Tolerance, Autoimmunity, and Transplantation Flashcards
Tolerance:
The immune system’s ability to recognize and ignore self-antigens to prevent autoimmune diseases.
Self-tolerance:
The process by which immune cells are educated to not react against the body’s own tissues.
Central tolerance:
Occurs in primary lymphoid organs (thymus for T cells, bone marrow for B cells) where cells that strongly react with self-antigens are eliminated.
Peripheral tolerance:
Occurs outside primary lymphoid organs and involves mechanisms like regulatory T cells (Tregs) that suppress autoreactive immune cells.
Autoimmunity:
A condition where the immune system mistakenly attacks the body’s own tissues due to a breakdown in self-tolerance.
Examples of autoimmune diseases:
Type 1 diabetes, rheumatoid arthritis, multiple sclerosis, lupus, and Hashimoto’s thyroiditis.
Molecular mimicry:
When foreign antigens resemble self-antigens, triggering an autoimmune response (e.g., rheumatic fever after a streptococcal infection).
Regulatory T cells (Tregs):
T cells that help maintain tolerance by suppressing other immune cells that could potentially attack self-tissues.
Autoantibodies:
Antibodies produced by the immune system that mistakenly target and damage the body’s own tissues.
Th17 cells in autoimmunity:
A subset of helper T cells that can contribute to autoimmune inflammation, particularly in conditions like multiple sclerosis.
Immunological tolerance and vaccines:
Vaccines must avoid breaking tolerance to self-antigens while stimulating immunity to pathogens.
Transplantation tolerance:
The ability of the immune system to accept a transplanted organ without rejection.
Alloreactivity:
The immune response to transplanted tissue, where the recipient’s immune system targets the donor’s MHC molecules as foreign.
Graft rejection:
The immune system’s response against a transplanted organ or tissue, mediated by T cells and antibodies.
Hyperacute rejection:
A rapid immune response against a transplanted organ that occurs within minutes to hours, usually due to pre-existing antibodies.
Acute rejection:
A more gradual immune response (days to months) where T cells attack the transplanted organ or tissue.
Chronic rejection:
A long-term immune response that slowly damages the transplanted tissue over time, often leading to organ failure.
Immunosuppressive drugs:
Medications that suppress the immune system to prevent graft rejection, often used after organ transplantation.
HLA mismatch:
The differences in human leukocyte antigens (HLA) between donor and recipient that contribute to graft rejection.
Bone marrow transplantation:
A procedure to replace damaged or diseased bone marrow with healthy marrow, often used to treat leukemia or other blood disorders.
Graft-versus-host disease (GVHD):
A complication of bone marrow transplantation where the donated immune cells attack the recipient’s tissues.
Induction immunosuppression:
Intense immunosuppression used immediately after transplantation to prevent rejection, typically with monoclonal antibodies or high-dose steroids.
Maintenance immunosuppression:
Ongoing immunosuppressive therapy to prevent chronic rejection after organ transplantation.
Tolerance induction in transplantation:
Strategies to promote long-term acceptance of a transplant without the need for lifelong immunosuppressive therapy.
T cell tolerance in transplantation:
T cells that recognize donor antigens must become tolerant to prevent graft rejection.
Donor-specific transfusion (DST):
A technique used to induce immune tolerance in transplant recipients by exposing them to donor cells before transplantation.
Crossmatch test:
A test performed before organ transplantation to ensure that the recipient’s immune system will not attack the donor organ.
Molecular tolerance in transplantation:
The idea of inducing tolerance to the transplant at the molecular level by modulating immune responses, such as through regulatory T cells.
Tolerance and autoimmune diseases:
Breakdown of immune tolerance leads to autoimmune diseases, where self-reactive immune cells attack the body’s own tissues.
Immune checkpoint inhibitors and autoimmunity:
Checkpoint inhibitors used in cancer therapy can enhance immune responses, but may lead to autoimmune reactions in some cases.
Hematopoietic stem cell transplantation (HSCT):
The transplantation of hematopoietic stem cells to restore the blood and immune systems, often used for blood cancers.
