Hunter-Autoimmune Diseases Flashcards
Autoimmune diseases can be related to multiple types of hypersensitivities, but not all. Which ones does it include?
Types 2, 3, 4
NOT Type 1.
In a basic sense, what is an autoimmune disease?
a disease in which your body has a difficult time differentiating self from non-self
Which do we worry more about in terms of developing tolerance to self–B cells or T cells? Why?
We worry MUCH more about T cells than B cells. This is b/c a B cell can almost never mount an attack without T cell help!
Describe what happens to T cells when they are released from the bone marrow?
they go to the thymus
this is where they learn self tolerance
their recognition for things is developed by random combinations–some of these recognize pathogens & some recognize self. They kill the ones that recognize self. Only 3% make it out alive–such carnage!!
What are 2 questions that are addressed when a T cell is maturing in the thymus?
Q1: Do you have an MHCII receptor-like are you basically functional?
Q2: Do you recognize self antigens? If so, you must die.
How do you test these young T cells while they are in the thymus?
you have them come into contact with many MHCIIs that are presenting self antigen. If they react-they die.
The crazy thing is that the self antigens aren’t just thymic–they represent a ton of different things in the body like insulin! The things that aren’t represented aren’t a big deal–they are small in number or secluded in the body away from the immune system.
What is central tolerance in the thymus? What % does this affect?
self-reactive clones undergo apoptosis. 97% of the self-reactive clones die this way.
What happens to the 3% of self reactive clones that aren’t killed via central tolerance?
Peripheral Tolerance!
There are 3 signals required to activate a T cell. The bad guys rarely get that far. They usu die along the way.
What are the signals that are required in the periphery to turn on a T cell?
Have to interact with an APC w/ an MHCII that it recognizes. The APC has to be activated & have B7. CD28 on the T cell must react with that so you get costimulatory signals. Costimulatory also known as CD80/CD86.
If a self-reactive clone escapes central & peripheral tolerance…what is the hope?
regulatory T cells
These will inhibit the T cell/APC interaction & hopefully cause apoptosis.
There is another naturally protective mechanism that the body has to stop the bad T cells. It is the reason that a B cell attack of keratinocytes wouldn’t work.
Keratinocytes do have an MHCII that could react to a bad guy. But they don’t have B7 b/c they aren’t APCs.
A lot of us have T cells that recognize myelin basic protein. Why don’t a lot of us have MS?
b/c it also requires the microglia in our CNS to express B7 from a viral infection or something & to come in contact with the bad T cell. Perfect storm required.
What is a microglia?
It is like the macrophage of the CNS.
What is the perfect storm for autoimmunity?
The ingredients for autoimmunity:
T cells with receptors that see self peptides (not all self reactive T cells are removed by negative selection in the thymus)
Susceptibility genes like MHC that allow certain self peptides to be presented by antigen presenting cells (APC)
A “trigger” that upregulates co-stimulatory molecules on the APC (Infection or tissue damage)
Summary: A self reactive T cell, APC with bad MHC…activate APC to present costimulatory factors.
One of the requirements for a perfect storm is an APC with a bad MHCII for a self antigen. But there is another way for the perfect storm to happen…describe it.
Molecular mimicry.
A self reactive T cell that also recognizes microbial peptides.
APC that presents a microbial peptide that looks like self.
Then the T cell goes on with an attack of self.
What are 2 autoimmune diseases that include genetic susceptibility b/c of MHCI issues–as in a certain HLA?
ankylosing spondilitis
acute anterior uveitis
What are some autoimmune diseases that include genetic susceptibility b/c of MHCII issues–as in a certain HLA?
Goodpasture's MS Grave's Myasthenia Gravis SLE Type I Diabetes Rheumatoid Arthritis Pemphigus Vulgaris Hashimotos
What are some Type II Hypersensitivity Autoimmune diseases that exhibit autoantibodies against surface antigens on blood cells?
autoimmune hemolytic anemia
autoimmune thrombocytopenic purpura
What is the target antigen in autoimmune hemolytic anemia?
erythrocyte membrane antigens–Rh antigens
What is the mechanism of disease in autoimmune hemolytic anemia?
opsonization & phagocytosis of erythrocytes
What are the clinicopathologic manifestations of autoimmune hemolytic anemia?
hemolysis–anemia
What is the target antigen in autoimmune thrombocytopenic purpura?
platelet membrane proteins–integrin
What is the mechanism of disease in autoimmune thrombocytopenic purpura
opsonization & phagocytosis of platelets
What are the clinicopathologic manifestations of autoimmune thrombocytopenic purpura?
bleeding
What are some Type II Hypersensitivity Autoimmune diseases that exhibit autoantibodies against cell surface antigens or fixed tissues?
pemphigus vulgaris
goodpasture’s
acute rheumatic fever
What is the target antigen with pemphigus vulgaris?
proteins in intercellular junctions of epidermal cells (epidermal cadherin)
What is the mechanism of disease in pemphigus vulgaris?
antibody-mediated activation of proteases
disruption of intercellular adhesions
What are the clinicopathologic manifestations of pemphigus vulgaris?
skin vesicles (bullae)–it is a skin disease
What is the target antigen of good pasture’s?
noncollagenous proteins of the basement membrane of kidney glomeruli & lung alveoli
What is the mechanism of disease in good pasture’s?
complement & Fc-receptor mediated inflammation
What are the clinicopathologic manifestations of autoimmune good pasture’s?
nephritis, lung hemorrhages
What is the target antigen of acute rheumatic fever?
streptococcal cell wall antigen-antibody cross reacts with myocardial antigen
What is the mechanism of disease in acute rheumatic fever?
inflammation
macrophage activation
What are the clinicopathologic manifestations of acute rheumatic fever?
myocarditis & arthritis
What are some Type II hypersensitivity autoimmune diseases that exhibit autoantibodies against cellular receptors?
Grave’s Disease
Myasthenia Gravis
What is the target antigen for Grave’s Disease?
TSH receptor
What is the mechanism of disease in Grave’s Disease?
antibody-mediated stimulation of TSH receptors
What are the clinicopathologic manifestations of Grave’s Disease?
hyperthyroidism
What is the target antigen for Myasthenia Gravis?
Ach receptor
What is the mechanism of disease for myasthenia gravis?
antibody inhibits Ach binding, down regulates receptors
What are the clinicopathologic manifestations of myasthenia gravis?
muscle weakness, paralysis
The mechanism of autoimmune hemolytic anemia is similar to what other disease? What are the basics of it?
similar to extrinsic hemolytic anemia (including drug-induced)
**T cells & B cells recognize antigens on the surface of the RBC. Causes lysis or phagocytosis
A 29-year-old man presented with spontaneous bruising of his arms and chest. He had three recent epistaxes but no other bleeding. He was not taking any drugs and had no risk factors for HIV. The spleen was not palpable. On investigation, he had a normal hemoglobin (138 g/l) and white cell count, but a low platelet count of 10 × 106/ml (normal >150 × 106/ml). His serum CRP and immunoglobulin levels were normal; direct Coombs’ test was negative; antinuclear and DNA-binding antibodies and rheumatoid factor were absent. His bone marrow contained an increased number of normal megakaryocytes but was otherwise normal.
What does this patient have? What is the proper treatment for him?
A diagnosis of immune thrombocytopenia was made and he was started on a high dose of prednisolone. His platelet count rose rapidly over the next few days and the steroids were tailed off over 4 weeks. He relapsed 10 months later with further bruising, but again responded to a short course of oral steroids.
What happens in autoimmune thrombocytopenia?
autoantibodies formed against goiib: iii a–a platelet plasma membrane integrin
**these antibody coated platelets are destroyed by phagocytes in the liver & spleen
What is usu the proper treatment for autoimmune thrombocytopenia?
corticosteroids–to inhibit phagocytosis
splenectomy