Lecture 21 Flashcards
(24 cards)
What is autoimmunity?
response to self antigens that lead to tissue damage and disease
what is xenoimmunity?
responses associated with the microbiota
What is alloimmunity?
responses to nonself antigens on transplanted organs
What could cause autoimmunity during lymphocyte development?
- lack of AIRE TF
- recall: AIRE activates tissue-specific proteins that promote self-tolerance
- w/o AIRE expressed by mTECs, T cells can escape negative selection
- causes APECED
What do IL-10 and TGF-beta cytokines produced by Treg cells do?
inhibit other self-reactive T cells
what are examples of organ-specific autoimmune diseases?
- type 1 diabetes
- MS
- Crohn’s
- Graves’
- Psoriasis
What are examples of systemic autoimmune diseases?
- rheumatoid arthritis
- Scleroderma
- Systemic Lupus
What type of selection do genetic and envrionmental factors affect?
negative selection
How do autoreactive T cells affect B cells?
activate B cells which then produce autoantibodies
What is molecular mimicry?
when similarities btwn foreign and self-antigens favor autoreactive T- or B- cell activation
What happens in Graves’ disease?
- an autoimmune B cell makes antibodies against TSH receptor that also stimulate thyroid hormone production
- thyroid hormones shut down TSH production but have no effect on autoantibody production which continues to cause excessive thyroid hormone production
What happens during Myasthenia gravis?
acetylcholine receptors are internalized and degraded at neuromuscular junctions due to autoimmunity which causes the muscle to be unresponsive to acetylcholine (no muscle contraction)
What is Systemic Lupus Erythematosus?
- nucleic acid-containing immune complexes generated from dying cells activate plasmacytoid DCs to produce IFN-a
- IFN-a stimulates myeloid cells to produce BAFF which enhances survival and autoantibody production of autoreactive B cells
What is Type I Diabetes Mellitus?
- an effector T cell recognizes peptides from a cell-specific protein that produces insulin and kills the cell
- no insulin can be made
What is multiple Sclerosis?
- unknown trigger causes inflammation, attracting leukocytes into the tissue
- Autoreactive CD4 cells activate macrophages, resulting in production of pro-inflammatory cytokines and sustained inflammation
- cytokines induce production of molecules that attack tissues
What are the three treatments for autoimmune diseases?
- corticosteroids
- NSAIDs
- anti-TNFa
what are alloantigens?
- proteins expressed by graft tissue/organs which vary btwn individuals and are perceived as foreign by the recipient
- two major types are blood group Ags and histocompatibility Ags
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What are autografts?
graft between diff. sites on the same person
what is a syngenic graft?
graft btwn genetically identical people
What is an allograft?
graft btwn unrelated individuals (higher rejection rate)
What is transplant rejection primarily mediated by?
T-cell responses to MHC molecules
Does complete matching at the MHC locus ensure graft survival? why or why not?
- no.
- MHC-identical graft rejection is caused by peptides from alloantigens bound to graft MHC molecules - minor histocompatibility Ags
How does the direct transplant rejection mechanism work?
- donor dendritic cells migrate to lymph node and spleen and activate host T cells
- host effector T cells migrate to graft and destroy it
