Autoimmune Diseases Flashcards
What are the two factors that combined together lead to autoimmune disease?
inheritance of susceptibility genes and exposure to environmental triggers
What groups of genes contribute the most to autoimmune disorders?
HLA genes
How can infections lead to autoimmunity? 4 ways…
- up-regulate the expression of co-stimulators on APCs meaning APCs that carry self antigens might still activate T cells that will them be reactive against self
- Molecular mimicry - where antigens from the infection look like self antigen enough to have cross-reactivity
- Some viruses can cause polyclonal B-cell activation, which may result in production of autoantibodies
- infection leads to tissue injury which may release self antigens and structurally alter self antigen sot hey are able to activate T lymphocytes
Describe the typical clinical course of untreated autoimmune disease.
They tend to be progressive: there may be sporadic relapses and remissions, but overall ther is inexorable tissue damage if untreated
Why are systemic autoimmune diseases often reffered to as collagen vascular diseases?
they tend to involve blood vessels and connective tissue
What’s the udnerlying pathologic mechanism of systemic lupus erythematosis?
it’s a multisystem autoimmune disorder characterized by the formation of multiple autoantibodies, particularly antinuclear antibodies that results in widespread multi-organ tissue damage
What organ systems are most often affected by SLE?
skin, joints, kidney, serosal membranes
Why do people with lupus often have cytopenias?
because they often have antibodies directed against red cells, platelets and lymphocytes
Why do patients with SLE often have false positive syphilis tests and false prolongation of the PTT?
Because they often make anti-phospholipid antibodies that interfere with the reagents in these tests
Because of the anti-phopholipid antibodies, patients with SLE often have secondary anti=phospholipid antibody syndrome, which is associated with what?
venous and arterial thrombosis
spontaneous miscarriages
cerebral ischemia
What are some of the environmental triggers we think play a role in the onset of SLE?
infections, UV light, estrogen, extreme stress
What sort of hypersensitivity reaction leads to the majority of the tissue injury in SLE?
type 3 - the deposition of antigen-antibody complexes
What are the clinical signs/criteria for SLE? (SOAP BRAIN MD)
Serosis Oral ulcers arthritis photosensitivity blood (hematologic disorders - cytopenias) renal disorder antinuclear antibody immunological disorders (other autoantibodies) neurologic disorders malar rash discoid rash
Why can SLE involve multiple organ systems?
Because it causes acute necrotizing vasculitis, which can happen anywhere - in any organ
Why do you get kidney issues in lupus?
you get immune complex deposition in the glomeruli
How does the joint involvement in lupus differ from that in RA?
it’s non-erosive and non-deforming, involving small joints
What are the effects of lupus on the lungs?
pleuritis, pleural effusions, interstitial fibrosis
What’s the most ocmmon cause of death in patients with lupus?
infection due to immunosuppression
What is the best screening test for SLE?
start with an ANA
then follow-up a positive ANA with anti-dsDNA and anti-smith antibodies
What’s the underlying pathologic mechnanism of RA?
- exposure to an arthritogenic antigen in predisposed individuals
- initial acute arthritis leads to a continuing autoimmune reaction with activation of CD4+ help T cells and the release of inflammatory mediators and cytokines
- you get a nonsuppurative proliferative and inflammatory synovitis that progression to destruciton of the articular cartilage and ankylosis of the joints
What two alleles are especially associated with risk for RA?
HLA-DRB1 and PTPN22
What type of protein formed in the body (especially in smokers) has been implicated as a potential autoantigen in RA?
citrullinated proteins
proteins modified by enzymatic conversion of arginine to citrulline
What’s the term for the mass of inflamed synovium that grows over joint cartilage in affected joints for RA?
pannus
Besides the anti-cyclic cirtullinated peptide antibodies, what antibody is seen in RA? Is it more or less specific than the AACP?
rheumatoid factor (IgM autoantibodies to Fc portion of IgG) It's less specific because it can be seen in 5% of healthy individuals
What is the underlying pathogenesis of Sjogren syndrome?
Pathogenesis is thought to be related to aberrant T and B cell activation - you get lymphocytic inflammation and fibrosis of lacrimal and slaivary glands and potentially parotid gland enlargement
What are the typical pathologic and clinical findings of sjogren’s syndrome/
- dry eyes (keratoconjuncitivtis sicca)
2. dry mouth (xerostomia)
What are the antibodies against in sjogren’s syndrome?
SS-A and SS-B, but it’s not specific
What type of neoplasm can be seen in sjogren syndrome?
increased risk for lymphoma (marginal zone lymphoma in aprticular)
What’s the underlying pathogenesis of scleroderma (systemic sclerosis)?
cause unknown, but they think it’s an abnormal immune response by CD4+ T cells to unknown antigens, with release of cytokines that activate inflammatory cells and fibroblasts
You get ischemic damage and fibrosis in affected organs