1)-What is the main purpose of bone marrow transplantation? Why is graft versus

Question

1)-What is the main purpose of bone marrow transplantation? Why is graft versus host (GVH) disease a concern in bone marrow transplantation? How could GVH be prevented?

2-High polymorphism in MHC (HLA in humans) is important in the human species' protective immune response, but poses a mojor challenge in donaor-recipient matching during organ/tissue transplantation. It is estimated that enormous number of T cell clones in an individual-up to 5%-could be activated in response to foreign HLA molecules ( alloantigens of another individual). Briefly, discuss the mechanisms of HLA alloantigen recognition by T cells which could contribute to this unusually high-response phenomenon.

Explanation / Answer

1 PURPOSE: Bone marrow transplants aims to replace damaged stem cells with healthy cell, thus body is able to make enough WBC's, platelet cells and RBC's

GVHD ( Graft versus host disease) occurs after bone marrow/stem cell transplant, where one receives the bone marrow tissue or cells from a donor. In this case the cells attack the receipients body.

GVHD can be prevented by getting the best donor match for a bone marrow or stem cell transplant. Further medication help prevent GVHD, and protecting oneself from UV rays that increases risk of developing GVHD

2. T cells recognise alloantigens by either direct or indirect alloantigen recognition. This leads to transplant rejection after organ transplant.

Direct alloantigen recognition: In this case donor tissue dendritic cell migrate to the lymph node, stimulates T cells. The host cells there recognise either the allograft HLA or associated bound peptide. Thus alloreactive T cells get stimulated by donor APCs

Indirect alloantigen recognition: Here host dendritic cells process proteins from the transplant graft and trigger T cells. Presentation can occur via MHC class I or MHC class II. Thus in direct alloantigen , dendritic cells are derived from donor and in indirect the dendritic cells (APCs) involved are those of recipient.

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