L14 - Autoimmunity 2 COPY Flashcards
MOLECULAR MIMICKRY
i) what is it? what does it lead to?
ii) which MHC are viral peptides presented on? which T cell recognises this? what does this cause in the T cell?
iii) what do the viral peptides resmble in MM? what does this cause the T cell do do?
iv) what does the MM process depend on? (2)
i) epitopes relevant to the pathogen are shared with host antigens leading to an immune response in the host due to cross reactivity
ii) viral peptides presented on MHC II and recognised by CD4 T cells > activates the T cell
iii) viral peptides resemble host derived peptide > causes the T cell to now strongly react to self peptide and initiate inflammation
iv) process dep on having correct MHC to present the epitope common to the host and virus (inherited) and also having the correct T cell to recognise it (bad luck)
EXAMPLES OF MOLECULAR MIMICRY
i) what can occur after mycoplasma pneumoniae? what is the myocoplasma antigen homologous to in the host?
ii) which Ig is released to mycoplasma and can also cause response to host tissue? how long does this last?
iii) what can occur after streptococcal infection? name three areas it can affect
iv) what do anti strep antibodies cross react with?
i) autoimmune haemolysis can occur post mycoplas pneumoniae as mycoplas antigen has homology to I antigen on RBCs
ii) IgM to mycoplas can cause hameolysis = transient response and settles when infection is cleared
iii) rheumatic fever post strep infection
- affects heart, joints, skin, brain
iv) anti strep ABs cross react with connective tissue
T1DM - IMMUNOLOGY
i) which cells undergo autoimmune destruction? what does this lead to a lack of? name three symptoms seen
ii) when is antibody detectable in relation to onset of clinical disease? what does this mean we can do?
iii) what does an early pancreatic biopsy show? is there active inflammation when the patient presents? why?
iv) are autoantibodies thought to be responsible for destruction of pancreas?
i) beta cells in islets of pancreas > lack of insulin
- polyuria, polydipsia, polyphagia, weight loss
ii) islet cell antibody is detectable for months to years before the onset of clinical disease > track blood of those at risk
iii) early panc biopsy shows CD4/CD8 T cell infiltration
- there is not active inflam when the patient presents as it has already been destroyed
iv) no
PROGRESSION TO T1DM
i) what molecules confer genetic suceptibility?
ii) what can trigger progression to autoimmune disease?
iii) what event happens before clinical onset? what cells are seen in the pancreas?
iv) which protein is lost after clinical onset? what % of the pancreas has been destroyed when overt diabetes has developed?
v) label diagram
i) HLA molecules
ii) enviro trigger can cause progress to AI disease
iii) autoantibod insulinitis pre clinical onset
- see T cell infiltrating the pancreas
iv) loss of C peptide after clinical onset
- 90% of panc destroyed at this point
v) A - genetic suscep, B - enviro trigger, C - auto antibod infiltrate panc, D - clinical onset, E - loss of C peptide
GENETICS AND TYPE 1 DIABETES
i) what is the approx concordance in monozygotic twins? what does this show?
ii) what type of HLA alleles are the major defined risk factor? having one of which two alleles give relative risk of 6? what is the relative risk of having both?
iii) what are the HLA molecules thought to be responsible for? what other disease is this seen in?
iv) which two things may be required for an AI response?
i) almost 100% concordance > genetic background is important
ii) HLA class II alleles most important
- DR3 or DR4 = RR 6
- DR3 and DR4 = RR 15
iii) HLA molecules thought to be responsible for presenting relevant islet cell antigens to CD4 T cells (also seen in coeliac)
iv) need appropriate T cell receptors and other genetic/enviro cofactors
PRECIPITATING EVENTS FOR T1DM
i) how long before diagnosis can autoantibodies to islet cells be detected? why is it difficult to identify triggers?
ii) what can viral infection with coxsackie virus cause in mice and humans? what does this precipitate to in mice?
iii) which protein does protein 2C from the coxsackie virus have homology with? what mechanism may be mediating the reaction
i) autoantibods present months-years before clinical onset
- hard to identify triggers as there is a gap between init of disease and presentation
ii) coxsackie virus infection can cause pancreatitis > ppt to autoimmune diabetes in mouse models
iii) protein 2c from coxsackie has homology with islet cell antigen glutamuc acid decarbox (GAD)
- may be through molecular mimicry mech
MULTI STEP DEVELOPMENT OF AI DISEASE
i) what is critical for determining which peptides can be presented? what arm of the immune system is AI disease always about?
ii) which part of the T cell repertoire is inherited? which part involves random recombination
iii) what may influence T ad B cells to be autoreactive?
i) MHC background > AI always involves adaptive immunity
ii) gene segments for the TCR are inherited by production of the receptors is done by random recomb so will differ even between identical twins
iii) infection can cause T and B cells to be autoreactive
SYSTEMIC LUPUS ERYTHEMATOSIS
i) what type of AI disorder is it?
ii) what type of rash is commonly seen in skin? what two other things can be seen in skin? how are the kidneys/lungs/joints affected
iii) what group of people is it most common in (sex and age) which ethnic group?
iv) what is it associated witht the presence of? what do these do?
v) give two other things that can precipitate the disease?
vi) which proteins may some patients be deficient in?
i) multi system AI disease
ii) see butterfly lupine rash + photosensitivity and hives
- nephritis, pulm fibrosis, joint pain
iii) most common in women of reproductive age and asian/african descent
iv) associated with presence of anti nuclear antibodies
- collection of antibodies that react with cell nuclei/cell div apparatus
v) immune complex deposition and disordered apoptosis can also ppt disease
vi) some patients may deficient in classical complement components eg c1,c4,c2
CLASSICAL COMPLEMENT DEFICIENCY
i) name three complement proteins that can be implicated in lupus?
ii) what do these proteins usually do? what happens when they are absent?
i) C1q, C2 and C4 > deficiency can predis to lupus
ii) these prots usually enhance phagocytosis of immune complexes > deficiency may mean that immune complexes arent removed by spleen
AUTOIMMUNE SEROLOGY FOR DIAGNOSIS
i) give three roles of autoantibodies in immune disease
ii) what are the three methods for detection? which two detect AB in the blood? which one detects AB bound to tissue in a biopsy?
i) Abs can have diagnostic value, be pathogenic or just have a bystander effect
ii) detect by indirect immunofluoresc/solid phase immunoassay (det AB in blood) or direct immunofluro (biopsy)
INDIRECT IMMUNOFLUORESENCE
i) where are antibodies detected from?
ii) what is the glass slide covered with? what is added to the well?
iii) what secondary antibody is added? why?
iv) how is the test read
i) ABs detected in the blood
ii) glass slide covered with tissue of interest from animal etc
- add patient serum to the well (if antibodies are pres they will bind)
iii) detection antibod labelled with a fluorescent marker
iv) looking for fluoresence under microscope using UV light
T1DM AND INDIRECT IMMUNOFLUORESCENCE
i) give three reasons why its important to detect T1DM
ii) which tissue is used to coat the wells? what does positive staining indicate?
iii) is this technique the best way to detect T1DM? what is better?
iv) are the antibodies in T1DM pathogenic?
i) risk of ketoacidosis, requires insulin and monogenic/T2DM req a different approach
ii) coat wells with monkey pancreas > positive staining indicates presence of islet cell autoantibodies
iii) this method is now being replace with immunoassays for specific antigens eg GAD
iv) antibods are not pathogenic
IMMUNOASSAY TO DETECT ANTIBODIES
i) where are antibodies detected? name a technique used
ii) what is the well coated in? what is added to the well?
iii) why are enzyme linked antibodies then added? what is added after this?
iv) how is the amount of antibody present quantified?
v) name a technique this is now being replaced with
i) in the blood - ELISA
ii) well is coated in pure source of relevant antigen
- add patient serum that may/may not contain antibodies
iii) enzyme linked antibody then added to bind the specific antiody in the patient serum
- then add a substrate and the enzyme converts this to a coloured product
iv) amount of specific antibody is proportional to the rate of colour formation
v) being replaced with newer more automated methods eg particle bead suspension
ELISA ASSAY
i) what are wells coated with and what is added to wells?
ii) what type of Ig is the secondary antbody that is added? what does this bind to? what is it cov linked to?
iii) what is needed to make the experiment valid?
iv) what is produced from the readings from each well?
i) coat wells with antigen of interest and add patient serum
ii) secondary antibody is IgA which binds to IgA Fc regions
- cov linked to an enzyme eg horseradish peroxidase > colour change when substrate is added
iii) need wells with known concentrations of antibody - pos and neg controls
iv) produce a standard curve from readings
DIRECT IMMUNOFLUORESENCE
i) where does it detect antibodies?
ii) what is put on the slide? in what situation will antibody already be present?
iii) what is added next? how is the result visualised?
i) in tissue biopsy
ii) put the tissue on a slide
- if damage is mediated by an antibody then antibody will already be stuck to the antigen in the tissue
iii) then added detection antibody with fluoresecent marker and look under MS
