17: Autoimmunity Flashcards
Autoimmunity
Immune response directed at “self” antigens/tissues
What are the effectors of autoimmune responses?
Autoantibodies and autoimmune T cells
The classes of autoimmune disease are defined by _______.
The immunological effector that causes the disease
T or F: Autoimmune diseases are usually mediated by IgE antibodies.
F: Nevaaaaaa
What goes wrong in the immune system that causes autoimmune disease?
The negative selection process that removes self-reactive B cells and T cells from the lymphocyte repertoire breaks down
Type II autoimmune diseases are caused by __________.
Antibodies specific for components of cell surfaces or the ECM
What are 5 mechanisms that contribute to immunological self-tolerance?
- Negative selection in bone marrow and thymus
- Expression of tissue-specific proteins in the thymus
- No lymphocyte access to some tissues
- Suppression of autoimmune responses by regulatory T cells
- Induction of anergy in auto reactive B and T cells
What causes autoimmune hemolytic anemia?
IgG and IgM antibodies specific for surface antigens of erythrocytes
What happens in autoimmune hemolytic anemia?
- Activation of the classical complement pathway, and MAC destroys the RBCs
- Bound Ab and C3b mediate clearance of RBCs from circulation by phagocytes in the spleen
- Destruction of RBCs –> anemia
What test is used to confirm autoimmune hemolytic anemia?
Direct Coomb’s hemagglutination test
Patients that have autoimmune responses directed at surface antigens of neutrophils suffer from _______.
Neutropenia
What is a common treatment for patients that suffer from chronic autoimmunity to blood cells?
Splenectomy (removal of the spleen reduces the rate of blood cell destruction)
What is Goodpasture’s syndrome?
People make antibodies specific for type IV collagen (part of the basement membrane). These antibodies become deposited along the renal glomeruli and renal tubules, eliciting inflammatory responses.
What is the treatment for Goodpasture’s syndrome?
Plasma exchange to remove self-reactive Abs and immunosuppressive drug treatment to prevent production of new Abs
How much kidney failure can be attributed to damage caused by the immune system?
25%
What is Autoimmune (Idiopathic) Thrombocytopenic Purpura?
IgG-mediated inhibition of an enzyme responsible for cleavage of von Wildebrand factor (vWF). vWF normally links platelets and blood vessels with clots
What organs does autoimmune thrombocytopenic purpura effect/what are the symptoms?
Affects kidneys, blood vessels, liver, and brain. Symptoms: thrombocytopenia, bruising, neurological symptoms, microangioplastic hemolytic anemia
Treatment for Autoimmune Thrombocytopenic Purpura
Plasmapheresis (exchange transfusion) with plasma from healthy donors, Rutiximab, RhoGam, steroids
What happens in scleroderma?
Inflammatory destruction of vascular endothelial cells of arterioles and smooth muscle cells, and replacement with collagen and other fibrous materials
Symptoms of scleroderma?
Localized or systemic skin thickening; hard, smooth ivory colored areas of hardened skin
T or F: Rheumatoid factor is required for scleroderma.
F
What tests ID scleroderma?
Presence of ANAs, anti-topoisomerase Abs, and anti-centromere Abs
What is the treatment for scleroderma?
No known cure; patient-specific treatments include drugs that increase blood flow to extremities
What causes acute rheumatic fever?
Antibodies produced during response to bacterial infection cross-react with self-antigens of the human heart
What does acute rheumatic fever have to do with molecular mimicry?
Streptococcal cell-wall components are similar to the constituents of health heart tissue, so antibodies raised as a component of protective response against the bacterium are detrimental to the host
T or F: Acute rheumatic fever can lead to heart valve scarring and myocarditis.
T
What are symptoms of acute rheumatic fever?
Chest pain, fever, weakness, fatigue, and joint pain
T or F: In acute rheumatic fever, B cells can’t be fully activated so no immunological memory results.
T
What are examples of Type II autoimmune diseases?
Autoimmune hemolytic anemia, autoimmune thrombocytopenic purpura, Goodpasture’s syndrome, scleroderma, acute rheumatic fever, pemphigus vulgaris, Grave’s disease, and myasthenia gravis
What is pemphigus vulgarism?
An autoimmune condition mediated by IgG specific for 2 proteins (desmoglein 1 and 3) that results in loss of cohesion in keratinocytes in the epidermis
What are symptoms of pemphigus vulgaris?
Painful chronic blistering of skin
How do you diagnose pemphigus vulgaris?
Punch biopsy of lesion followed by immunofluorescent staining
What is the treatment for pemphigus vulgaris?
Corticosteroids and other anti-inflammatory drugs, rituximab
What are 4 autoimmune diseases of the thyroid gland?
- Hashimoto’s thyroiditis
- Grave’s disease
- Subacute thyroiditis
- Idiopathic hypothyroidism
What are autoimmune diseases of the pancreas?
Type I and Type II diabetes
What is an autoimmune disease of the adrenal gland?
Addison’s disease
What causes Grave’s disease?
Antibodies that bind to the TSH receptor and mimic binding of TSH to the receptor. This results in overproduction of thyroid hormone.
Symptoms of Grave’s disease
Heat intolerance, nervousness, irritability, warm moist skin, weight loss, thyroid enlargement, bulging eye syndrome, characteristic stare
In Grave’s disease, the autoimmune response is biased towards _________.
A TH2 response
What is the treatment for Grave’s disease?
Drug therapy to reduce thyroid function or removal/destruction of the thyroid
T or F: Ab causing Grave’s disease can be transported across the placenta to the developing fetus, so that newborns will suffer from symptoms of the disease.
T
What is myasthenia gravis?
An autoimmune disease in which signaling from nerve to muscle across the neuromuscular junction is impaired
What is the mechanism for myasthenia gravis?
Autoantibodies specific for Ach receptors on muscle cells bind to the receptors, inducing their endocytosis and degradation in the lysosomes. Loss of receptors leaves muscles less sensitive to neuronal stimulation
Treatment for myasthenia gravis
- Immunosuppressive drugs to prevent formation of autoantibodies
- Pyridostigmine to inhibit cholinesterase (which degrades Ach) so that Ach can compete for receptor binding