Autoimmunity Flashcards
Tolerance
- a state of unresponsiveness to an antigen
- usually refers to tolerance of self-antigens
- 2 types: central and peripheral
What percentage of thymocytes (immature, “baby” T cells) that enter the thymus make it through the selection processes?
- only 2 - 4%!
- this ensures that no lymphocytes sensitive to self-antigens enter the rest of the body (of course, some do)
What is Sympathetic Ophtalmia? What category of autoimmunity does it fall under?
- loss of sequestration
- trauma to the eye results in the loss of sequestration; eye antigens are free to roam the body, enter lymph nodes and elicit an immune response against the eye
Which sites are “immunological privileged sites”?
- the eyes, brain, testes, uterus/fetus
- these sites can be targeted by the immune system via loss of sequestration
What are three general categories/mechanisms of autoimmunity?
- loss of sequestration
- molecular mimicry
- conversion of normal cells into APCs
Give an example of when a normal cell can be converted into an APC via inappropriate expression of MHC class II.
- during a viral infection, certain IFN receptors can cause thyroid epithelial cells to express MHC class II
- these cells will then present their own antigens to T cells, eliciting an autoimmune response
During a viral infection, certain ____ receptors can cause ___________ cells to express MHC class II.
- IFN receptors
- thyroid epithelial cells
Acute Rheumatic Fever
- a result of molecular mimicry
- group A beta-hemolytic streptococci
- affects the heart, nervous, and musculoskeletal systems
Grave’s Disease
- antibodies target TSH (thyroid-stimulating hormone) receptors and act as agonists = hyperthyroidism
Myasthenia Gravis
- antibodies target ACh receptors at neuromuscular junctions and act as antagonists = inability to contract muscles
Which type of autoimmune diseases can be transferred in utero?
- antibody mediated autoimmune diseases
Systemic Lupus Erythematosus (SLE)
- immune complex mediated
- antibodies target cellular components (mainly in the joints, kidneys, and heart); deposition results in inflammation of these areas
- associated with a “butterfly rash”
SLE most commonly affects which regions of the body?
- the joints, the kidneys, and the heart
IDDM (Insulin-Dependent Diabetes Mellitus)
- (AKA type I diabetes)
- T-cell mediated destruction of the insulin-producing beta cells of the pancreas (islet of Langerhaans)
Rheumatoid Arthritis
- the most common rheumatic disease
- antibodies against antibodies (!) are formed and deposit in the joints
