The patient or donor cells differentiate and self renew to reestablish complete hematopoiesis

I'm not sure I understand your question. Are you talking about graft vs host reaction?

Do you mean regenerate? Irradiation of chemotherapy has a two-fold use, not only destroying current resident cancerous cells but to "make space" for newly transplanted BM cells. Once the BM or stem cells are transplanted into the peripheral blood of the patient, them home to the bone marrow, which is a low oxygen niche, preserving their senescence and function to include years of gradual bone marrow production.

I think you've meant - "regenerate". Just as Michael Dugan answered, after the myeloablation, the new primitive hematopoietic precursor cells (hematopoietic stem cells) are transplanted into the patient. These cells are capable to self-renewal, differentiation into all types of blood cells, and short-/long-term repopulation of hematopoietic system.

I do not know if I got the point. However, if the hematological disease reappears after BMT it is not due to d'onore HSCs but it depends on the fact that you were not able to heradicate the clone. In this view, leukemic HSCs escape the immunosurveillance of donor HSCs and the disease reelapse.

The donor cells move into the bone marrow and grow to become active blood cells. The goal is for the patient's bone marrow cells not to regrow at all.

what do you mean by the term "degenerate" in your question ? it is NOT clear?are you asking about- ALLO or AUTO Tx? The idea of Allo Tx is to have best matched stem cells from BM or peripheral blood source of a normal non cancerous donor engraft into the host (patient that has its cancerous cells and its body immune system eliminated or ablated with irradiation, chemotherapy and or immune suppressive drugs.). The chimerism or engraftment process in allogeneic SC Tx is certainly not perfect and the "systemic degenerative" damage of Graft versus Host reaction causes horrible suffering and infection. The hope of BMT is to restore the hemopoietic system in bone marrow. Depending on the leukemia stage the malignant precursor clones can fight back and relapse may destroy or degenerate the bone of the host, but this is mostly a problem in elderly patients (>65 yrs). Young people with leukemia, if diagnosed early enough can restore a functional immune system and not only survive but also thrive with good Qualtiy of life (QoL) after BMT or alloSCT.

Because transplantation occurs AFTER the patient's normal and cancerous cells are destroyed.

Do you mean autologous are allogeneic bone marrow transplantation? In both cases the recipient's bone marrow is pre-treated with a therapeutic antibody such as anti-CD20 or anti-CD52. The former antibody will eliminate all B cells (including the tumour cells) apart from terminally differentiated B cells and stem cells whereas anti-CD52 will attack the tumour cells and the majority of haematopoeitic cells again with the exception of hopefully the normal stem cells. Thus the patient's own stem cells will be left after treatment to regenerate their bone marrow. This is the situation in the case of autologous transplantation when the patient's own bone marrow will have been harvested at remission, treated with antibodies and used in subsequent transplantation. In the case of allogeneic transplants then the donor's cells will not have been treated antibodies since they do not contain any tumour cells and so when transplanted can colonise the recipient's bone marrow. The greatest risk in this case is rejection of the donor cells by the recipient's regenerating bone marrow cells but this approach has the advantage of a donor versus tumour immune response to help prevent relapse..

HSCs home to their niches and then start regenerating the normal hematopoietic tissue. If I understood your question correctly, you are asking whether the hematopoietic niche is altered by the conditioning regimen and if so, how can the recovery process occur. One possible explanation is that, in the post-BMT setting, HSCs could tend to colonize also those niches that are not normally used during normal hematopoiesis, i.e. those in the long bones shafts, thus extending the regenerative process and helping recovery.

I am not sure I understand the question. Not ALL the normal cells are destroyed in the body but the goal certainly is to destroy EVERYTHING in the marrow. The grafted stem cells are pluripotent and home to marrow where they set up normal hematopoiesis. In autologous transplants the cancer eradication is achieved by conditioning regimen, while in Allogeneic transplants conditioning regimens are helped by what is called Graft versus Leukemia/Lymphoma effect where engrafted stem cells lead to donor type immune system (primarily T cell is important) which fights the cancer cells to prevent relapse. This GVL depends upon the closeness of HLA match and is also important in Graft versus Host disease.

Hi,

The wrong assumption is that chemo/radiotherapy kills all host cells. It is a stochastic event - you are never sure that it occurs completely. To be sure, you should use a dose that will be toxic not only to bone marrow but also to gut and other tissues. If you mean relapse (degenerate??) it can occur because of incomplete destruction of host malignant hematopoiesis.

Previous answers cover the subject quite well and I have nothing new to add.

I agree with Konstantin Levay answer that the new hematopoitic cells differentiate into all types of blood cells.

Hi

Your question is not so clear, but usually BMT had been done in patients with malignant (such as leukemia) or non-malignant (such as talathemia) hematopoietic disorders.

In these cases, before BMT, the patient receive aggressive chemotherapy for destroy malignant cell, and replace BM cells by donor cells (own [autologous], related or unrelated [allogeneic]). The normal HSC of donor will responsible to generate all blood linage (RBC, WBC, and platelet). Near the 50% of transplantation will successes and other unfortunately will rejected during 5 years.

I meant regeneration .thank to all.......................................giving me an idea of bone marrow transplantation...thank youuuuuuuu

The comment made above by Ludek Sefc is very true. We cannot assume with absolute certainty that chemo and radiotherapy has eliminated ALL tumor cells prior to transfusion of the graft cells.

The allo-immune response of graft cells against the host cells is an integral component of the anti-tumor therapy.

Indeed, the 'mass destruction' caused by the chemo and radiotherapy prior to the transplant do not make life easy for the new cells on their mission to engraft in the host.

Hematopoietic stem cells do not cause bone marrow cells to degenerate.

Either the stem cells are retrieved before ablation and stored and again transplanted (autologous) or the donor stem cells are transplanted onto the prepared (as you mentioned) recipient marrow (allogenic).

You are asking why the transplanted stem cell degenerate, you asking what the mechanism of graft failure? Many reasons for graft to fail, defective stem cells, not enough immune suppression and host immunity rejects the graft, poor choice of donors, not enough collection etc.