Immunology Flashcards
Autoimmune pancreatitis - check for?
IgG4 levels
IgG4 disease vs PSC
Both can have cholestatic LFT’s and biliary strictures
IgG4 likely to also have pancreatic involvement
When does T cell development occur in thymus?
In utero - have naive T cells (CD4/CD8) at birth
Process that occurs in thymus cortex?
Positive selection
- Addition of T cell receptor (random through rearrangement
- Ensuring T cell can bind MHC
- Tagging with CD4 or CD8 depending on which MHC it binds
Process in thymus medulla
- Deficiency of AIRE?
Negative selection
- TEst T cells to ensure no autoreactivity and appropriate activity against foreign
- Transcription genese make self antigens
- AIRE makes insulin, cascin - deficiency = autoimmune polyendocrine syndromes
Signal 1
Naive T cell receptor binds antigen/MHC
Binding proteins and STOP signal
Signal 2 -
Costimulation
Initial activation - CD80/86 on APC binding to CD28. Then APC produces CD40 to bind to CD40ligand
Suppression - subsequent production on T cells of CTLA4, PD-1
- CTLA4 binds CD80/86 with higher affinity
CD40ligand deficiency - disease?
Hyper IgM syndrome
No CD40ligand on T cells, so ineffective class swiitching on B cells
FK506?
Tacrolimus
Signal 3
IL-2 binding to CD25 receptor causing T cell
- differentiation (subsets)
- entering cell cycle and proliferation
Role of calcineurin
Dephosphorylates NFAT, which is a transcription factor that stimulates IL-2 production
Blocks release of NFAT, so IL-2 cannot be released
MoA of mTOR inhibitors
Bind FK binding protein
Inhibit IL-2 action including CDK and cyclin production
Induce cell cycle arrest in G1/S
TH1
- target
- cytokines
Intracellular (virus), autoimmunity
TNFa, IFNy, IL-2
TH2
- target
- cytokines
Parasites + allergy
IL-4, IL-5, IL-13
TH17
- target
- cytokines
Extracellular bacteria/fungi. Recruits neutrophils
IL-17A, IL-17F
Treg
- Target
- Cytokines
Suppressess immune system
TGFb, IL-10
How are CD8 cells stimulated to proliferate?
Binding antigen on MHC1
TH1 cells producing IL-2, IL-12 and IFNy to stimulated CD8 proliferation
Mechanism of CD8 cells causing cell death
Stimulate to form perforins, targeted cell killing by inducing apoptosis
Functions of antibodies
Stimulate complement via classical pathway (IgM and IgG)
Recruit immune cells - opsonisation + phagocytosis, antibody dependant cellular cytotoxicity
Neutralise pathogens
Class of antibody determined by?
Heavy chain type
Which antibodies form B cell receptors
IgM
IgD
Chromosome for heavy chain?
Chromosome 14
Antibody diversity
- When does it happen
- How
Occurs in antigen independant in bone marrow
VDJ recombination until functional antibody formed
Allelic exclusion
After VDJ recombination, once functional Ab produced, DNA locked so B cell can ony make one Ab
Immature B cell leaving BM characterised by?
IgM and IgD
Which antibody crosses placenta?
IgG
Which antibodies activate complement
IgM
IgG
Which IgG subclass does not bind complement
IgG4
Function of IgA
Ab found in secretions - first point of defence in areas exposes to outside world
Function of IgE
Embed in mast cells (sensitising event)
Can then be stimulated by re-exposure to antigen to cause mast cel degranulation
B2 cells - antigen dependant class switching process
B cell receptor binds antigen, displays on MHC 2
Co-stimulates CD4 cells, matures an forms subsets
T cell subset produces different cytokines for class switching
- TH1 –> IgG
- TH2 –> IgE and IgA
B2 Somatic hypermutation
B cell receptor binds atigen, DNA uncocked, random mutations to produce higher affinity B cell receptor
Highest affinity receptor selected, proliferates. Becomes:
- Plasma cell
- Memory cell - skips this process next time for faster immune response
B1 cells (t cell independant)
Can bind lipopolysaccharide antigens. Lie in marginal zones of spleen.
Only produce IgM, provide limited immune response to encapsulated organisms
MAC components
C5b - C9
Common complement pathway componentns
All 3 pathways end in C3 convertase
- converts C3 to c3a and c3b
C3b can then also form C5 convertase
- converts C5 to c5a and c5b
General principles of a and b in complement
A - inflammation (anaphylotoxin
B - binds - opsonin or initiates mac
Classical pathway complement
- Recognises?
- Componenets
Immune complexes and damaged cells
C1q, C1r, C1s
C2 and C4 (C2 a and b)
Role of CRP
Activation of complmenet system
Lectin pathway
- good at recognising?
MASPS
Mannin (mannose binding lectin) - found on fungi
Lectin - found on carbohydrate residues, encapsulate bacteria
Regulator of MAC
CD55 and CD59
Disease with lack of CD55 and CD59
- Features
- Rx
PNH
Haemolysis, VTE and organ ischaemia
Eculizumab
Inhibition of factor C3b and C3 convertase
Factor I - C3b
Factor H - C3 convertase
aHUS pathophys and ttraetment
Factor H and I deficiency, dysregulated alternative complement pathway
Rx - Eculizumab
Pathophys and tests for C1 esterase deficienc
Lack of inhibition of bradykinin formation –> angio-oedema
Tests - low C4, low C1 esterase, high C1
Rx - C1 esterase concentrate, bradykinin receptor antagonist
Antibody most potent activator of complement
IgM
IgA forms
Monomer plasma
DImer external body surface
Complmenet responsible for opsonisation/opsonins
C3b
REgulators of alternative pathway
Factor H
Factor I
Properdin
Normal TOtal IG’s
Abnormal vaccination response
Specific antibody deficiency
Most common manifestation of 2nd immunodeficiency cause by chronic systemic steroid use
Bacterial bronchopneumonia
CVID malignancy highest risk
NHL
Recurrent infection with catalse positive bacteria
Staph, Burhilderia, Serratia, fungal
Phagocyte deficiency –> Chronic granulomatous disease
Recurrent infections
Bowel obstructions
Early childhood
Chronic granulomatous disease
Test for CGD
Oxidative burst test - Dihydro rhodamine assay
Recurrent infections
Food allergies
Severe eczema
Hyper IgE syndrome
Hereditary angiooedema cf histamine mediated
- timing
-
Bradykinin - 48-96 hours
No urticaria
Non responsive to antihistamines, steroids, adrenaline
CR3/CR4 deficiency
Leukocyte adhesion deficiency
Umbilical cord takes long time to fall off
CR3/CR4 deficiency
Leukocyte adhesion deficiency
Umbilical cord takes long time to fall off
IL-5
Mepoluzimab
IL-5R
Benralizumab
IL4- Ra
Dupilumab
IgE
Omalizumab
Indications for desensitisation
Antibiotic - done in hospital
Aeroallergin - allergic rhinitis, asthma
Contraindications for desensitisation
Type 3 or 4
SJS/TENS/AGEP
Cause of thunderstorm asthma
Rye grass
Contraindications to skin prick testing for IgE
Recent antihistamine use
Dermatographism or serious skin condition
When to use allergen specific IgE
High risk anaphylaxis
Specific allergen
Recent antihistamines
Type 3 drug reactions
- Cause
- Presentations
Immune complex
Serum sickness
Vasculitis
Lupus Nephritis
Type 2 drug reactions
- Cause
- Presentations
Antibody
Low cell counts due to multiple drugs
- AIHA
- ITP
- Agranulocytosis
Also Anti-GBM
Strongest associated with fatal food anaphylaxis?
Poorly controlled asthma - bronchocosntriction greatest cause of mortality
Atopy vs sensitisation vs allerg
Atopy - genetic tendency to produce specific IgE for allergens
Sensitisation - IgE production following allergen exposure
Allergy - allergen specific IgE and symptoms following exposure
Persistent hypotension on Beta blocker
Give glucagon
Manageement of aspirin induced respiratory disease
Due to COX1 inhibition
Avoid COX1 inhibitors
Intranasal corticosteroids
Oral monteleukast
Synthetic TLR7 agonist
Imiquimod
Most common presentation of IgG deficiency
Normal phenotype
Low C4 - which cryoglobulinaemia?
Type 2 and Type 3
When is varicella infectious
What precautions
1-2 days before rash –> rash cursted over
Droplet
VZV vaccine PPx
- When
- Who to give
Exposure < 5 days
Not immuncompromised, Not pregnant, > 12 months
VZV Ig
- When
- Who to give
Exposure < 10 days
Pregnant or immunocompromised who have inadequate Ig levels (check Ig levels)
Dysregulated response to EBV infection
X linked lymphproliferative disease
Periodic fever syndrome
Inflammasomes
STAT3?
Hyper IgE syndrome
- Prevents Th17 cell production
Common cytokine receptor gamma chain deficiency
SCID
Function of CRP
Bind phospholipi - recognise foreign pathogens and damaged cells
Activates complement system
Benefit of conjugate vaccines
Elicites T cell response (polsaccharide bound to protein), elicits T cell response
Storiform fibrosis
IgG4
Allergy symptoms
Recurrent pancreatitis or sclerosing cholangitis
Good response to steroids
IgG4 disease
Only vaccine CI in egg allergy
Yellow fever
Bone tumour epiphysis
Chondroblastoma
Metaphysis bone cancers
Osteosarcoma
When to stop IVIG in 2nd hypogammagobulinaemia
When Ig levels normalised
MoA of fingolimod
Spingosine 1 phosphate receptor modulator
Prevents leukocyte migration
A/E of fingolimod
Life threateing HSV
Bradycardia
MoA of dupilumab
Indication
Blocks apha subunit of IL-4 (blocks both IL-4 and IL-13)
Eczema
MoA of tofactinib
inhibits JAK1 and JAK3 (in contrast to ruxolitinib)
Indications that can clear allergy status
> 10 years with unknown reaction
Childhood nonspecific exanthem
10 years ago delayed reaction
Delayed anaphylaxis mammalian food
Sensitised event?
Tick bites
Most common cancer immunodeficiencies?
Lymphoma
Management of chemotherapy induced diarrhoea
1st
2nd
1st - loperamide
2nd- SC octreotide
Fluoropyrimidine chemotherapy -severe toxicity with 1st dose
- treatment
- test for?
Uridine triacetate
Check for polymorphisms in F DU metabolising enzymes
Features separating angioodema syndrome vs anaphylaxis
Angiooedema
- No urticaria
- Asymmetrical
- Doesn’t involve dependant areas
Clinical features of HAE
Young
Recurrent abdominal attacks
Diagnostic HAE
Low C4
Normal C1q
C1 inh
-low - HAE 1
- normal but impaired function - HAE 2
Clinical features and associates Acquired angiooedema
Age > 40
Malignancy - NHL
MGUS
Clinical features and associates Acquired angiooedema
Age > 40
Malignancy - NHL
MGUS
Clinical features and associates Acquired angiooedema
Age > 40
Malignancy - NHL
MGUS
Diagnostic acquired angiooedema
Low C4
Low C1 Inh
Low C1q
Super antigen
- Example
- How it works
Exotoxins from staph (TSS)
Can cross link MHC class II antigen presenting cell
AND
The adjacent T cell receptor
Mab with x - composition?
x is cool like a chimera
chimeric
Mab with z - composition?
Humans get z scored
humanised
Mab with m
man = human
fully human
Amplifies normal alternative complement pathway
Foreign or damaged cells
B2 microglobulin - what structure?
MHC1
Where does class switching and somatic hypermutation take place?
Germinal centres - temporary structures formed in 2nd lymphoid organs
What does innate immune system detect?
Pattern recognition
PAMP - microbes only
DAMPS - damage associated peptides
HLH pathophys
Deficient CD8 and NK activity
Unsuppressed macrophage activation