements: no hepatitis C and B, malaria, tuberculosis, HIV, cancer, diabetes. To be entered into the database, you must donate 9 ml of blood for typing, provide your data and sign an agreement on entering into the register. If your HLA type is compatible with any of the patients, additional testing will be required. Initially, you will need to give your consent, which will be required by law.

Some people are interested in how much donors are paid. In all countries, such activity is “anonymous, free and gratuitous”, so it is impossible to sell stem cells, they can only be donated. Sometimes you can find information with a call to find a donor to help a child with a promise of a reward. In this case, it is possible to sell the material on an individual basis, government agencies do not approve or support such transactions.

Who can be a donor

A potential donor is selected according to one of 4 options. They differ from each other, but they pursue one goal - the maximum degree of compatibility. Suitable for transplant:

1. The patient himself. His disease must be in remission or not affect the bone marrow itself. The resulting stem cells are carefully processed and frozen.
2. Identical twin. As a rule, relatives of this type have 100% compatibility.
3. Family member. Relatives have a high degree of compatibility with the patient, but this is not necessary. Brothers and sisters have a high probability of becoming a donor.
4. Not a relative. There is a Russian bone marrow donor bank. Among the donors registered there, there may be people compatible with the patient. There are similar registers in Germany, the USA, Israel and other countries with a developed medical field.

How is bone marrow taken?

Bone marrow sampling is performed in the operating room under general anesthesia to minimize the likelihood of injury and reduce discomfort. A special needle with limiters is inserted into the femur or iliac pelvic bone, where the maximum amount of material needed is. As a rule, repeated punctures are performed to obtain the desired amount of fluid. There is no need to cut the fabric or sew it up. All manipulations are carried out with a needle and syringe.

The required amount of donor bone marrow depends on the size of the patient and the concentration of stem cells in the taken substance. As a rule, 950-2000 ml of a mixture of blood and bone marrow are collected. It seems that this is a large volume, but it is only 2% of the total amount of matter in the human body. Full recovery of this loss will occur in 4 weeks.

Donors are now also being offered the apheresis procedure. To begin with, a person is injected with special drugs that stimulate the release of bone marrow into the blood. The next step is similar to plasma donation. Blood is taken from one arm, and special equipment isolates the stem cells from other components. The fluid cleared from the bone marrow returns to the human body through a vein in the other arm.

How is the transplant

Before the transfer procedure, the patient undergoes an intensive course of chemotherapy, the radical radiation necessary to destroy the diseased bone marrow. After that, pluripotent SCs are transplanted using an intravenous dropper. The procedure usually takes one hour. Once in the bloodstream, donor cells begin to take root. To speed up the process, doctors use drugs that stimulate the work of the hematopoietic organ.

Consequences for the donor

Every person, before becoming a bone marrow donor, wants to know about the consequences of the operation. Doctors note that the risks during the procedure are minimal, more often associated with the individual characteristics of the body's reaction to anesthesia or the introduction of a surgical needle. In rare cases, an infection has been reported at the puncture site. After the procedure, the donor may experience side effects:

• pain at the puncture site;
• bone pain
• nausea;
• muscle pain;
• increased fatigue;
• headache.

Contraindications

Before you become a voluntary bone marrow donor and undergo an examination, you should familiarize yourself with the list of contraindications. They largely intersect with the points on the prohibition of blood donation, for example:

• age over 55 or under 18;
• tuberculosis;
• mental disorders;
• hepatitis B, C;
• autoimmune diseases;
• malaria;
• the presence of HIV;
• oncological diseases.

Video

Bone marrow is a soft, spongy tissue found inside bones. Bone marrow contains hematopoietic or hematopoietic stem cells.

Hematopoietic stem cells can divide to create more hematopoietic stem cells or develop to create red blood cells - erythrocytes, white blood cells - leukocytes and platelets, which are responsible for blood clotting. Most hematopoietic stem cells are found in the bone marrow, although a small number are found in the umbilical cord and blood.

Cells obtained from any of the above locations can be used for transplantation.

What is a bone marrow transplant?

Bone marrow and peripheral blood stem cell transplantation is used to treat damaged stem cells using high doses of chemotherapy and/or radiation therapy.

There are three types of transplant:

Autologous transplantation - transplantation of the patient's own stem cells;

Syngeneic transplantation - the transplant is transferred from one monozygotic twin to another;

Allogeneic transplant - the transplant is taken from the patient's sibling or parent. A person who is not a relative, but is suitable for transplantation according to certain parameters, can also act as a donor.

How is a bone marrow transplant performed?

When transplanting from the patient's own body, of course, thorough treatment is required. For this reason, first, in accordance with the plan approved by the doctors, treatment will be carried out. At the next stage, stem cells will be collected, followed by freezing and treatment with special medicines. The dose of medication in such patients is higher. Usually, within a week after the collection of healthy stem cells, the patient receives high-dose drug therapy. At the end of the treatment, the patient receives healthy latent stem cells back. Thanks to this approach, stem cells, cells that were damaged during treatment, begin to repair themselves.

What are the risks of autologous transplantation?

Taking stem cells from a patient carries the risk of taking infected cells. In other words, the administration of frozen stem cells to a patient may result in a relapse of the disease due to the administration of diseased cells.

What are the risks of allogeneic transplantation?

During allogeneic transplantation, there is an exchange between the immune systems of the donor and the patient, which is an advantage. However, when performing such a transplant, there is a risk of a mismatch of immune systems. The donor's immune system can have a negative impact on the recipient's body. There is a risk of damage to the liver, skin, bone marrow and intestines. This process is called the graft-versus-host reaction. If such a reaction occurs, patients require treatment, since lesions can cause malfunctions or organ failure. With autologous transplantation, these risks are absent.

How is it determined that the donor's stem cells are compatible with the recipient's stem cells in allogeneic and syngeneic transplantation?

During transplantation, doctors use donor stem cells that match the patient's stem cells as much as possible. This is done to reduce side effects. Different people have different types of protein filaments on the surface of their cells. Such protein filaments are called human leukocyte antigen (HLA). Thanks to a blood test - HLA typing - these protein filaments are deciphered.

In most cases, the success of allogeneic transplantation depends on the degree of compatibility of the HLA antigens of the donor and recipient stem cells. The probability of accepting the donor's stem cells by the recipient's body increases with an increase in the number of compatible HLA antigens. Generally speaking, if there is a high degree of compatibility between donor and recipient stem cells, the risk of developing a complication called graft-versus-host disease (GVHD) is reduced.

The likelihood of HLA compatibility of close relatives and especially siblings is higher compared to HLA compatibility of people who are not relatives. However, only 20-25% of patients have an HLA-compatible sibling or sister. The probability of having HLA-compatible stem cells in an unrelated donor is slightly higher and is about 50%. HLA compatibility among unrelated donors increases significantly if the donor and recipient come from the same ethnic group and belong to the same race. While the number of donors is generally on the rise, some ethnic groups and races find it more difficult than others to find a suitable donor. A universal record of volunteer donors can help in finding an unrelated donor.

Monozygotic twins have the same genes and therefore the same strands of HLA antigens. As a result, the patient's body will accept the transplant of his/her monozygotic twin. However, the number of monozygotic twins is not very high, so syngeneic transplants are rarely performed.

How is bone marrow obtained for transplantation?

The stem cells used in bone marrow transplants are obtained from the fluid found inside the bones - the bone marrow. The procedure for obtaining bone marrow is called bone marrow harvesting and is the same for all three types of transplants (autologous, allogeneic, and syngeneic). A patient under general or local (expressed in numbness of the lower body) anesthesia is inserted into the pelvic bone with a needle for bone marrow sampling. The bone marrow harvesting process takes about an hour.

The resulting bone marrow is processed to remove residual bone and blood. Antiseptics are sometimes added to the bone marrow, after which it is frozen until stem cells are needed. This method is called cryopreservation. Thanks to this method, stem cells can be stored for many years.

How are peripheral blood stem cells obtained?

Peripheral blood stem cells are obtained from the bloodstream. Peripheral blood stem cells for transplantation are obtained through a procedure called apheresis or leukapheresis. 4-5 days before the apheresis, the donor receives a special drug that increases the number of stem cells in the bloodstream. Blood for apheresis is taken from a large vein in the arm or using a central venous catheter (a soft tube placed in a wide vein in the neck, chest, or pelvic area). Blood is taken under pressure using a special machine that collects stem cells. Then the blood is injected back to the donor, and the collected cells are taken away for storage. Apheresis usually takes 4 to 6 hours. The stem cells are then frozen.

Are there any risks for bone marrow donors?

Usually, donors do not have health problems, since a very small amount of bone marrow is taken. The main risk for the donor is the possibility of complications after anesthesia.

For several days, there may be swelling and compaction at the sampling sites. During this period, the donor may feel a sense of fatigue. Within a few weeks, the donor's body will restore the lost bone marrow, however, the recovery period is different for each person. While some people need 2-3 days to return to daily activities, others may need 3-4 weeks to recuperate.

Are there any risks for peripheral blood stem cell donors?

Apheresis usually causes minimal discomfort. The donor may experience weakness, trembling, numbness of the lips, and cramps in the arms. Unlike bone marrow sampling, anesthesia is not required for peripheral blood stem cell sampling. A drug used to release stem cells from bones into the bloodstream may cause bone and muscle pain, headaches, fatigue, nausea, vomiting, and/or trouble sleeping. Side effects recede 2-3 days after taking the last dose of the drug.

What happens after a stem cell transplant to a patient?

Once introduced into the bloodstream, the stem cells will settle in the bone marrow, where they will begin to produce red and white blood cells and platelets. These cells usually start producing blood within 2-4 weeks after transplantation. Doctors will monitor this process with frequent blood tests. Full recovery of the immune system, however, will take much longer. This period usually takes several months for autologous transplantation and up to 1-2 years for allogeneic and syngeneic transplants.

What are the possible side effects of a bone marrow transplant?

The main risk of treatment is increased susceptibility to infections and bleeding associated with high-dose cancer treatment. Doctors may prescribe antibiotics to patients to prevent or treat infections. A platelet transfusion may be needed to prevent bleeding, and a red blood cell transfusion may be needed to treat anemia. Patients undergoing bone marrow or peripheral blood stem cell transplantation may experience short-term side effects such as nausea, vomiting, fatigue, loss of appetite, mouth ulcers, hair loss, and skin reactions.

Possible long-term side effects usually include reactions associated with pre-transplant chemotherapy and radiation therapy. These include infertility (the biological inability of the body to conceive), cataracts (clouding of the crystal of the eye), secondary cancer, and damage to the liver, kidneys, lungs, and/or heart. The risk of complications and their severity depend on the treatment of the patient and should be discussed with the doctor.

What is a "mini transplant"?

Mini transplant is a type of allogeneic transplant (reduced intensity or non-myeloblast transplants). To date, this approach is being investigated clinically and is aimed at treating various forms of cancer, including leukemia, multiple myeloma, and other forms of blood cancer.

In a mini-transplant, less intensive, low-dose chemotherapy and/or radiation therapy is used to prepare the patient for an allogeneic transplant. The use of small doses of anti-cancer drugs and radiation only partially destroys the bone marrow, and does not damage it completely, and also reduces pure cancer cells and suppresses the immune system in order to prevent transplant rejection.

Unlike traditional bone marrow or peripheral blood stem cell transplantation, after mini-transplantation, both donor and recipient cells continue to exist for some time. When the bone marrow begins to produce blood, the donor's cells enter into a graft-versus-tumor reaction and begin to destroy the cancer cells left behind by anti-cancer drugs and/or radiation therapy. To increase the graft-versus-tumor effect, donor white blood cells may be injected into the patient. This procedure is called “donor lymphocyte infusion”.