topic 20 Flashcards
What is recognized in transplanted tissues?
Self MHC restricted T cell can recognize the foreign MHC and have it look like self MHC + protein complex. It can also recognize an actual foreign MHC + protein complex.
What is direct allorecognition?
Recipient T cell recognizes unprocessed allogeneic MHC on donor APCs
What is indirect allorecognition?
Protein from donor organ MHC is taken up into recipient APC and put on recipient MHC and presented to T cell.
What is hyperacute rejection?
Immediate. Preformed circulating Antibodies. Endothelial cells. Avoided due to HLA typing. Complement system leading to endothelial destruction and thrombosis.
What is acute rejection?
Days or weeks. CTLs or Ths. Abs lead to vascular destruction through complement system by classical pathway.
Avoided due to immunosuppressive therapy.
What is chronic rejection?
Months or years, progessive loss of graft function. Fibrosis of graft, graft arteriosclerosis. T cells.
Refractory to most therapies.
What is hematopoetic stem cell transplantation?
Hematopoietic stem cell transplantation is being used increasingly to correct hematopoietic defects, to restore bone marrow cells damaged by irradiation and chemotherapy for cancer, and to treat leukemias.
Either bone marrow cells or, more often, hematopoietic stem cells mobilized in a donor’s blood are injected into the circulation of a recipient, and the cells home to the marrow. The transplantation of hematopoietic stem cells poses many special problems.
Before transplantation, some of the bone marrow of the recipient has to be destroyed to create space to receive the transplanted stem cells, and this depletion of the recipient’s marrow inevitably causes deficiency of blood cells, including immune cells.
The immune system reacts strongly against allogeneic hematopoietic stem cells, so successful transplantation requires careful HLA matching of donor and recipient. If mature allogeneic T cells are transplanted with the stem cells, these mature T cells can attack the recipient’s tissues, resulting in a serious clinical reaction called graft-versus-host disease. Since HLA matching is always done for these transplants, this reaction is likely directed against minor histocompatibility antigens.
What are some immunosuppressive treatments for transplants?
Cyclosporine, Rapamycin, corticosteroids which are aimed at suppressing immune system (inflammation, etc.).
Specific antibodies which work by blocking t cell response.
