Immune Flashcards
Why does SCID only present at 3 months of age?
- Why 3 months? Because prior to 3 months, there is active transport of maternal IgG across placental to help protect baby
Describe ADA def SCID. What will the T, B and NK cells be?
ADA deficiency
- 16.5% of all SCID
- Autosomal recessive
- Adenosine deaminase (ADA)
- Enzyme required for cell metabolism in lymphocytes
- Lack of this enzyme → accumulation of toxic productions e.g adenosine, 2deoxyaenosine, deoxyadenosine-triphosphate which kills lymphocyte
- Phenotype
- Low/absent T
- Low/absent B
- Low/absent NK
What is the most common form of SCID? Describe the molecular protein and clinical picture.
X-linked SCID
- Most common form of SCID
- 45% of SCID
- Mutation in gamma chain of IL2 receptor on chromosome Xq13.1
- This is shared between receptors for IL2, IL4, IL7, IL9, IL15 and IL21
- Inability to respond to cytokines, causing early arrest of T cell and NK cell development, production of immature B cells
- Phenotype
- Low/absent T
- Low/absent NK
- Normal or increased B but low Igs (because immature)
Clinical phenotype of SCID
- Infection of all types
- Candidate and diarrhoea common early features
- Bacterial, viral, fungal, protozoal
- Failure to thrive
- Unusual skin disease
- Colonisation of infant’s empty bone marrow by maternal lymphocytes
- Graft v host disease
- FH of early infant death
- Clinical features
- High forehead
- Low set, abnormally folded ears
- Cleft palate, small mouth and jaw
- Hypocalcaemia
- Oesophageal atresia
- Underdeveloped thymus
- Complex congenital heart disease
DiGeroge Syndrome
- Deletion of 22q11.2 → developmental defeat of pharyngeal pouch (blue box)
- Underdeveloped thymus → reduced T cells but normal B cells
- Immune function is usually only mildly impaired and improves with age
Common clinical picture of a T cell def (primary or secondary)
- Viral infections (CMV)
- Some bacterial infections (esp intracellular pathogens)
- Mycobacteria TB, Salmonella, Listeria
- Parasite infections
- Toxoplasma
- Fungal infection
- Pneumocystitis jiroveci (also associated with hyperIgM even though this is a B cell problem because of abnormal T cell function present in this condition)
- Early malignancy
- CD4 deficiency will impact development of T cell dependent antibody response
Common clinical picture of a B cell def (primary or secondary)
- Lack of antibodies!
- Bacterial infections
- Eep encapsulated bacteria (H.influexa, Strep pneu, Strep pyrogens, Pseudomonas)
- Some viral - enterovirus
- Toxins
- Tetanus, diphtheria
Skin barrier against infection (4)
- Tightly packed keratinised cells
- Limits colonisation by microbes
- Physiological factors
- Low pH
- Low oxygen tension
- Sebaceous glands
- Hydrophobic oils repel water and microbe
- Lysozyme destroys structural integrity of bacterial cell wall
- Ammonia and defensives have anti-bacterial properties
- Commensal bacteria
- Compete of pathogenic microbes for scarce resources
- Produce fatty acids and batericidins that inhibit growth of pathogen
Mucosal barriers against infection (2)
- Secretes mucus
- Physical barrier to trap invading pathogens
- Secretory IgA prevents bacteria and viruses attaching to and penetrating epithelial cells
- Lysozyme and antimicrobial peptides directly kill invading pathogen
- Lactoferrin acts to starve invading bacteria of iron
- Cilia
- Trap pathogens and contribute to removal of mucus
- Assisted by physical manoeuvres such as sneezing and coughing
Cells of the innate immune system (7 types and 4 classes)
- Polymorphs - neutrophils, eosinophils, basophils
- Monocytes and macrophages
- NK cells
- Dendritic cells
Soluble components of innate immune system (3-4 types)
- Complement
- Acute phase protein e.g. CRP
- Cytokines and chemokines
- Cytokines increase vascular permeability
- Chemokine’s attract neutrophils
Receptors expressed on polymorphs - neutrophils, eosinophils and basophils (4)
- Expresses cytokines and chemokine receptors - detect inflammation
- Expresses pattern recognition receptors - detect pathogens
- Express Fc receptors for Ig - detect immune complexes
Function of polymorphs (innate immunity)
- Capable of phagocytosis/oxidative and non-oxidative killing - particularly neutrophils
- Release enzymes, histamine, lipid mediators of inflammation from granules
- Secrete cytokine and chemokine to regulate inflammation
Describe oxidative killing in macrophages and neutrophils
- NAPDH oxidase complex convert oxygen to ROS - superoxide and H2O2
- Myeloperoxidase catalyses production of hydrochlorous acid from H2O2 and chloride
- Hydrochlorous acid is a very effective oxidant and anti-microbial
Describe non-oxidative killing by phagocytes e..g neutrophils and macrophages
- Release of bactericidal enzymes e.g lysozyme and lactoferrin (depletes pathogen of iron) into phagolysosome
- Enzymes are present in granules
- Each has unique antimicrobial spectrum
- Results in broad coverage against bacteria and fungi
How does phagocytes recognise a pathogen?
- Recognition of pathogen by pattern recognition receptors
- Toll-like receptors and mannose receptors
- Generic pathogen-associated molecular patterns (PAMPS) such as bacterial sugar, DNA, RNA
- Fc receptors for Fc portion of Ig to allow recognition of immune complexes
NK cell function (2)
- When inhibitory signals are lost (altered) e.g when cells are infected or becomes malignant. NK cells become activated and kills those altered cells
- Secrete cytokines to regulate inflammation - promote dendritic cell function
Background:
- Present within the blood and can migrate to inflamed tissue
- Innate immunity but a lymphocyte
- Inhibitory receptors for self-HLA and prevent inappropriate activation by normal self
- Activator receptors including natural cytotoxicity receptors that recognise heparin sulphate proteoglycans
- But generally inhibitory signal > activator signals
Functions of T helper (CD4) cells (2)
- Immunoregulatory functions via cell-cell interactions and expression of cytokines
- Development of full B lymphocytes and some CD8+ lymphocyte response
Functions of CD8 T cells
- Specialised cytotoxic cells which kill cells directly (perforin, granzyme, Fas/FasL pathway)
- Secrete cytokines e.g. IFN-y, TNF-a
- Particularly impt. in the defence against viruses and tumours
What is immunological memory
Response to successive exposures is qualitatively and quantitatively different
- pool of memory T/B cells that are more easily activated (T and B)
- Secretes more antibodies (B) that are of higher specificity IgG instead of IgM
- B memory cells do not require CD4+ help
Express receptors that recognise peptides usually derived from intracellular proteins and expressed on HLA Class 1
CD8 T cells
Subset of lymphocytes that express Foxp3 and CD25
T reg
Subbed of cells that express CD4 and secret IFNa and IL2
Th1
Play an important role in promoting germinal centre reactions and differentiation of B cells in to IgG and IgA secreting plasma cells
T follicular helper cells
Describe central tolerance of B cells
Any premature B cell that recognises self is killed to avoid auto reactivity (not concept of intermediate binding etc as in T cell because they do not need to recognise HLA/own antigens)
What is the germinal centre reaction in lymph nodes wrt to T and B cells (3)
- APC prime CD4+ cells
- CD4+ t cells help B cell differentiate via CD40L:CD40
- B cell proliferation with somatic hypermutation and isotope switching
Result: IgE, IgG and IgA from B cell
Structure of an antibody (light or heavy chain)
- Fab?
- Fc?
- Two heavy and two light chain
- Heavy change determine the class (IgM, IgG, IgA, IgE and IgD)
- Antigen recognised by Fab (light and heavy chain)
- Effector function is Fc (only heavy chain)
Describe the classical compliment pathway
Antibody-Antigen complexes, results in change in antibody shape to expose binding site of C1, depends on adaptive immunity (late)
Describe the MBL pathway
Mannose binding lectin: Activated by binding of MBL to microbial cell surface carbohydrates, directly stimulates the classical pathway involving C2 and C4 (but not C1), do not require adaptive immunity
Describe the alternative complement pathway
- Alternative: Directly triggered by binding of C3 to bacterial cell wall component e.g. LPS and teichoic acid of Gram+, do not require adaptive immunity
Functions of complement (5)
- Increase vascular permeability and cell trafficking to site of inflammation
- Opsonisation of immune complexes to keep them soluble - hence def in complements in SLE leads to autoimmunity as self antigens now persist and becomes ‘visible’
- Opsonisation of pathogen to promote phagocytosis
- Activates phagocytes
- Promote mast cell/basophil degranulation
What are cytokines and chemokine
Cytokines are small protein messengers with immunomodulatory function
Chemokines are subset of cytokines with chemoattractant properties
Interaction of X and X with X is important for dendritic cell trafficking to lymph nodes
Interaction of CCL19 and CCL21 with CCR7 is important for dendritic cell trafficking to lymph nodes
CCL19 and CCL21 are ligands for CCR7 (receptor)
Recurrent infections with high neutrophil counts on FBC but no abscess formation
leukocyte adhesion deficiency
Recurrent infections with hepatosplenomegaly and abnormal DHT
Chronic granulomatous disease
Recurrent infections with no neutrophils on FBC
Kostmann syndrome
infection with atypical mycobacterium. Normal FBC
IFN gamma receptor deficiency
Meningococcus meningitis with FH of sibling dissing of same condition aged 6
C7 deficiency
Membranoproliferative nephritis and bacterial infections, abnormal fat distribution
C3 deficiency with presence of a nephritic factor
Severe childhood onset SLE with normal levels of C3 and C4
C1q deficiency
Recurrent infections with receiving chemotherapy but previously well
MBL deficiency
Failure to produce ALL myeloid or lymphoid cells (ultimate failure)
- diagnosis
- inheritance pattern
- enzyme mutation
- treatment
- Reticular dysgenesis - autosomal recessive severe SCID
- Mutation in mitochondrial energy metabolism enzyme adenylate kinase 2 (AK2)
- Fatal early unless treated wth BM transplant
- Failure to produce neutrophils (more specific failure) - 2 types
- diagnosis
- inheritance pattern
- enzyme mutation
- Specific failure of neutrophil maturation in bone marrow (failure of differentiation)
- Kostmann syndrome - autosomal recessive severe congenital neutropenia
- Classical form due to mutation in HCLS1-associated protein X1 (HAX1)
- Cyclic neutropenia - autosomal dominant episodic neutropenia every 4-6 weeks
- Mutation in neutrophil elastase (ELA-2)
Kostmann syndrome - mutated enzyme
HCLS-1 associated protein X1 (HAX1)
Cyclic neutropenia - mutated enzyme
Mutation in neutrophil elastase (ELA-2)
- Cyclic neutropenia - autosomal dominant episodic neutropenia every 4-6 weeks
- Mutation in neutrophil elastase (ELA-2)
- Defect of phagocyte migration
Leukocyte adhesion deficiency (Deficiency of CD18 - beta2 integrin subunit)
pathophy of leuckotee adhesion deficiency
- Leukocyte adhesion deficiency (Deficiency of CD18 - beta2 integrin subunit)
- CD18 combines with CD11 to form LFA-1 which is expressed on neutrophils
- LFA-1 binds to ICAM-1 on endothelial cells to allow neutrophils to adhere and transmigrate
- When CD18 is absent, neutrophils cannot interact with adhesion molecules and fail to exit from blood stream
- You get high neutrophil counts in blood but absence of pus formation
Failure of oxidative killing mechanism
Chronic granulomatous disease
Pathophy of CGD (chronic granulomatous disease)
- Chronic granulomatous disease
- Absent respiratory burst
- Deficiency in NADPH oxidase
- Inability to generate ROS required for killing
- Excessive inflammation but cannot kill
- Then form granulomas instead (because neutrophils are activated but don’t work/die by killing), lymphadenopathy+/- hepatosplenomegaly
Investigation and treatment for chronic granulomatous disease
- Investigation for chronic granulomatous disease
- Nitoblue tetrazolium (NBT) test - changes colour from yellow to blue if there is hydrogen peroxide produced by activated neutrophils
- Dihyro-rhodamine (DHR) flow cytometry - fluorescence if rhodamine interacts wth H2O2
Treatment - IFNy to * increase the macrophage ability for killing by oxidative pathway (IFNy therapy)
4 examples of primary immune phagocyte deficieies
- Kostmann (congenital neutropenia)
- Leukocyte adhesion deficiency (CD18-beta2 integrin subunit deficiency that is needed for form LFA- 1 on neutrophils)
- Chronic granulomatous disease (no oxidative killing)
- IL12/IFNy deficiency
IL-12, IL12R, IFNy or IFNyR deficiency
- IL12-IFNy network - particularly impt for mycobacterial infection and salmonella
- Infected macrophage produce IL12
- IL12 induce T cell to produce IFNy
- IFNy feeds back to macropahge to produce TNF and free radical
- Activate NADPH oxidase (oxidative killing) by both macrophage and neutrophils
Symptoms of phagocyte deficiency
- Recurrent infections for extracellular pathogens - skin and mouth
- Bacterial (S.aureus, Enteric bacteria)
- Fungal (Candida albicans, Aspergillus fumigateurs and flavus)
- Mycobacterial infections (particularly so if impaired cytokine network)
- Mycobacterium TB
- Atypical mycobacteria
Treatment principles of phagocyte deficiencies (2)
- Agressive managent of infection
- Infection prophylaxis
- Septrin - Abx
- Itraconazole - anti-fungal
- Oral/IV Abx as needed
- Infection prophylaxis
- Definitive therapy
- Haematopoietic stem cell transplant
- For chronic granulomatous disease (CGD), you can give IFNy to increase the macrophage ability for killing by oxidative pathway (IFNy therapy)
- Haematopoietic stem cell transplant
Classical NK deficiency (name the genes mutation)
- Abnormalities described in GATA2 or MCM4 genes in subtypes 1 and 2
Functional NK deficiency (name the gene mutated)
- Abnormality described in FCGR3A gene in subtype 1
Clinical presentation of NK deficiency
- Frequent virus infection
- herpes (Simplex, Varicella zoster, Epstein Barr, CMV)
- Papillomavirus infection
Name the classical complements
C1, 2, 4
What condition is associated with classic complement deficiency?
SLE
- Complement fragments promote clearance of apoptotic/necrotic cells by phagocytes
- Deficiency results in increase load of self antigens, particularly nuclear components
- Which promote auto-immunity and formation of immune complexes
- Fragments also promote clearance of immune complexes by erythrocytes, by making them soluble
- Deficiency results in deposition of immune complexes stimulating local inflammation
- Clinical features: SLE
- usually very severe skin disease
- Almost all patient with C2 deficiency have SLE
Deficiency of MBL
What problems does it cause?
- 30% of all individuals are heterozygote for mutant protein
- 6-10% have no circulating MB
- Do not seem to cause significant problem unless there is another additional immune impairment on top of MBL deficiency
What problems does deficiency of Factor B, I, P (alt complement pathway) cause?
- Inability to mobilise complement rapidly against bacterial infections (recall that classical pathway is slower due to need for acquired immunity cos antibodies needed)
- Clinical features
- Recurrent infections with encapsulated bacteria
- Very rare
C3, C5-C9 deficiency cases? (3 classic infection)
- Severe susceptibility to bacteria infections
- Neisseria meningitis
- strep pneu
- H. influenza
2 cause son secondary complement deficiencies
Acute SLE
Nephritic factors
Acute lupus (SLE) causes persistent production of immune complexes leading to consumption of classical complements
- Nephritic factors are auto-antibiotics against components of the complement
- Nephritic factors stabilise C3 convertases resulting in C3 activation and consumption
- Often associated with glomerulonephritis (classical membranoproliferative)
- May be associated wth partial lipodystrophy (lose fat on the upper half of body)
Name the 2 functional tests for complement activity
CH50 - for classical pathway
AP50 - for alternative pathway
Hereditary angioedema is deficient in which complement
C1
Presentation of Familial Mediterranean Fever
Periodic fevers lasting 48-96 hours
Abdo pain (peritonitis)
Chest pain (pleurisy and pericarditis)
Arthritis
Management of femilial mediterranean Fever
- Colchicine 500μg bd: binds to tubulin in neutrophils & disrupts neutrophil function (including migration & chemokine secretion)
* Same as used in gout to limit inflammation by neutrophil- Anakinra (IL-1R antagonist)
- Targets the cytokines coming out of the inflammasome complex
- Etanercept (TNF-α inhibitor)
- Type I IFN
- Anakinra (IL-1R antagonist)
3 types of monogenic autoimmune dx
- Impaired tolerance - APECED (cannot present self antigen at thymus to lymphocytes, failure of positive central selection)
- Treg abnormality - IPEX (mutation in Foxp3 = no T-reg)
- Impaired lymphocyte apoptosis (mutation in Fas pathway, lymphocytes, including self-selecting lymphocytes cannot die, can lead to lymphoma)
Crohn’s disease - role of NOD2 (genetic polymorphism)
NOD2 is a gene located on Chr16 that encodes for IBD1 protein.
When mutated, it increases the risk of getting Crohn’s.
1 mutated copy = 1.5-3x likely to get CD
2 mutated comes = 44x likely to get CD
But in itself alone, is not sufficient to get CD. Hence 2xNOD2 mutations does not automatically give you Crohn’s. (genetic polymorphism of mutated NOD2 gives you susceptibility)
To get CD, also needs combination of environmental factors and other genetic influences
NOD2/IBD1 is found in the cytoplasm of myeloid cells i.e macrophages, neutrophils etc. It recognises microbial MURAMYL DIPEPTIDE to trigger NFkB and inflammation.
In Crohn’s this + other factors gives you pro-inflammatory cytokines in/around crypts. Leads to non-caseating granulomas and mucosal ulceration.
Mx of Crohns (4)
Steroids
Anti-TNFa - infliximab, adalimumab
Azathioprine
Anti IL-12/23 - ustekinumab
3 examples of mixed pattern auto inflammatory and autoimmune dx
AS
psoriatic arthritis
Behcet’s syndrome
AS: * Enhanced inflammation occurs at specific sites where there are _____
Enhanced inflammation occurs at specific sites where there are high tensile forces (entheses - sites of insertions of ligaments or tendons to bone)
Presentation of Ank Spond.
Young <40 with early morning stiffness
Typical patient: Young man <30 with gradual onset low back pain worst at night, spinal stiffness in morning relieved by exertion. Pain radiates from sacroiliac joint to back
- Progressive loss of spinal movement (spine flexion - kyposis and neck hyperextension - ? posture)
- Enthesitis: Achilles tendonitis, plantar fasciitis of tibial and ischial tuberosities and at iliac crest
- Acute irits: may lead to blindness
- Anterior CP due to costochondritis
- Fatigue
Key complications: (7A)
- Atlanta-axial subluxation - due to dentate ligament of connective tissue dysfunction
- Anterior uveitis/Acute iritis
- Autoimmune arthritis
- Amyloidosis
- Aortic regurg
- Achilles tendonitis, plantar fasciitis
- Apical lung fibrosis
Tx for ankylosing spond
- Non-steroidal anti-inflammatory drugs
- Immunosuppression (need to target the cytokine pathway)
- Anti-TNFα
- Anti-IL17
- Anti-IL12/23
HIV virus structure (genes and proteins)
2x ssRNA, retrovirus, 20-sided capsid with membrane around it
9 genes, 15 proteins
env → gp120 and gp41
pol → 3 enzymes: reverse transcription, integrate and aspirate protease
gag → p24 (capside formation)
How HIV infect target cells
gp120 binds to CD4
co-receptors of CCR5 and CXCR4 on target cells
gp41 fusion of virus into cell
3 modes of HIV transmission
Sexual - via mucosal surfaces esp when there is co-current other STI which already weakens mucosal barrier
Vertical - mother to child during brith or breast milk
Infected blood - sharing of needles, blood transfusion
Describe the body’s immune response (both innate and adaptive) to acute HIV infection
- Natural immunity kicks in within hours of infection
- Inflammation, non specific activation of macrophages, NK cells and complement
- release of cytokines and chemokine
- stimulation of dendritic cells via toll like receptor
BUT HIV also cause NK cells to up regulate inhibitory receptors which makes them anergia/useless
- Acquired immunity (B cells)
- DC cells presents antigen to B cells
- B cells undergo maturation and class switching at lymph nodes with hope from follicular T cells
- IgG antibodies against gp120 and gp41 produced (protective0
- IgG antibodies against p24 also produced
BUT HIV remains infectious even when covered by antibodies. Once it is coated, it can now enter cells via the Fc portion of antibodies
- Acquired immunity (T cells)
- CD4 needed to signal and help other immune cells. They are selectively lost later
- CD8 cells can kill HIV infected cells but without CD4 helper, naive CD8 T cells cannot be primed and become effector T cells
- lost of CD4, CD8 and B cell memory
Eventually APC such as dendritic cells and monocytes are also killed by HIV = no more antigen presentation to activate adaptive immune system
Effect of HAART on HIV viral load and CD4 counts
- Monitored by two markers
- Marker 1: Suppression of viral load
- Marker 2: CD4 levels rising
- Initial CD4 rise - memory T cells redistributed
- Later CD4 rise is thymic naïve T cells → thymus regeneration
Patterns of untreated HIV disease progression (4 types of people)
85% typical progressors AIDS within 10 years
10% rapid progressors AIDS within 3 years
<5% long term non-progressors - no AIDS but infected
Exposed seronegative - no HIV despite exposure
Describe the clinical course of untreated HIV in terms of viral load, CD8 and CD4 from acute infection to long term
- During primary infection → viral load increases
- As the virus peaks → damage decline in CD4 lymphocytes (primary target of virus)
- But at the same time, CD8+ kicks in and have effector responses
- Hence for a while, the CD8+ seem to be effective against the target (direct killing or soluble mediators) as the oral load drops and pts is asymptomatic
- But virus (while being hunted by CD8) is still targeting the CD4 cells which is needed for full CD8 function
- When the CD4 falls below <200cells/ul, then the CD8 becomes ineffective → AIDS
- Opportunistic infections and malignancies
Steps in HIV viral replication in a cell
- Attachment/Entry
- Reverse Transcription & DNA Synthesis (RNA → DNA)
- Integration (viral DNA → Host DNA)
- Viral Transcription (Viral DNA → mRNA by host mechanisms)
- Viral Protein Synthesis
- Assembly of Virus & Release of Virus
- Maturation (Chopping up polypeptide etc continues even after the virus is released fro the cell)
Diagnosis HIV methods
Detection of HIV-1
* The HIV antibody ELISA is a screening test and the HIV antibody Western blot is a confirmatory test.
Detection of viral load via PCR
* The initial baseline plasma viral load (that is when the patient is first monitored for virus number) is a good predictor of the time it will take for AIDS to appear.
CD4 counts (to monitor disease severity and progression) * The onset of AIDS correlates with the diminution of the number of CD4 T cells (<200cells/ul) - characterised by opportunistic infection by bacteria and cancers
HIV-1 resistance testing
- Two established assays for measuring resistance to antiretroviral drugs
- Phenotypic: Viral replication is measured in cell cultures under selective pressure of increasing concentrations of antiretroviral drugs – compared to wild-type
- Genotypic: Mutations determined by direct sequencing of the amplified HIV genome (so far limited to sequencing of RT and P) - Both assays are available commercially (expensive)
What is the role of HAART in HIV? What drugs are typically in a HAART regimen.
- The use of combination regimens of anti-retroviral agents has allowed:
- Substantial control of viral replication
- Increase in CD4 T cell counts
- Improvement in their host defenses with a dramatic decline in opportunistic infections and deaths.
- HOWEVER, HAART does not eliminate the virus from the patient due to a reservoir of HIV in resting CD4 T cells and CD4 MO
- Only prevent viral replication
Which HAART regimen?
- 3 drugs from at least 2 different classes
- Two drugs backbone = one or more binding agents
Give examples of drug for HIV/HHART
HIV entry Fusion inhibitors * Enfuviritide (T-20) CCR5 co-repcetor antagonists * Maraviroc
Pre-transcriptional NRTI - nucleoside RTI * Zidovudine * Lamivudine (3TC) * Didanosine (ddl) * Stravudine (d4T) * Abacavir (ABC) * Emtricitabine (FTC) Nucleotide RIT * Tenofovir (TDF) NNRTI * Nevirapine (NVP) - SE hepatitis and rash * Efavirenz (EFV) - SE CNS effects * Etravirine * Rilpirivirine
Post-transcription Integrase inhibitors * Raltegravir * Elvitegravir Protease inhibitors * Lopinarvir (LPV) * Ritonavir (RTV) - P450 inhibitors. Given with other Pis to reduce metabolism and boost effectiveness * Fosamprenair * Darunavir (DRV) * Atazanavir - boosted PI * Saquinavir * Indinavir * Tipranavir All PI causes hyperlipidaemia, fat redistribution and T2DM
Important side effects of some HIV drugs
- Tenofovir
- Efavirenz
- Abacavir
- Atazanavir
- Tenofovir: can affect kidneys
- Efavirenz: insomnia/vivid dreams, psychiatric symptoms
- Abacavir: need HLA B*5701 test first due to risk of hypersensitivity
- Atazanavir: jaundice.
When to initiate HAART? Which HAART regimen?
- New BHIVA 2016 guidelines suggest all patients on HAART regardless of CD4 count as they get better outcomes. Previously only when CD counts are <350 or <200
Choices: 2 NRTIs + PI (or NNRTI)
Limitations and complications of HAART regimens
- Effective HAART does not eradicate latent HIV-1 in the host
- Potential for immunotherapy
- Fails to restore HIV-specific T-cell responses
- Is dogged by the threat of drug resistance
- Significant Toxicities
- High pill burden
- More drugs needed to control the SE of HIV-drugs
- Adherence problems
- Quality of life issues
- Cost (~40%)
Vaccination herd immunity formula
1/R0 where R0 i the average number of people 1 infected person can infect on average
3 situations for vaccinations
Young
Travel - HepB/HepC/TB/VZV/typhoid/rabies/cholera
Elderly - Pneumo PPV, flu, shingles
Principles of why vaccines work
Immune memory
Exposure of immune system → exquisite specificity
Memory B and T cells = more easily activated and long-lived
Persistence of existing IgG
4 methods of immune-boosting
- Vaccination
- Replacing missing component e.g. BMT/antibodies/T cells
- Cytokine therapy
- Block immune checkpoints to allow greater activation of T cells
Ipilimumab -MOA what disease is it used for
anti-CTLA4
CTLA4 is an T cell inhibitor. Antibody to it allows T cell activation
Used in advanced, met melanoma
Pembrolizumab & nivolumab - MOA and what disease is it used for
anti-PD1
PD1 ligand is expressed by APC and tumour cells
Activation of PD1 = negative regulator of T cell
Pembrolizumab and nivolumab
Cytokine therapy how does it work and what types are there/for what disease
Boost immune response to cancer and some pathogens
IFNa
- HepB, HepC, Kaposi
- hairy cell leukaemia, CML, multiple myeloma
IFNb
- relapsing MS
IFNy
- Chronic granulomatous disease
How does general antibody replacement work? Where does it come from and how is it administer? how frequent
Plasma from healthy donors (screened and irradiated) are pooled
All the Ig present in the blood are administered by IV or SC to the recipient every 3-4 weeks
What disease can be treated by general antibody replacement
Primary immune def - Bruton’s, hyperIgM, CVID
Secondary antibody def - Haem cancers e.g. CLL/multiple myeloma
EBV T Cell replacement - what is this a treatment for?
Patients who are post BMT who are unable to control persistent EBV infection causing EVG related B cell lymphoproliferative disease
Immunoboosting therapies - T cell replacement (what 2 types of viral specific T cell replacements are there?)
CMV → for CMV retinitis (pizza topping chorioretinitis)
EBV-specific CD8 T cells (EBV Burkit’s lymphoma)
Explain the 3 MOA of steroids
- Phospholipase A2 inhibitor - prevent production of prostaglandin and leukotriene
- Inhibits phagocyte (e.g. neutrophil) migration and function - transient neutrophilia
- Inhibits lymphocyte function - sequestrated in lymphoid tissue (CD4 > CD8 > B)
Steroids are synthetic glucocoticosteroids which has/has no mineralocorticoid function. The equivalent endogenous dose is ____
NO mineralocorticoid activity
5-7.5 mg is the equivalent to endogenous steroid produciton
SE of steroids
Metabolic
- diabetes, obesity, Cushingnoid, abnormal lipids, abnormal LFT, osteoporosis
Others
- cataracts
- glaucoma
- AVN
- peptic ulcers
- myositis
Name 3 anti proliferative drugs that can be used in immunosuppression
Cyclophosphamide
Azathioprine
Mycophenolate mofetil
MOA of cyclophosphamide
Alkylates guanine in DNA and stop cell proliferation
Inhibits B>T cells
At high doses inhibit all rapidly proliferating cells
SE of anti proliferative drugs e.g. cyclophosminde, azathioprine and myophenolate mofetil
Bone marrow suppression
Infection (worst with cyclophosmiade_
What enzyme polymorphism should be checked before prescribing azathioprine
TPMT
Polymorphism can mean some patient cannot metabolise drug → toxic accumulation
MOA of azathioprine (3)
Metabolised by liver into 6 mercaptopurine
1. Which blocks de novo purine synthesis
2. Inhibits T cell activation
3. Inhibits T cell proliferation
Drug is then broken down by TPMT
T>B cell (same as mycophenolate mofetil) but different from cyclophosmiade which is B>T
The enzyme in de novo purine synthesis is PAT (PPRP amide transferase?)
The enzyme lost in Lesch Nylan in salvage/recycling pathway is HGRT
Indications for azathioprine
Transplant
Autoimmune
Auto inflammatory
IBD
Indications for cyclophosphamide
Vasculitis
CTD e.g. severe, neuropsych SLE
Anti-cancer
Indications for mycophenolate mofetil
Alternative to azathioprine for transplant
Alternatie to cyclophosmiade for vasculitis and autoimmune conditions
MOA of mycophoenolate mofetil
Blocks de no nucleotide synthesis (v guanine nucleoSIDE synthesis in azathioprine)
T>B
Specific SE associated with cyclophosphamide
Haemorrhage cystitis - Due to toxic metabolic acrolein being excreted in the urine
And also hence bladder cancer (hame cancer from bone marrow suppression) and non-melanoma skin ca
Cyclophosphamide has the worst SE wrt to infections what prophylaxis is needed?
PCP (pneumocystis jiroveci pneumonia) with co-trimoazole
What specific infections is taking mycophenolate mofetil at risk of
Herpes reactivation and PML (from JC virus)
Progressive multifocal leukoencephalopathy
Ustekinumab
Anti-p40 subunit of IL12 and IL23
used in psoriatic arthritis
Secukinumab
anti-IL17a
Used in psoriatic arthritis and ankylosing spondylitis after anti-TNFa
Denosumab
Anti-RANKL
Osteoporosis
Tocilizumab
Anti-IL6 Castleman syndrome (IL6 producing tour)
Natalizumab
Anti-a4 integrin
MS
Rituximab
Anti-CD20
Targets mature B cell but not plasma cells (hence low risk of infection)
Used in lymphoma, RA and SLE
Do not increase malignancy but exacerbates CVS disease
Abatacept
Fusion protein of IgG Fc and CTLA-4
Binds CD80 and CD86 to prevent T cell priming
Used in RA (IV every 4 week) or SC weekly
Basiliximab
Anti-CD25 (IL-2Ra chain)
Inhibits T cell proliferation
Used in prophylaxis of allograte rejection - iV before and after transplant
Tofacitinib
JAK inhibitor
used in the state for RA
Apremilast
PDE4 inhibitor, reduces cAMP and cytokine production
Used in psoriatic arthritis
Cyclosporin and tacrolimus
Inhibits calcineurin and hence reduces IL2 production
SE of cyclosporin and tarcolimus
nephrotox, neurotic, hypertension
Cyclosporin - gum hypertrophy and hirsutism
Tarcolimus - diabetogenic
What is plasmapheresis
Removal of pathogenic antibody in pt blood by passing it though a cell separate. Cells returned to pt but ab in plasma removed
Used in severe antibody mediated dx e.g. Goodpastures (anti-GBM) and severe MG (anti-ACh) - dx due to type 2 hypersensitivity
Pembrolizumab and nivolumab
anti-PD1 (PD1 is T cell negative regulator)
Hence pembrolizumab and nivolumab activate T cell and boost immune system
Used in advanced melanoma
Ilipimumab
CTLA4 inhibitor
Increases T cell activation
used in advanced melanoma
MOA of calcinuerin inhibitors
E.g. cyclosporin and tacrolimus
Activation of TCR → increase in intracellular Ca from ER
Ca binds to calmodulin
Cal modulate increase calcineurin which binds to NFATc
NFAT (transcription factor) up regulates transcription of IL2
Anti-thymocyte globulin + SE
Rabbit Abs against human thymocyte globulin
Depletes host T cell
Used n allograft rejection, daily IV infusion
SE: infection, malignancy
leucopenia
infusion reaction
Explain the oral v skin allergy concept
- Oral routes promote immune tolerance while skin induces IgE sensitisation
- Gut: Protein are partially degraded by digestion process → peptides formed of lower allergenicity. IgG responses formed to dietary protein which induced tolerance (Treg, IL10 and TGFb)
- Skin: when there is skin barrier disruption (e.g. filaggrin predisposes to more leaky skin binding), the pathogen/allergen gains access to the dermis. Activated skin dendritic cells are very potent in activating T cells. T cells help B cells to activate to form IgE responses → dermatitis.
- Dermatitis in children if unchecked in children is associated with future allergic disorder (allergic march)
- If the skin barrier is intact, no penetration of allergen into dermis and hence no immune response.
- Evidence LEAP study: Children at high risk of peanut allergy – early introduction of peanut into the diet reduces the risk of allergic responses. The likely explanation is that peanut is in the gut first, so an IgG response is formed before the IgE response.
Clinical presentation of true allergy + common symptoms that are NOT due to allergy
- Symptoms occur within 3min or ≤3hrs after allergen exposure
- Typically ≥2 organ systems are involved:
- Skin: angioedema (swelling of lips, tongues, eyelids), urticaria (wheals or ‘hives’), flushing & itch
- Respiratory: cough, SOB, wheeze, sneezing, nasal congestion & clear discharge, red itch watery eyes
- GIT: nausea, vomiting and diarrhoea
- Vasculature & CNS: symptoms of hypotension (faint, dizzy, blackout), sense of
impending doom - Symptoms are reproducible after every exposure (don’t vary with time or dose or concentration of allergen)
- May be triggered by cofactors (e.g. exercise, EtOH, infection)
- Note symptoms reported by patients which are NOT assoc. with IgE allergic reactions:
- Fatigue
- Migraine - food related migraine is pharmacological effect not IgE mediated
- Recurrent episodes of abdominal pain, diarrhoea, constipation and bloating
- Hyperactivity
- Depression
- Confusion
- Variation of symptoms with dose and route of allergen
Investigations for ?allergy (both elective and acute)
- Skin prick test:
- Serum specific IgE test (RAST)
- Component-resolved diagnostics (CRD)
- oral Ag challenge test for food and drug allergy
- Serum mast cell tryptase levels
Explain how a skin prick test is done
- Discontinue antihistamines ≥48hrs before test
- Expose patient to standardised solution of allergen extract through skin prick to forearm
- Use standard skin test solutions, +ve (histamine) & -ve controls (diluent)
- Measure local wheal & flare response to controls & allergens
- +ve test if wheal ≥ 3mm greater than -ve control
- More sensitive & specific than blood tests to diagnose allergy in routine clinical practice. Considered to be gold standard to support a diagnosis of allergy in routine allergy practice
Describe how a RAST test is done
- Allergen bound to sponge in plastic cap & patient’s serum is added
- Specific IgE (if present) binds to allergen
- Fluorescent tagged anti-IgE Ab is added
- Amt.of IgE/anti-IgE is measured by fluorescent light signal
- Much more expensive than skin prick test (£15 for a single test)
Describe component-resolved diagnostics (CRD)
- Blood test to detect IgE to single protein components
- Useful for diagnosis of food allergies e.g. peanut, hazelnut (established) and milk (emerging)
- May reduce need for food challenges
- Two main types of food allergens:
- Heat and protease labile, these allergens tend to cause low or minimal symptoms confined to oral cavity → safe for food challenge to take place
- More stable allergens – resist enzymatic breakdown → systemic symptoms or anaphylaxis → food challenge not safe, allergen avoidance
Describe Ag challenge test
- Gold standard for food and drug allergy - double blind placebo (gold standard) or open challenge
- Increasing vol. of food/drug ingested
- Must take place under close medical supervision (expensive) due to risk of severe reaction
- Difficult to interpret mild symptoms
Describe levels of serum mast cell tryptase in anaphylaxis
- Peaks at 1-2hrs & returns to baseline by 6-12hrs
- Failure to return to baseline may indicate systemic mastocytosis (clonal disease of mast cells)
- Serial measurement of serum tryptase (a highly specific marker for mast cell degranulation)
- Take samples 1, 3 & 24hrs post-episode of anaphylaxis
- The rise in tryptase concentration is directly proportional to fall in BP
- Blood histamine not very practical in routine practice
- Tryptase: pre-formed protein found in mast cell granules
not useful for food induced anaphylaxis
4 mechanisms of anaphylaxis
IgE - mast cells → histamines + platelet activating factor
IgG - macrophages/neutrophiles → histamine + platelet activating factor
Complement - mast cells/macrophages → PAF + histamine
Pharmacological - mast cells → leukotrienes and
NB IgG can induce anaphylaxis but require very high concentration of antigen and the antigen must be introduced systematically for it to cause anaphylaxis histamine e.g. blood transfusions, biologics, IgG transfusion
Emergency management of anaphylaxis
- IM adrenaline 500ug → outer aspect of thigh and repeat if needed
- Adjust body position: sit up if SOB, supine if hypotension, lie on side if unconscious
- Oxygen 100%
- Fluid replacement
- Inhaled Bronchodilators
- Hydrocortisone 100mg IV (prevent late phase response)
- Can get a late rebound, this has a slower mechanism of action and isn’t given to deal with the acute effects
- Chlorpheniramine 10mg IV (for skin rash)
- Get help, don’t panic
Adrenaline MOA in anaphylaxis
- α1 receptors: causes peripheral vasoconstriction, reverses low BP and mucosal oedema
- β1 receptor: increase heart rate and contractility and BP
- β2: relaxation of bronchial smooth muscle & reduces release of inflammatory mediators
Follow-up management of anaphylaxis
- Referral to:
- Allergy/immunology clinic
- Qualified dietician (if food-induced anaphylaxis)
- Venom immunotherapy & drug desensitisation as appropriate
- Investigate the cause of anaphylaxis
- Written information sheet on the following;
- Recognition of symptoms
- Avoidance of identifiable triggers
- Indications for self-treatment with an Epipen
- Prescription of emergency kit to manage anaphylaxis
1. Epipen: contains adrenaline (300μg for adults, 150μg for children) + prednisolone 20mg OD
2. Antihistamine tablet: cetirizine 10mg OD
3. Must call ambulance & attend A&E after using emergency kit
4. All patients should be prescribed 2 pens - Copy of management plan and training for patient, carers, school staff and GP+ Implement patient’s management plan in nursery and school
- Advise patients to acquire a Medic Alert bracelet
- Review patients to ensure that they understand their disease and can use their Epipen
- Utilise patient support groups i.e. AnaphylaxisCampaign
Adverse Reactions to Food (3 types)
- Food intolerance: non-immune reactions which include metabolic, pharmacological & unknown mechanisms
- Food poisoning (e.g. bacterial, scromboid toxin)
- Enzyme deficiencies (e.g. lactose intolerance)
- Pharmacological (e.g. caffeine, tyramine)
- Food aversion
- Fads, eating disorders
- Food allergy:
- IgE mediated reactions (e.g. anaphylaxis, OAS)
- Cell mediated (e.g. coeliac)
- IgE and cell mediated (e.g. atopic dermatitis)
3 main management strategies for allergies/anaphylaxis
- Avoidance:
- Education about food labelling, interactions with restaurants & school
- Nutritional input for dietary balance & growth in children
- Acknowledge anxiety & potential bullying: mental health support if required
- Emergency mx
- As with anaphylaxis
- Ensure well-controlled allergic asthma
- Prevention:
- Breast feeding: strong preventer of allergy
- LEAP study showed that delayed introduction of peanuts in high risk children (atopic dermatitis, egg allergy) reduced development of peanut IgE sensitisation & allergy
Question 1: A 18 years old lady with a history extensive eczema who is unable to stop taking anti-histamine medication. What is the most appropriate test to look for IgE sensitisation?
→ RAST - rapid antigen sensitivity blood test
Question 2: A 60 year old female with hypotension and skin rash under general anaesthesia. What is the most appropriate test to diagnose anaphylaxis ?
→ Mast cell tryptase
Question 3: A 15 year old with a history of asthma and hayfever who notices increasing cough and wheeze shortly after eating peanuts. What is the most appropriate initial diagnostic test ?
→ Skin prick/Serum specific IgE test (RAST)
A 55 year old man with a 6 hour history of lip and tongue angioedema involving lips and tongue who is taking an ACE inhibitor and calcium channel blocker for hypertension. Clinical examination show a pulse of 75, blood pressure 150/90, respiratory rate of 18/min and oxygen saturation 98% on air. What is the most likely diagnosis?
→ ACEi angioedema
A 35 year old man with a history of spring time hayfever and immediate lip tingling and swelling immediately after eating and apples.
Options:
* IgG4 subclass deficiency
* Cross reactive IgE sensitisation between hay fever and apple allergens
* Apple-hay fever immune complex disease
* Increased Th17 immune response to apple allergen
* Food aversion disorder
What is the most likely explanation for IgE hypersensitivity?
- Cross reactive IgE sensitisation between hay fever and apple allergens
DDx of basophilic stripping on blood film
- Basophilic stippling aka Punctate basophilia refers to an observation found when observing a blood smear in which erythrocytes display small dots at the periphery. These dots are the visualization of ribosomes and can often be found in the peripheral blood smear, even in some normal individuals
- Aggregated ribosomal material
- Beta thalassaemia trait
- Lead poisoning
- Alcoholism
- Sideroblastic anaemia
DDx of Hypersegmented neutrophil on blood film
- Maximally 5 segments in neutrophils
- Megaloblastic anaemia - reflects impaired DNA synthesis
- Associated with
- B12 deficiency
- Folate deficiency
- Drugs
Describe target cells on blood film. and DDx
- Codocytes - relatively high surface area: volume ratio
- AKA Sodosopiacytes
- Associated with IDA, thalassaemia, hyposplenism, liver disease
- Should be removed by spleen but if present in blood = abnormal
Howell-Jolly bodies
- Nuclear remnant visible in red cells
* This is a sign of hyposplenism
- What are the clinical features of anaphylaxis? (10 for complete answer)
- Skin &/or mucosal tissue: hives, itch, swollen lips, tongue, uvula, flushing
- Respiratory compromise: SOB, wheeze (lower airway bronchoconstriction), stridor (upper airway), fall in PEF, hyperaemia, angioedema
- Reduced BP or assoc. symptoms: collapse, syncope, incontinence, MI
- Persistent GIT symptoms: crampy abdominal pain, vomiting, diarrhoea (from increased mucus production in the gut)
- Neuro: impending sense of doom, LOC
Immediate management of anaphylaxis
- ABCDEFG
- Patients may require respiratory support
- Intubation may be required for severe bronchoconstriction
- Tracheostomy if develops upper respiratory tract obstruction (e.g. laryngeal swelling, or severe swelling of the tongue)
- Oxygen by mask
- Improve oxygen delivery
- Adrenaline im (1: 1000 0.5mg for adult and may repeat)
- Acts on B2 adrenergic receptors to constrict arterial smooth muscle
- Increases blood pressure
- Limits vascular leakage
- Bronchodilator
- Repeat if necessary
- Acts on B2 adrenergic receptors to constrict arterial smooth muscle
- Intravenous anti-histamines (10mg Chlorpheniramine)
- Acts to oppose the effects of mast-cell derived histamine
- Nebulized bronchodilators
- Improve oxygen delivery through bronchial dilatation
- Intravenous corticosteroids (Hydrocortisone 200mgs)
- Systemic anti-inflammatory agent.
- Effect takes about 30 minutes to start, and does not peak for several hours.
- Important in preventing rebound anaphylaxis (2nd episode)
- Intravenous fluids
- Increase circulating blood volume and therefore increase blood pressure
Adults v paeds causes of anaphylaxis
- Causative agent:
- Children: food more common
- Adults: drugs & venom more common
- Frequency of organ involvement: (adults v kids)
- Skin (most frequent): 84% - Almost all patients with anaphylaxis will have skin involvement (itch, erythema, urticaria, angioedema)
- CVS (more often in adults): 72% - (faint, lightheaded, collapse, LOC)
- Respiratory (more often in children): 68% - (asthma, laryngeal oedema)
What are some common causes of anaphylaxis
Common causes of anaphylaxis
- Foods
- Peanuts
- Tree nuts
- Fish and shellfish
- Milk
- Eggs
- Soy products
- Insect stings
- Bee venom
- Wasp venom
- Chemicals, drugs and other foreign proteins
- Penicillin and other antibiotics
- Intravenous anaesthetic agents, eg suxamethonium, propofol
- Latex
- Only a limited number of foods cause true food allergy
- Distribution of food allergy is different in children compared to adults
- e.g. wheat is more common in children
- Shellfish allergy is more common in adults
There are two types of latex allergy
- Type I hypersensitivity
- Acute onset of classical allergic symptoms after exposure e.g. wheeze, urticaria, angioedema, anaphylaxis.
- Spectrum of severity
- Mucosal route is associated with more severe reactions
- Different rubber products vary significantly in their allergenic content
- Type IV hypersensitivity
- Contact dermatitis
- Usually affect hands (glove usage) or feet (due to rubber in footwear)
- Mainly due to rubber additives eg thiuram rather than latex itself
- This is T- cell mediated. CD4+ cells activates CD8+ cells to destroy the antigen and release cytokines.
- Symptoms occur 24-48 hours after exposure (much later than in IgE mediated reactions).
- Itch ++
- Rash, well-demarcated, often flaky
- Not responsive to anti-histamines
Why do adults with latex allergy may also have food allergy?
- Type I hypersensitivity to latex; cross reactivity with chitinase containing foods
- Avocado
- Apricot
- Banana
- Chestnut
- Kiwi
- Passion fruit
- Papaya
- Pear
- Pineapple
What disorders are associated with recurrent meningococcal meningitis?
- Immunological
- Complement deficiency
- Recurrent infection with encapsulated organisms
- Neisseria meningitis,
- Gonococcus, H influenza B, pneumococcus
- Recurrent infection with encapsulated organisms
- Antibody deficiency
- Recurrent bacterial infections, especially of upper and lower respiratory tract
- Complement deficiency
- Neurological
- Any disruption of blood brain barrier
- Occult skull fracture
- Hydrocephalus
- Any disruption of blood brain barrier
- Generally suggested that adults with sporadic meningococcal disease should be screened for complement deficiency
How would you manage a patient with complete C7 deficiency
- Meningovax, pneumovax and HIB vaccines
- Daily prophylactic penicillin
- High level of suspicion for infection
- Can’t just give him C7, it is highly labile and would just get degraded.
- Ideal is gene therapy but not possible as of yet
How does SLE causes complement deficiency?
- Immune complexes bind to C1q and activate classical pathway
- Complement is consumed
- Low levels of C4 and C3 complement suggest SLE is active
- ESR and dsDNA titre also reflect activity of disease
histologically SLE kidneys
- Renal biopsy
- Diffuse proliferative nephritis
- Immune complex and complement deposition
- Lumpy bumpy deposition
1 immune suppression drug that makes SLE worse
NB: sulphasalazine is known to make lupus worse.
Diagnosing SLE
Diagnosis
SLICC criteria (2012)
* Patient must have biopsy proven lupus nephritis with positive ANA or dsDNA OR
* patient must have four criteria including at least one clinical + one immunological criteria
3 best tests
1. Anti-dsDNA antibodies
2. Complement: Low C3 and C4 (SLE consumes complement)
3. ESR (high) but CRP normal. If CRP is high think infection, serositis or arthritis
Also do
* BP
* urine for casts or protein (lupus nephritis)
* FBC, U&E, LFT
* Skin or renal biopsies may be diagnostic
Management for SLE
Management
- treat whatever organs that are affected
- mild: PRN anlagesia, hydroxychloroquine (first line)
- Moderate: pred, hydroxychloroquine (DMARD), AZA/metho/mycophenolate mofetil (anti-T cells)
- Severe: DMARD =/- steroids, biological agents (esp rituximab to deplete B cells and reduce auto-antibodies)
- life-threatening: cyclophosphamide (non-specific toxic immunosuppressant), plasmapheresis
New therapy for SLE
- Low dose interleukin-2 therapy (IL-2)
* IL-2 promotes T-cell growth. At low dose, it helps to expand T-reg because they have highest affinity for IL-2
The two most common clinical manifestations of anaphylaxis?
angioedema and urticaria
Why do you give IV corticosteroids to prevent in cases of anaphylaxis
rebound anaphylaxis
Adults with recurrent meningococcal disease should be screened for defects in which immune system pathway
complement especially alternative and final pathway
What is serum sickness
Common reaction of pencillin
- Mechanism
- Penicillin can bind to cell surface proteins
- Acts as a neo-antigen: stimulates a very strong IgG antibody response
- Individual is sensitised to penicillin.
- This is not anaphylaxis because it is IgG and NOT IgE
- Subsequent exposure to penicillin stimulates
- Formation of immune complexes with circulating penicillin
- The production of more IgG antibodies.
- Immune complexes are deposited in small vessels, affect the glomerulus and lead to infiltration of macrophages and neutrophils.
What further investigations would you do to confirm the diagnosis of serum sickness in response to pencillin? (share some similarities with SLE)
- Low serum C3 and C4
- Indicative of classical complement pathway activation
- (Immune complex measurements unreliable)
- Specific IgG to penicillin
- Can be performed if specifically indicated, but takes time
- Characteristic biopsy features (skin, kidney)
- Infiltration of macrophages and neutrophils
- Deposition of IgG, IgM and complement
Managing a patient with serum sickness
- Discontinue penicillin immediately → self-limiting after
- THIS IS THE MOST IMPT BIT
- Decrease systemic inflammation with corticosteroids
- Ensure appropriate fluid balance
Management of Bruton’s
- Immunoglobulin replacement therapy
- Pooled serum IG
- Administered every 3 weeks
- Indefinite treatment
- Stem cell/bone marrow transplantation would be a more permanent treatment
No point vaccinating
- 64 yr old lady is seen in A+E after slipping and injuring her left hip when getting out of the bath.
- Other problems
- Persistent back pain and generalised lethargy for 12 months
- Three episodes of pneumococcal pneumonia in last 2 years
- Post-menopausal – on HRT
- Physical examination
- Swollen, tender hip with marked limitation of movement
- Clinically anaemic
X-ray show pepper pot skull with decreased bone density
Bloods show normal ALP, with normocytic anaemia
What is your DDX?
- Multiple myeloma
- Osteoporosis and Sjogren’s syndrome
- Osteoporosis and SLE
Symptoms of multiple myeloma
CRAB Calcium - high Renal - bence jones proteins in urine Anaemia - from overcrowding of bone marrow with monoclonal plasma cells Bone pain - Lytic lesions of bone
A Bence Jones protein is a monoclonal globulin protein or immunoglobulin light chain found in the urine,
Also freq. infection due to production of ‘useless’ malignant clone - immune paresis
Why is ESR elevated in multiple myeloma
Rouleaux formation in multiple myeloma
- ESR: measures the rate of fall of erythrocytes through plasma
- Rises if protein constituents of plasma increase or change
- Increases attractant charge
- Causes erythrocytes to clump together
- Clumped erythrocytes fall more quickly through plasma
Dengue also causes rouleaux formation
Investigations for ?MM
- Igs and electrophoretic strip, Urinary BJP, skeletal survey
Management of multiple myeloma
- Refer to haematologist for specialist management
- TX: corticosteroids, thalidomide, cyclophosphamide
- Usually 3-5yr survival.
Relationship with RA and pregnancy
- Post-partum presentation frequently described - possibly related to changes in Th cell profiles during/after pregnancy; Th2 cells tend to dominate during pregnancy with switch back to Th1 postpartum
- And as we discussed in the allergy lecture, Th1 is generally pro-inflammatory.
Rheumatoid arthritis - genetic predisposition
- HLA DR
- HLA DR4 present in 60-70% patients cf 20-35% controls (caucasian)
- Only specific DR4 subtypes, ie Dw4, Dw14, Dw15, are RA associated
- HLA DR1 also predisposes to RA
- Predisposing HLA class II molecules share common sequence at positions 70-74, an area predicted to lie within the alpha helix forming the wall of the peptide-binding groove
- Peptide presentation by disease associated HLA class II molecules may be involved in disease pathogenesis
- PAD type 2 and 4
- Peptidylarginine deiminase polymorphisms increase citrullination of proteins
- Suggests increased load of citrullinated proteins may increase likelihood of developing rheumatoid arthritis. Note the loss of B cell tolerance to citrullinated proteins in patients who develop rheumatoid arthritis
- PTPN 22
- Protein tyrosine phosphatase non-receptor 22 is a lymphocyte specific tyrosine phosphatase which suppresses T cell activation. 1858T allele increases susceptibility to rheumatoid arthritis, SLE, type 1 diabetes
- Suggests T cell activation is involved in pathogenesis of rheumatoid arthritis
Before starting a RA pt on biologics - what needs to be considered
- Consider risk of infection especially prior to use of ‘biologic’ agents
- Screen for exposure to TB using CXR and TB ELISPOT
- Screen for exposure to Hepatitis B
- Screen for exposure to Hepatitis C
- Consider possibility of HIV infection
- Prior history of septic arthritis/infected joint prosthesis
- Educate patient to stop drug and seek advice if acute infection
- Consider need for vaccinations
- Consider risk of malignancy
- Prior history of malignancy
- Advise re sun exposure/skin protection
Biologics in RA
- TNFa antagonist. Inhibits downstream events in inflammation. (etanercept, adalimumab)
- Rituximab. Antibody specific for CD20. Depletes B cells (not plasma cells).
- Tocilizumab. Antibody specific for IL-6 receptor – widespread effects
- Disruption of T cell function e.g. abatacept. Infrequent use if severe active RA that failed all three above. Abatacept. CTLA-4 – Ig fusion protein. Binds to ligands of CD28 (CD80 and CD86) and thereby inhibits T cell activation.
new (2018) oral drug for RA
- Oral biologics - tofacitinib, baricitnib (data suggest just as good as conventional DMARDs)
JAK inhibitors
What type of hypersensitivity reaction - serum sickness
Type 3 because it forms antibody-penicillin complexes, vasculitis, renal
What is rheumatoid factor
IgM antibody against Fc potion of IgG
Polymorphisms in peptide arginine deaminase (PADI) enzymes are associated with which disease
Rheumatoid arthritis
Transplant drugs
- Steroids
- Cyclosporin
- Tacrolimus
- Sirolimus
- OKT3
- IL-2 receptor antibody
- Anti-lymphocyte antibody
45M undergoes heart transplant. 72hours after, pt shows signs of organ rejection which is resistance to steroids. A mouse monoclonal antibody is administered to save the transplant
OKT3
Mouse monoclonal antibody targeting the human CD3, used to treat rejection episodes. The antibody efficiently clears T cells from the recipient’s circulation. T cell is the major mediator of acute organ rejection
CAUTION: may cause anaphylaxis due to murine protein stimulation immune system → potentially cytokine storm and death
Autoimmune antibodies
- Anti-smooth muscle
- p-ANCA
- c-ANCA
- Anti-Jo1
- anti-CCP
- Anti-centromere
- Anti-topoisomerase
- Anti-dsDNA
- Anti-parietal cell
- anti-TSH
45F with proximal myopathy. Rash surrounding both eyes. High resolution CT shows pulmonary fibrosis
Dermatomyositis
- Anti-Jo1
Helitrope rash around the eyes
Gottron’s papules
Non-nasolabial sparing malar rash (sparing think SLE)
Presence of anti-Jo1 typically suggest interstitial pulmonary involvement with raised ESR and raised CK levels
Assoc with SLE and scleroderma
Autoimmune antibodies
- Anti-smooth muscle
- p-ANCA
- c-ANCA
- Anti-Jo1
- anti-CCP
- Anti-centromere
- Anti-topoisomerase
- Anti-dsDNA
- Anti-parietal cell
- anti-TSH
43M with planes of fingers especially after cold weather + recent onset of difficulty in swallowing
- Anti-centromere
Limited systemic scleroderma CREST syndrome _calcinosis _raynauds _ oesophageal dysmotility _ sclerodactylyl _ Telangiectasia
Anti-topoisomerase is for diffuse systemic scleroderma
- involvement of kidneys, heart and lungs (pulmonary fibrosis)
Autoimmune antibodies
- Anti-mitochondrial muscle
- p-ANCA
- c-ANCA
- Anti-Jo1
- anti-CCP
- Anti-centromere
- Anti-topoisomerase
- Anti-dsDNA
- Anti-parietal cell
- anti-TSH
52M referred to gastro with itchy skin and malaise. Also bruising on arms and leg
- anti-mitochondrial
PBC!!!!
itching due to pruritis (increased bile acid in circulation)
Brusing due to poor absorption of fat soluble vitamins including Vit K, but also D - osteomalacia, A - blindness)
Dry eyes, dry mouth + joint pain
Diagnosis?
What other Sx
How to diagnose
Sjogren’s
Other Sx - Schirmer’s test for dry eyes, parotid swelling
Blood test show raised ESR and mild anaemia
Also ANA+
Diagnostic with salivary gland biopsy showing infiltrate of T and B cells, CD4+ T cell most prominent
Autoimmune antibodies
- Anti-mitochondrial muscle
- p-ANCA
- c-ANCA
- Anti-Jo1
- anti-CCP
- Anti-centromere
- Anti-topoisomerase
- Anti-dsDNA
- Anti-parietal cell
- anti-TSH
saddle shaped nose, frequent nose bleeds and haempytsis
- c-ANCA - GPA/Wegeners
Granulomatosus with polyangiitis
Saddle nose deformity due to perforated septum
Lungs (pulmonary haemorrhage)
Kidneys (glomerulonephritis)
Anti-ribonucleoprotein
Associated with mixed connective tissue disease
35F presents toGP with blurry vision and weakness in legs. CSF show oligoclonal bands of IgG on electrophoresis
Diagnosis?
What is the antigen?
Myelin basic protein are implicated in pathogenesis of multiple sclerosis.
MS is a demyelinating disease associate with antigenic stimulation of CD4+ T cells which activates CD8+ cytotoxic T cell directed against oliogdendrocyte proteins
Other clinics features
- optic neuritis
- urinary/bowel incontinence
- weakness of arm/legs
- dysphagia
34M known IVDU presents with 1 week history of fever, fatigue and abdo pain + joint pain. Angiogram reveals multiple aneurysm
- Stony fruit
- HBsAg
- Myelin basic protein
- Rhesus antigens
- Peanuts
- Anti-Serum
- Synovial membrane antigens
- Poison ivy
- HBsAg
Pt has polyarteritis nodosa (PAN) associated with pANCA. HepA is associated with PAN
Immune complexes deposited within vessels leading to fibrosis and vessel wall weakening → aneurysm
Corticosteroids and cytotoxic agents required to control disease progression
Anti-serum disease is when patient becomes sick after non-human nail source f serum is injected IV resulting in immune complex hypersensitivity type 3
45M with SLE presents to GP with nosebleed and gum bleeding when he brushes teeth. BT show v low platelet count
- Stony fruit
- HBsAg
- Myelin basic protein
- Rhesus antigens
- Glycoprotein IIb,IIIa
- Anti-Serum
- Synovial membrane antigens
- Poison ivy
- Glycoprotein IIb,IIIa
Pt has autoimmune ITP! IgG directed at platelets make them more susceptible to destruction and hence thrombocytopenia and bleeding
Secondary causes include SLE and antiphospholipid syndrome
39M MSM with PCP. What test to confirm underlying diagnosis?
- Histocompatibility
- Immunofluoresence
- Latex fixation
- Patch test
- Skin prick test
- Western blot
- DAT
- Western blot
Dude has HIV
Kveim test
Sarcoidosis
Not done in UK. Sample of spleen from known sarcoid injected into patient. Presence of non-caseating granule formation on biopsy of site 4-6 weeks after = pt has sarcoid
5 year old boy with purpura on legs and buttock, joint pain and abdo pain. Mother states child has suffered from sore throat approx 1 week before. Doctor like to perform an investigation to confirm diagnosis
- Histocompatibility
- Immunofluoresence
- Latex fixation
- Patch test
- Skin prick test
- Western blot
- DAT
- Immunofluoresence
Testing for anti-IgA antibody in HSP
Complement tests CD50 and AP50. What does each test
how does RA, SLE, membraoproliferative glomerulonpehritis affect complement levels?
CH50 is a marker for the classical complement activating pathway. AP50 is for the alternative pathway
Complements are also acute phase proteins. hence when there is chronic inflammation e.g .RA, there is increase in CH50
SLE there is complement consumption aka deficieny in C3 and C4, hence LOW C3 and C4 are markers of SLE activity
In membranoproliferative glomerulonephritis, there is nephritic factors (which are IgG against C3). Hence they will also have low C3. but v SLE, they have normal C4
if there is reduced AP50, means C3, B, D or P factors must be low. This predisposes pt to encapsulated bacteria
C1 inhibitor deficiency
hereditary angioedema, characterised by facial swelling
may lead to airway compromise and respiratory distress
DiGeorge CATCH 22
Cardiac abnormalities atresia Oesophageal Thymic hypoplasia Cleft lip HypoCa 22q11.2 mutation
what is the AIDS defining illness in HIV?
Candidiasis of the esophagus, bronchi, trachea, or lungs [(but NOT the mouth (thrush)]
Cervical cancer, invasive
Coccidioidomycosis, disseminated or extrapulmonary
Cryptococcosis, extrapulmonary
Cryptosporidiosis, chronic intestinal (greater than one month’s duration)
Cytomegalovirus disease (other than liver, spleen, or nodes)
Cytomegalovirus retinitis (with loss of vision)
Encephalopathy, HIV related
Herpes simplex: chronic ulcer(s) (more than 1 month in duration); or bronchitis, pneumonitis, or esophagitis
Histoplasmosis, disseminated or extrapulmonary
Isosporiasis, chronic intestinal (more than 1 month in duration)
Kaposi sarcoma
Lymphoma, Burkitt’s (or equivalent term)
Lymphoma, immunoblastic (or equivalent term)
Lymphoma, primary, of brain
Mycobacterium avium complex or M kansasii, disseminated or extrapulmonary
Mycobacterium tuberculosis, any site (pulmonary or extrapulmonary)
Mycobacterium, other species or unidentified species, disseminated or extrapulmonary
Pneumocystis jiroveci pneumonia
Pneumonia, recurrent
Progressive multifocal leukoencephalopathy
Salmonella septicemia, recurrent
Toxoplasmosis of brain
Wasting syndrome due to HIV
CD4 <200cells/ul
34F presents with itchy and desquamating, erythematous rash on the wrist approx 3 days after wearing new bracelet. which cytokine is first to be released during the initial exposure?
- IL10
- IFNy
- IL2
- TNFa
- IL12
- IL12
This is a Type 4 hypersensitivity reaction - long lag time, contact dermatitis
During first encounter, APC such as macrophage engulf allergen and presents to CD4. CD4 and macrophage communication to release IL12
During second exposure, the memory CD4 Th1 from first encounter now release IFNy, IL2 nad IL3 activating macrophages to release TNFa which causes the symptoms
IL10 is produced by Th2 cells which inhibits Th1 cells
56F with blurry vision and bilateral weakness. Vision worse after bath. what is most likely target in this disease process?
- pancreatic b-cell
- nickel
- proteolipid protein
- synovial membrnae
- tuberculin
- proteolipid protein
this woman has MS. MS also against myelin basic protein
pancreatic b-cell is for T1DM
nickel for contact dermatitis
synovial mmebrane protein is for RA
tuberculin for TB
How does HIV kill CD4 T cells
- Infected CD4 killed by CD8
- budding of HIV from CD4 causes rupture
- infected CD4 may fuse with uninfected CD4 to form syncytia giant cells thta ballooon and die
HIV and macrophages
HIV engulfed by macrophgae for APC are not destoryed
macrophages are also replicating reservoirs. Macrophage can enter BBB and this is how HIV can cross BBB
ANA staining patterns for the following conditions
- SLE
- Sjogrens
- Dermatomyositis
- mixed connective tissue disease
- drug induced SLE
- systemic sclerosis
SLE - speckled, anti-Smith
SLE - peripheral, anti-dsDNA
Sjogren - speckled, anti-Ro
Dermatomyositic - speckled, anti-Jo1
Mixed connective tissue disease - speckled, anti-RNP
Drug induced SLE - homogenous, anti-histone
Systemic sclerosis - nucleolar pattern, anti-RNA polymerase `
Autoimmun hepatitis autoantibodies type 1 v type 2
Type 1 - anti-smooth muscle and anti-nuclear
Type 2 - anti-liver kidney microsomal
Type 2 is more common in children (presents earlier) and poor steroid response type 1 is diagnosed aged 10 and up, good response to steroids
Dx caused by autoantibodies against
- Ganglioside LM1
- Ganglioside GM1
- Hu
- Myelin-associated glycoprotein
- Purkingje cells
- GBS
- ALS
- hu is part of peripheral nerves (PNS dx)
- MS
- CNS
GBS v ALS
- GBS symmetrical inflammatory polyneuropathy that begin sin the legs and ascends, finally affecting the muscles of respiratory
- ALS (amyotrophic lateral sclerorsis) subtype of motor neurone disease characterized by loss of neurons in the motor cortex as well as anterior horn of the spinal cord, therefore associated with upper rand lower motor neuron signs
35F referred to ophthalmologist after seeing floaters in right eye and lost of accommodation. 3 weeks ago, she had trauma to her left eye. Steroids were given to prevent potential loss of vision
- Keratoconjunctivitis sicca
- Sympathetic opthalmia
- Uveitis
- Keratitis
- Scleritis
- Sympathetic opthalmia
Her recent trauma to the eye has caused break in immuno privillege. eyes are immunoprivilleged sites.
Presentation of photoreceptor antigento immune cells now have caused the body’s own immune cells to target the eyes which may lead to blindness
- keratoconjunctivitis sicca is related to Sjogren. Tested by Schirmer’s test
Clinical diagnostic criteria for anaphylaxis (3 ways)
- Known allergen + low BP
- Likely allergen + >2 of following:
- skin signs
- resp signs
- low BP
- GI signs e.g. crampy abdo pain, vomiting - No/unknown allergen + acute onset of skin signs (urticaria, angio-oedema) + 1 of the following:
- respiratory signs
- decreased BP, collapse, syncope, incontinence
A 26 year old male who has been suffering from ‘flu-like’ symptoms with fever presents to the GP after developing skin rash in the last few days
vs
A 35 year old woman presents with persistent itchy wheels for the last 2 months. She noticed that when this is at its worst, she also has a fever and feels generally unwell. After an acute attack, she has bruising and post-inflammatory residual pigmentation at the site of the itching.
Top 26M is acute urticaria
Bottome 35F is urticaria vasculitis
Acute urticaria is defined being present for less than 6 weeks, whereas chronic urticaria persists
for more than 6 weeks. In both cases the urticarial rash is intermittent, comes and goes and normally
persists in a single site for less than 24 hours.
Urticarial rashes that last more than 24 hours in a single site, resolve with bruising or skin depigmentation
may raise the possibility of an underlying vasculitis. In this instance a skin biopsy of the urticarial
lesion is useful to confirm/repute presence of a vasculitis.
A 55 year old man with history of angina was advised to take a tablet before a long flight. After taking the pill, he suddenly finds that he has difficulty breathing, feels nauseous and is itching.
All Answer Choices A. C1 inhibitor deficiency B. Extrinsic allergic alveolitis C. Allergic asthma D. Urticarial vasculitis E. Idiopathic angioedema F. IgE mediated anaphylaxis G. Coeliac disease H. Chronic urticaria I. Panic attack J. Acute urticaria K. Mast cell degranulation
Correct K. Mast cell degranulation
NOT F. IgE mediated anaphylaxis
Because the tablet for angina that he took was aspirin. And aspirin related allergies are mast cell mediated not IgE
A 24 year old medical student develops worsening swelling of the hands and feet and abdominal pain before her final year medical exams. She says that similar milder episodes have occurred preciously.
C1 inhibitor deficiency or panic attack?
Correct A. C1 inhibitor deficiency
this is not panic attack because there is usually no ACTUAL SWELLING in panic attacks
CI inhibitor def = classically ANGIO-OEDEMA + itch + abdo pain (just like allergies BUT there is no IMMUNOLOGICAL BASIS!
A 35 year old woman presents with a two day history of a red itchy skin rash which started soon after her first scuba-diving lesson. She is otherwise well.
All Answer Choices A. Contact hypersensitivity B. Allergic bronchopulmonary aspergillosis C. Anaphylaxis D. Allergic rhinitis E. Hereditary angioedema F. Allergic asthma G. Acute angioedema H. Acute urticaria I. Allergic conjunctivitis J. Chronic urticaria
Correct H. Acute urticaria
THIS IS NOT CONTACT HYPERSENSTIVITY!!
because the rash appeared too quickly after her scuba diving. This is LATEX allergy which is acute urticaria!
For contact derm, you need DAYS to develop becasue it is T cell mediated and you usually NEED an sensitisation event first
Tx with PO antihistamines
A 22 year old woman presents with an intermittently itchy and desquamating skin rash on her abdomen which is unresponsive to antihistamines
A. Contact hypersensitivity B. Allergic bronchopulmonary aspergillosis C. Anaphylaxis D. Allergic rhinitis E. Hereditary angioedema F. Allergic asthma G. Acute angioedema H. Acute urticaria I. Allergic conjunctivitis J. Chronic urticaria
Correct A. Contact hypersensitivity
THIS IS NOT CHRONIC URTICARIA because this is NOT histamine driven because it was UNRESPONSIVE TO HISTAMINE!
urticaria = histamine, mast cells
contact hypersensitivity is T cell mediated hence NOT HISTAMINE
This 45 year old woman presents to A&E with tongue swelling and acute respiratory tract obstruction. She has longstanding hypertension and received a renal transplant two years previously. She has no history of allergic disease. On examination her blood pressure is stable, and examination of her lung fields reveal normal breath sounds. Her current medication includes cyclosporine, azathioprine, captopril and nifedipine.
What is the cause of her symptoms?
SPOT THE ACEi
IN ALL ALLERGY QUESTIONS, SPOT THE ACEi and stop it.
Intramuscular adrenalin should be used in patients with severe local angioedema with secondary acute respiratory tract obstruction. However this is not always effective in ACE inhibitor-induced angioedema, and some patients will require intubation. Always stop the causative agent!
MHC associated with Th1 and Th2 cells
Major histocompatability complex class 2
MHC associated with cytotoxic T cells
Major histocompatability complex class 1
Which complement factor is an important chemotaxic agent?
C3a
C3 is cleaved into C3a and C3b. C3a is chemotaxis and C3b is the activates C5-C9.
