Autoimmunity (Introduction, Systemic Autoimmune Disease) Flashcards
introduced “horror autotoxicus” or
“fear of self-poisoning” in 1900s
Paul Ehrlich
Immune responses are targeted toward self-antigens resulting to organ and tissue damage
Autoimmune diseases
Autoimmune diseases can be caused by
T-cell–mediated immune responses
Autoantibodies directed against host antigens
ETIOLOGY of autoimmunity
Self-Tolerance
Genetics
Other endogenous & environmental factors
ability of the immune system to accept self-antigens and not initiate a response against them
Self-Tolerance
a state of immune unresponsiveness that is directed against a specific antigen, in this case, a self-antigen
Immunologic Tolerance
2 levels of Immune Tolerance
Central Tolerance
Peripheral Tolerance
immune tolerance that occurs in central or primary lymphoid organs (thymus & BM)
Central Tolerance
involves negative and positive selection during T cell maturation
Central Tolerance
involves receptor editing in B cells
Central Tolerance
result from anergy caused by absence of costimulatory signal from an antigen-presenting cell (APC) or binding of inhibitory receptors such as CTLA-4
Peripheral Tolerance
specific state of unresponsiveness to the antigens
anergy
molecule that prevents T-cell activation
CTLA-4
in terms of genetics, autoimmunity is prevalent in these groups
family members and among monozygotic (genetically identical) twins
than dizygotic (non-identical) twins or siblings
Other Endogenous and Environmental Factors
Hormonal Influence
Tissue Trauma and Release of Cryptic Antigens
Microbial Infections
women are ___ more likely to acquire an
autoimmune disease than men
2.7x
___ of pt. with autoimmune dse are females
78%
female hormones that may place women at a greater risk for developing autoimmune dse
estrogen, androgen, prolactin
“immunologic tolerance” some self-antigens
may be cryptic, or hidden within host’s tissue
Tissue Trauma and Release of Cryptic Antigens
tissue damage could be caused by factors:
▪ infections
▪ contact with environmental toxins
▪ physical injury from UV radiation exposure
Mechanisms of Microbes in triggering autoimmune response
1) Molecular mimicry
2) Bystander effect
3) Superantigens
4) Epigenetics and Modification of Self-Antigens
5) Interactions Between Factors
many bacterial or viral agents contain antigens that closely resemble the structure or amino acid
sequence of self-antigens
Molecular mimicry
example of molecular mimicry
gram-positive bacterium S. pyogenes and
rheumatic fever (scarlet fever/pharyngitis)
production of antibodies to the M protein and N-acetyl glucosamine components of the bacteria, which crossreact with cardiac myosin, causing damage to the heart
Molecular mimicry in scarlet fever or pharyngitis
microorganism can induce a local inflammatory
response that recruits leukocytes and stimulates
APCs to release cytokines that nonspecifically
activate T cells
Bystander effect
proteins produced by various microbes that bind to both class II MHC molecules and TCRs, regardless of their antigen specificity
Superantigens
example of superantigen
staphylococcal enterotoxins
Epstein-Barr virus (EBV) and cytomegalovirus (CMV)
can cause polyclonal activation of B cells
Epstein-Barr virus (EBV) and cytomegalovirus (CMV)
superantigens produced can act as potent T-cell mitogens by activating a large number of T cells with different antigen specificities
staphylococcal enterotoxins
modifications in gene expression that are not caused by changes in original DNA sequence
Epigenetics
citrullination of collagen leads to
RA
glycosylation of myelin leads to
Multiple Sclerosis
complex interactions between genetic and environmental factors may cause break in
immunologic tolerance, autoreactive T cells recognize and proliferate in response to self-antigens and B cells develop into plasma cells that secrete autoantibodies
Interactions Between Factors
a chronic systemic inflammatory disease
SLE
peak age of onset of SLE
20-40 yo
W:M of SLE
9:1
5 yr survival rate of SLE
90%
etiology of SLE
complex interactions between environmental factors, genetic susceptibility, and abnormalities within immune system
genetic defects in genes coding for these increases the chance of developing lupus
HLA-A1, B8, DR3
result in uncontrolled autoreactivity of T and B cells, which leads to production of numerous autoantibodies in SLE
polymorphisms in genes
genes coding for various cytokines
genes involved in signaling of innate immune response
What will be the result if there is a hidden or cryptic self antigens?
T and B lymphocytes are shielded and not educated to become tolerant. (No recognition since hidden)
changes at protein level during epigenetics and modification of self-antigens
post translational modification
biochemical processes:
acetylation
lipidation
citrullination
glycosylation
Associated autoantibodies in SLE
Ab to dsDNA, histones, and other nuclear components
Autoantibody to lymphocytes
Autoantibody to erythrocytes
Autoantibody to platelets
Autoantibody to ribosomal components
Autoantibody to endothelium
Phospholipid Ab
RF
present in 70% of patients with lupus
Antibodies to dsDNA (AntidsDNA)
Ab highly specific for SLE
Antibodies to dsDNA (AntidsDNA)
found in immune complexes that are deposited in
organs such as kidneys and skin of patient with SLE
AntidsDNA
complement protein
most pathogenic, forms intermediate size complexes that become deposited in glomerular basement membrane (GBM)
Accumulation of IgG to dsDNA
activate complement and initiate an inflammatory response
Immune complexes
attracted to sites of inflammation and release cytokines that perpetuate the response, resulting in tissue damage
Leukocytes
Antibodies to RBCs indicates
hemolytic anemia
Antibodies to platelets indicates
thrombocytopenia
Antibodies to endothelial cells indicates
inflammation of blood vessels and vascular damage in lupus, vasculitis and neuropsychiatric symptoms
Phospholipid antibodies indicates
increased miscarriage, stillbirth, and preterm delivery in pregnant women with lupus
occurs in up to 8% of babies born to pregnant women with SLE, associated with antibodies to the nuclear antigens, SS-A/Ro and SS-B/La
Neonatal lupus
nuclear antigens where neonatal lupus antibodies are associated
SS-B/La
SS-A/Ro
serious complication that occurs in 2% of fetuses whose mothers have anti–SS-A antibodies
In utero heart block
clinical symptom in 90% of patients with SLE
polyarthralgias or arthritis
symmetric and involves small joints of the hands,
wrists, and knees
arthritis
may appear on any area of the body exposed to UV light in 80% of SLE patients
erythematous rash or butterfly rash
found in 50% of SLE patients
renal involvement leading to renal failure
end stage renal dse, deposition of immune complexes in subendothelial tissue and thickening of basement membrane
nephritis, diffuse proliferative glomerulonephritis
symptoms usually disappear once the drug is discontinued; milder form of the disease; manifested as fever, arthritis, or rashes; kidneys are rarely involved
drug-induced SLE
Systemic Lupus International Collaborating Clinics criteria (2012)
Clinical criteria
Immunologic criteria
give examples of clinical criteria and immunologic criteria
Clinical criteria
▪ acute cutaneous lupus
▪ chronic cutaneous lupus
▪ oral ulcers
▪ non-scarring alopecia (hair thinning/fragility)
▪ synovitis
▪ serositis
▪ renal involvement
▪ neurological symptoms
▪ hemolytic anemia
▪ leukopenia
▪ thrombocytopenia
Immunologic criteria
▪ elevated antinuclear antibody titer
▪ elevated anti-dsDNA titer
▪ presence of antibody to the Sm nuclear antigen
▪ presence of antiphospholipid antibody
▪ low complement levels
▪ + direct Coombs’ test in hemolytic anemia absence
what is needed to be classified as having SLE
4 of the 17 criteria, including at least 1 clinical criterion and 1 immunologic criterion
treatment for SLE with mild symptoms
high dose of aspirin (brings relief)
treatment for skin manifestations of SLE? what is the action?
Antimalarials (hydroxychloroquine/chloroquine and topical steroids)
Antimalarial drugs – inhibit signaling of TLR 7, 8, and 9
treatment for acute fulminant (severe & sudden) lupus, lupus nephritis, or CNS complications because these suppress immune response and lower antibody titers
Systemic corticosteroids