Immuno Flashcards
SUMMARY CARD:
What are the 4 main types of cells in the innate immune system?
- Granulocytes: neutrophils, eosinophils, basophils
- Monocytes (in blood) + macrophages (same as monocyte but found in tissue) –> APCs to T-cells
NOTE: macrophage named differently based on where it is found e.g. liver (Kupffer), kidney (mesangial), spleen (sinusoidal lining), bone (osteoclast), lung (alveolar macrophage), neural (microglia), connective (histiocyte), skin (langerhans) - Natural killer (NK) / cytotoxic cells: kill ‘altered’ self cells e.g. those that are malignant or
infected with a virus
- Dendritic cells: reside in peripheral tissues and modulate the innate and adaptive immune system
SUMMARY CARD:
How does the innate pathway normally function?
Phagocyte development; migration to infection; non vs oxidative methods
- Phagocytes produced in
bone marrow
–> released into blood - Types of phagocytes: neutrophils (die afterwards) + macrophages (signal to T-cells after) = phagocytosis; dendritic cells mediate the transition between innate and addaptive immune cells
- Endothelial cells in blood vessels release / express
adhesion molecules
e.g. ICAM-1 (make the blood vessel wall stickier) - Infection releases cytokines and chemokines, which attracts the phagocytes. Adhesion molecules allow the phagocytes to stick to the blood vessel wall + access the microorganisms
- Phagocytosis occurs (engulf the pathogen)
- Pathogen is killed via oxidative and non-oxidative methods
-
Oxidative
: Firstly, reduction: O2 –NADPH oxidase–> H2O2; then H2O2 + Cl2 –myeloperoxidase –> 2HClO (hydrocholorous acid) -
Non-oxidative
: lysozymes - As phagocytosis can be done by neutrophils OR macrophages:
- Neutrophils: Phagocytosis depletes glycogen reserve –> results in CELL DEATH and therefore residual enzymes liquify surrounding tissue (PUS!!)
- Macrophages: become activated + release cytokines to interact with T-cells
SUMMARY CARD:
What deficiencies in the phagocyte pathway can lead to which disorders?
Clue: production, maturation, migration, oxidative killing
Primary immune deficiences in PHAGOCYTES can lead to:
1. Failure to produce neutrophils:
-
Reticular dysgenesis
(auto reccessive = MOST SEVERE SCID) –> mutation in adenylate Kinase 2 (AK2) = NO lymphoid or myeloid cells(LOW B and T cells)
-
Kostmann Syndrome
(autosomal recessive = severe congenital neutropenia) –> mutation in HCLS1-associated protein X-1 (HAX-1) = LOW neutrophils (and as neutrophils are responsible for pus formation,NO PUS!
) -
Cyclical neutropenia
(autosomal dominant) –> mutation in Neutrophil Elastase (ELA-2) = fluctuating neutropenia every 4-6 weeks
2. Failure of phagocyte migration:
-
Leucocyte adhesion deficiency
(autosomal recessive) –> mutation in CD18 Beta-2 integrin subunit = LFA-1 on neutrophils cannot bind to adhesion molecule ICAM-1 so cannot migrate to infection site =very high neutrophil count
and NO PUS
3. Failure of oxidative killing:
-
Chronic granulomatous disease
(X-linked recessive / auto recessive) –> defective NADPH oxidase = lack of ROS = normal cell counts as deficiency is to do with the enzyme, not the granulocytes
4. Deficiency of cytokines:
-
Interferon-gamma/IL-12 deficiency
= deficiency in IFN-y, IL-12 and their receptors = ↑ susceptibility to mycobaterial infections (e.g. TB, salmonella) AND normal neutrophil count
SUMMARY:
What is the normal IL-12 and IFN-gamma pathways?
stimulates oxidative pathways!
- Infected macrophages produce IL-12
- IL-12 induces T-cells to secrete IFN-y
- IFN-y feeds back to macrophages & neutrophils
- Stimulates the production of TNF
- Activates NADPH oxidase = stimulation of the oxidative pathway(s)
DISEASE:
SEVERE sepsis few days after birth
Usually do not survive past 1 year in infancy
Sensorineural deafness
LOW T and B cells
- Diagnosis?
- Mutation?
- Inheritance pattern?
- Management?
Most severe phagocyte deficiency
reticular dysgenesis
- adenylate kinase 2 (AK-2)
- auto recessive
- fatal in early life unless corrected with bone marrow transplant
NOTE: AK2 is responsible for devloping certain structures in the ear –> which is why it presents with sensorineural deafness!
DISEASE:
ISOLATED low neutrophils
NO PUS formation
- Diagnosis?
- Mutation?
- Inheritance pattern?
- Management?
-
Kostamann Syndrome
(severe congenital neutropenia) - HCLS1-associated protein X-1 (HAX-1)
- auto recessive
- granulocyte-colony stimulating factor (G-CSF)
DISEASE:
Fluctuating neutropenia every 4-6 weeks
e.g. X pt is found to have low neutrophils. 6 weeks later, they are back to normal.
- Diagnosis?
- Mutation?
- Inheritance pattern?
- Management?
cyclic neutropenia
- neutrophil elastase = enzyme (ELA-2 = gene)
- auto dom
- granulocyte-colony stimulating factor (G-CSF)
DISEASE:
Delayed umbilical cord separation
Absence of pus formation
VERY HIGH neutrophil counts in blood
- Diagnosis?
- Mutation?
- Inheritance pattern?
- Management?
leukocyte adhesion deficiency
- CD18 B2 integrin subunit
- auto recessive
- neutrophils are deficienct in adhesion receptors therefore are useless –> Mx with haematopoietic stem cell transplant
DISEASE:
Increases susceptibilibity to bacterial infections: PLACESS (pseudomonas, listeria, aspergillus, candida, E coli, staph, serratia)
CHRONIC INFLAMMATION
Non-caseating granuloma formation
Lymphadenopathy, hepatosplenomegaly, recurrent skin / fungal infections
NORMAL neutrophil / WBC count
- Diagnosis?
- Mutation?
- Inheritance pattern?
- Investigations?
- Management?
(failure of oxidative killing)
chronic granulomatous disease
- mutation in ENZYME NADPH oxidase (so normal WCC)
- X-linked recessive or autosomal recessive
- abnormal
dihydrorhodamine
= no flourescence (normal: flourescence); abnormal nitroblue tetrozolium (NBT
) test = remains yellow (normal: colour change yellow –> blue) - interferon-gamma therapy
DISEASE:
Increased susceptibility to atypical mycobacterial
infections e.g. TB, salmonella
Inability to form granulomas
NORMAL neutrophil count
- Diagnosis?
- Mutation?
Interferon-gamma/IL-12 deficiency
- IFN-y, IL-12 and their receptors
SUMMARY CARD:
What is the purpose of natural killer (cytotoxic) T-cells?
How do they kill cells?
- Present within the blood + migrate to inflamed tissue
- Typically, they express inhibitory receptors for self-HLA molecules to avoid accidental inappropriate action against self cells
- HOWEVER, they express a range of activating receptors that allow it to kill ‘altered’ self cells e.g. those that are malignant or
infected with a virus
(as these lack the inhibitory signals of normal self antigens) –> so deficiency in this = ↑risk of viral infection
2 main mechanisms of killing ‘altered’ self cells:
1. Perforin (pokes holes in membranes) + granzymes
2. Fas ligand expression –> triggers apoptosis
DISEASE:
↑risk of viral infection e.g. HERPES
Typical SBA: child with severe chickenpox or disseminated CMV
Which 2 NK deficiencies could this be and how is it managed?
-
Classical NK deficiency =
ABSENCE
of NK cells in peripheral blood -
Functional NK deficiency = NORMAL levels of NK cells in blood BUT
non-functional
Mx for both = prophylactic antivirals; IFN-alpha to stimulate NK cells and if severe –> HSCT
SUMMARY CARD:
What is the complement cascade and how does it normally function?
How is the complement cascade activated?
Complement cascade = sequence of reactions that complement/enhance the rest of the immune system
They are inactive proteins produced by the liver + exist in the circulation
Triggers e.g. infection = series of enzymes cleave the proteins and initiate a cascade of reactions
This leads to the END POINT: membrane attack complex (MAC
) –> attacks pathogen cell membrane (pokes holes)
ALSO: fragments released during cascade leads to:
- ↑ vascular permeability –> immune cells can reach the infected tissue more easily
- Activated phagocytes = ↑ phagocytosis
- Opsonise (make pathogen more susceptible to phagocytosis e.g. by marking it for destruction) pathogens + immune complexes
- Promote mast cell + basophil degranulation
Activation of complement cascade:
Classical pathway: C1, C2, C4
- Requires a functioning immune system as they are activated via an antigen-antibody (Ag-Ab) complex
- Conformational change in Ag-Ab complex exposes binding site for C1 activation –> the binding initiates cascade
Alternative pathway: C3
- Activated by pathogens of apoptotic tissue
Mannose-binding lectin: C4, C2
- Activated by serum lectin binding sugars (which may be found on bacterial cell walls or yeast cells)
The combination of C4b+C2a forms C3 convertase, which converts C3 to C3a (inflammation) and C3b (opsonisation)
Afterwards, this all feeds into a final common pathway composed of C5 convertase and C5-C9 –> this eventually forms the end product: MEMBRANE ATTACK COMPLEX (MAC)
NOTE: a cleaved complement divides into a (smaller) and b (bigger) fragments e.g. C3a + C3b
SUMMARY CARD:
What deficiencies in the complement cascade can lead to which disorders?
1. Classical
pathway deficiencies:
- Deficiency in
C2
(auto recessive) = most common –>↑ SLE in childhood + severe skin disease
NOTE: normally classical pathway is activated by Ag-Ab complexes and it triggers phagocyte mediated clearance of these immune complexes, therefore lack of this = immune complex deposited in organs/joints (SLE)
2. MBL
pathway deficiencies:
MBL deficiency (auto recessive) on its own is not an issue (no immunodeficiency), HOWEVER, paired with another immune impairment e.g. HIV, prematurity, chemotherapy, antibody deficiency etc. –> can cause immunodeficiency + ↑infection risk
3. C3
deficiency:
Severe susceptibility to ENCAPSULATED bacterial
infections
4. Secondary
C3
deficiency:
-
C3 deficiency w/ nephritic factors
= nephritic factors stabilise C3 convertase which results in ↑activation + consumption of C3 –> associated with membranoproliferative glomerulonephritis + partial lipodystrophy (abnormal fat distribution) –> LOW C3, NORMAL C4 -
SLE
= production of immune complexes results in consumption of C3 + C4 –> LOW C3 and LOW C4
5. Alternative pathway deficiency:
- Properdin deficiency = RARE: properdin is a protein in the alternative pathway that typically stabilises C3 convertase –> absence = recurrent
encapsulated
bacterial infection esp. Neisseria - Other alternative pathway deficiencies = factor B or factor D
6. Terminal pathway deficiency (C5-C9):
Any defect results in inability to form membrane attack complex (MAC) –> recurrent encapsulated
bacterial infection esp. recurrent meningococcal disease + FAMILY HISTORY
NOTE: C9 deficiency often asymptomatic
NOTE: NHS for encapsulated bacteria = Neisseria meningitis; Haemophilus influenzae; Streptococcus pneumoniae
DISEASE:
How do you differentiate between complement deficiency causing SLE and SLE causing complement deficiency?
Most common complement deficiency to cause SLE = C2 deficiency –> therefore, NORMAL levels of C3 + C4
HOWEVER, if pt has SLE, lupus causes the production and deposition of immune complexes which consumes and consequently depletes C3/C4 levels –> so LOW levels of C3 + C4
SUMMARY CARD:
How can you remember the encapsulated bacteria?
NHSN
-eisseria meningitisH
-aemophillus influenzaeS
-treptococcus pneumoniae
DISEASE:
What are the investigations to test for complement pathway deficiencies?
classical vs alternative?
Measure C3 + C4 levels:
- LOW C3 + LOW C4 = active SLE
- LOW C3, NORMAL C4 = C3 deficiency with nephritic factors (membranoproliferative glomerulonephritis)
- NORMAL C3 + NORMAL C4 but SLE = C2 deficiency
C
H50:
- Marker of
c
lassical pathway (+ve = normal; -ve/absent = abnormal)
A
P50:
- Marker of
a
lternative pathway (+ve = normal; -ve/absent = abnormal)
NOTE: both CH50 + AP50 are markers of C3 to C5-C9
DISEASE:
Recurrent neisseria / Hib / strep pneumoniae infections
- Diagnosis?
- Management?
- Presenting with recurrent NHS (
encapsulated
bacterial infections) –>complement deficiency
- Mx = vaccinations against NHS, prophylactic abx, treating infections aggressively,
screen family members
(esp w/ C5-C9 deficiency)
DISEASE:
SLE in childhood
vasculitic rash / severe skin disease
glomerulonephritis
arthritis
What is the diagnosis?
What is absent on Ix?
Classical pathway deficiency –> C2
deficiency = most common
Absent CH50
DISEASE:
Aymptomatic on its own
Immunodeficient when paired with prematurity / HIV/ chemo therapy –> Pt has recurrent Neisseria infection
What is the diagnosis?
MBL (mannose-binding lectin) complement pathway deficiency
DISEASE:
Membranoproliferative glomerulonephritis + partial lipodystrophy (abnormal fat distribution)
What is the diagnosis?
C3 deficiency with nephritic factors
–> nephritic factors cause consumption of C3
Therefore LOW C3, normal C4
Recurrent Nesseria infection
What is the diagnosis?
What is absent on Ix?
Alternative complement pathway deficiency
- Properdin deficiency = RARE: properdin is a protein in the alternative pathway that typically stabilises C3 convertase –> absence = recurrent
encapsulated
bacterial infection esp. Neisseria - Other alternative pathway deficiencies = factor B or factor D
Absent AP50
DISEASE:
Recurrent meningococcal disease (e.g. NHS) + FAMILY HISTORY
What is the diagnosis?
Terminal complement pathway deficiency (C5-C9 deficiency
)
NOTE: C9 deficiency often asymptomatic
SUMMARY CARD:
Development of the T-cell adaptive immune response and how does it normally function?
- T-cells are produced in the bone marrow + undergo
maturation in the thymus
-
Central tolerance:
HLA matching
in the thymus –> those with a too low OR too high affinity for HLA are not selected for maturation (die as immature T-cells) as they would have inadequate reactivity - Only the INTERMEDIATE affinity for HLA are selected for during maturation (~10% of the immature of T cells) –> they can have an affinity to class I or II
- Those with an affinity for
class I
develop into CD8+ T-cells (NK) –> important for virus infected cells + tumours:
- Kill cells via perforin (holes in membrane) + granzyme
- Can also kill cells via fas ligand expression
- Those with an affinity for
class II
develop into CD4+ T-cells:
- Help with the B-cell response
- Help promote CD8+ (NK) cell action
SUMMARY CARD:
What deficiencies in the T-cell pathway can lead to which disorders?
failure of: production, maturation, activation
1. Failure of lymphoid cell production
-
Reticular dysgenesis
(auto reccessive = MOST SEVERE SCID) –> mutation in adenylate Kinase 2 (AK2) = NO lymphoid or myeloid cells (AKA affects the innate AND immune response) =(LOW B and T cells)
-
Severe combined immunodeficiency (SCID)
–> 20 possible pathways = unwell by 3 months of age as no longer protected by the maternal IgG that crossed the placenta e.g. failure to thrive, persistent diarrhoea, poorly developed thymus, FHx of early infant death -
X-linked SCID
= most common (45% of all SCID) –> mutation in gamma chain of IL-2 receptor on Chromosome Xq13.1 results in poor cytokine response = early arrest of T-cells and NK cell development + production of IMMATURE B-cells =low/absent T cells & NK cells BUT normal (immature) B-cell count
-
ADA deficiency
–> mutation of adenosine diaminase (ADA), an enzyme required for lymphocyte metabolism, therefore deficiency =low/absent T cells, NK cells & B-cells
NOTE: (definitive) Mx for above = HSCT as all are issues in the bone marrow
2. Failure of maturation/selection in the thymus
-
DiGeorge Syndrome
(22q11.2 deletion) –> smaller/absent thymus = lack of mature T-cells, which consequently reduces B-cell function (↓IgG) as T-cells normally activate B-cells to produce IgG = NORMAL B-cell count BUT low T-cell -
Bare lymphocyte syndrome (BLS) type I
–> defect in MHC class I = deficiency of CD8+ (NK) cells -
Bare lymphocyte syndrome (BLS) type II
–> defect in MHC class II = deficiency of CD4+ but normal CD8+ (NK) + B-cell count –> lack of CD4+ = lack of B-cell activation to produce IgG or IgA via class switching
3. Failure of T-cell activation and effector functions
-
Interferon-gamma/IL-12 deficiency
= deficiency in IFN-y, IL-12 and their receptors = ↑ susceptibility to mycobaterial infections (e.g. TB, salmonella) AND normal neutrophil count -
Hyper IgM syndrome
= failure to express CD40L on activated T-cells (normally CD40-ligand on T-cell causes B-cell differentiation from IgM to IgA/G/E) –> therefore absent IgA/G/E + ELEVATED IgM -
Wiskott-Aldrich Syndrome (WAS)
= mutation in Wiskott-Aldrich Syndrome Protein (WASP); Xp11.23 –> WASP stabilised T-cell APC interaction therefore mutation in this limits the primary response with IgM = low IgM BUT elevated IgA + IgE as pts present with eczema, thryombocytopenia, ↑ risk of autoimmune disorders and malignancy (lymphomas and leukaemias)
DISEASE:
Unwell by 3 months
of age with infections of all types
Failure to thrive
Persistent diarrhoea
Poorly developed thymus
FHx of early infant death
What is the diagnosis?
Severe combined immunodeficiency (SCID)
DISEASE:
Very low/ absent T cells and NK cell count
Normal B cell count
Sx of immunodeficiency in childhood e.g. failure to thrive, recurrent infections, persistent diarrhoea etc.
What is the diagnosis?
X-linked SCID
NOTE: normal B-cell count, but B-cells immature as IL2-receptor mutation = poor cytokine response –> early arrest of T + NK cells (low count) and no maturation if B-cells
Very low/ absent T cells and NK cell count
AND low B cell count
Sx of immunodeficiency in childhood e.g. failure to thrive, recurrent infections, persistent diarrhoea etc.
What is the diagnosis? (+ Mx?)
Adenosine Deaminase (ADA) deficiency
NOTE: ADA responsible for lymphocyte cell metabolism
Mx = PegADA or HSCT (definitive)
DISEASE:
Developmental defect of pharyngeal pouch
Small/absent thymus
Tetralogy of Fallot
Prominent forehead, wide-set eyes, and small chin
Cleft palate
Hypocalcaemia
Recurrent infections in childhood that get less frequent with age
What is the diagnosis & mutation? (+ Mx?)
DiGeorge Syndrome
Sx: CATCH-22
- C-ardiac abnormalities e.g. Tetralogy of Fallot
- A-bnormal facies (high forehead, low set ears)
- T-hymic hypoplasia
- C-left palate
- H-ypocalcaemia (lack of PTG = low Ca2+)
- 22 - 22q.11.2 (remember as 11x2=22)
- Homeostatic proliferation with age = frequency of infections reduce as immune function improves with age
Lack of mature T-cells but normal B-cell count
NOTE: normally T-cells activate B-cell differentiation to produce IgG, however, this is impaired = LOW IgG
Mx = thymic transplant
DISEASE:
LOW CD8+ (NK) cell count
Bare lymphocyte syndrome type I = mutation in class I = CD8+ deficiency
DISEASE:
Fhx of early infant death
Sclerosing cholangitisNormal B cells + IgM but low IgA and IgG
What is the diagnosis?
Bare lymphocyte syndrome (BLS) type II
= mutation in class II = CD4+ deficiency
NOTE: CD4+ normally promotes B-cell differentiation and class switching to produce IgA and IgG (therefore, normal B-cell + IgM BUT low IgA + IgG)
DISEASE:
TRIAD: eczema (raised IgE), thrombocytopenia (low platelet count), + recurrent bacterial infections
Easy bruising
↑ risk of autoimmune disorders and malignant lymphomas
What is the diagnosis + mutation? (+ levels of IgM / IgA / IgE)
Wiskott-Aldrich Syndrome (WAS)
= mutation in WAS-protein; Xp11.23
↑ IgE (eczema)
↑ IgA
↓ IgM
SUMMARY CARD:
Development of the B-cell adaptive immune response and how does it normally function?
- B-cell produced and matured in the bone marrow
-
Central tolerance:
HLA matching
in bone marrow –> those with affinity for self-HLA are not selected for maturation (die as immature B-cells) to avoid autoreactivity - ONLY those with NO recognition of self in bone marrow survive and mature!
- Initially formed B-cells produce IgM response, which is
T-CELL INDEPENDENT
-
Germinal centre reaction: dendritic cells prime CD4+ T-cells –> CD4+ help B-cell differentiation via CD40-ligand –> leads to B-cell proliferation + isotype
switching e.g. to IgA, IgG, IgE
SUMMARY CARD:
What deficiencies in the B-cell pathway can lead to which disorders?
1. Failure of B-cell production
-
Reticular dysgenesis
(auto reccessive = MOST SEVERE SCID) –> mutation in adenylate Kinase 2 (AK2) = NO lymphoid or myeloid cells (AKA affects the innate AND immune response) =(LOW B and T cells)
2. Failure of B-cell maturation
-
Bruton’s X-linked hypogammaglobulinemia
(X-linked, BTK gene): only affectsB
oys –> mutation in Bruton Tyrosine Kinase (BTK) = pre-B-cells cannot develop into mature B-cells, therefore absence of mature B-cells and no circulating Ig after ~3 months –> leads to recurrent infections during childhood + absent lymph nodes & tonsils
3. Failure of class-switching
-
Selective IgA deficiency
(most COMMON deficiency): unknown genetic component; many individuals asymptomatic, associated with recurrent GI/resp infections (~30%) as IgA present on mucosal surfaces, coeliac and SLE and/or anaphylaxis after blood transfusion (NOTE: so in IgA deficiency use anti-TTG IgG to test for coeliac instead) -
Hyper IgM syndrome
(X-linked recessive): mutation in CD40-ligand on T-cell (CD40L normally aids B-cell differentiation + class-switching) = elevated IgM and NO IgE/A/G –> boys esp. present with failure to thrive, recurrent bacterial infections, no germinal centre development within lymph nodes or spleen, etc. -
Common variable immune deficiency
= diagnosis of EXCLUSION (make sure B and T cells are normal first) AND >4 y/o–> LOW IgG, IgA and IgM = poor response to immunisation; recurrent bacterial infections with end-organ damage etc.
DISEASE:
Affects BOYS
Recurrent bacterial infections during childhood (after 3 months)
Absent/scanty lymph nodes + tonsilsFailure to respond to immunisations
;
Ix: NORMAL T cells, ABSENT B cells + Immunoglobulins
What is the diagnosis? (+ Mx?)
Bruton’s X-linked hypogamma globulinemia
(only affects b
oys as X-linked)
NOTE: pre-B cells cannot mature = lack of Ig
Mx = pooled human IG every 3 weeks
DISEASE:
Recurrent GI/resp infections
Coeliac / SLE
Anaphylaxis after blood transfusion (anti-IgA Abs)
What is the diagnosis?
IgA deficiency
= LOW IgA BUT normal IgM/IgG
Anti-IgA Abs mean pts have anaphylaxis if they get a blood transfusion
GI/resp infections more common because IgA protects mucosal surfaces
DISEASE:
First few days of life (typically in BOYS) –> pneumocystis jiroveci pneumonia infection
↑ risk of AI disease + malignancy
What is the diagnosis? (+ Mx?)
Hyper IgM Syndrome
Lack of CD40-ligand on T cell = lack of B-cell class switching –> Normal B and T cells, ↑ IgM (due to failure of isotype switching), ↓ IgA, IgG and IgE
Mx = IVIG
NOTE: Wiskott-Aldrich (WAS) is the opposite, ↑ IgA and IgE BUT ↓ IgM due to excessive class switching
DISEASE:
Normal T-cells and B-cells
LOW IgG, IgA and IgM
Poor response to immunisation
Recurrent bacterial infections with end-organ damage
GI and pulmonary disease e.g. bronchiectasis, ILD, IBD
AI disease e.g. RA, pernicious anaemia, thyroiditis
What is the diagnosis?
Clue: diagnosis of exclusion
Common variable immune deficiency
QUESTION:
Which Ig is required for effective immunisation?
Require IgG for effective immunisation
SUMMARY SLIDE:
What are some examples in the spectrum of autoinflammatory to autoimmmunity?
↑
|Rare monogenic autoinflammatory diseases
|Polygenic autoinflammatory diseases
|Mixed pattern disease
|Polygenic autoimmune diseases
|Rare monogenic autoimmune disease
↓
Autoinflammatory
= innate immune responseAutoimmune
= adaptive immune response
Mixed innate + adaptive = mixed
↑
|Rare monogenic autoinflammatory diseases: Familial mediterranean fever, Muckle Wells Syndrome
|Polygenic autoinflammatory diseases: Crohns disease, UC, osteoarthritis, GCA (PMR RF for this), Takayasu’s arteritis
|Mixed pattern disease: AS, psoriatic arthritis, Behcet’s
|Polygenic autoimmune diseases: RA, MG, pernicious anaemia, Graves’, SLE, primary biliary cirrhosis, ANCA associated vasculitis, Goodpasture’s disease
|Rare monogenic autoimmune disease: APS-1, APECED, ALPS, IPEX
↓
SUMMARY SLIDE:
Monogenic autoinflammatory disease
Guess the diagnosis and mutation (+/- Mx):
- Flare ups =
periods of intense fever lasting 2-4 days
, serositis (peritonitis, abdo pain, pleurisy, pericarditis and rash), AA amyloidosis (rare type of amyloidosis)
e.g. child with unexplained episodic fevers -
Sensorineural deafness
+ recurrent episodes of hives, athralgia, conjunctivitis, serositis, ascites (non-tender)
-
Familial mediterranean fever
(auto recessive)
- MEFV gene normally responsible for the protein pyrin-marenostrin, which helps control inflammation
-
Mutation in MEFV gene
= reduced pyrin-marenostrin (thus ↑ IL-1), therefore –> uncontrollable inflammation / pain / fever - Ix = Tel HaShomer Criteria (1 major or >1 minor criteria)
- Mx 1st line = colchicine (binds to tubules in neutrophils); 2nd line = Anakinra (IL1-receptor antagonist) or Etanercept (TNF-alpha inhibitor)
-
Muckle Wells Syndrome
(auto dominant)
- Mutation in
NLRP3 gene
= ↑ cryopyrin = ↑ IL1-beta = ↑ inflammation - Sensorineural hearing loss develops overtime due to chronic inflammation of the inner ear
- Mx = Anakinra (
IL1-receptor antagonist
)
SUMMARY CARD:
Monogenic autoimmune
Guess the diagnosis and mutation (+/- Mx):
-
Endocrine disease
–> hypoparathyroidism (most common) = hypocalcaemia, Addison’s, hypothyroidism, T1DM
Chronic mucocutaneous candidiasis, enteropathy (diarrhoea) + mild immune deficiency (recurrent infections) -
Endocrine disease
–> T1DM, hypothyroidism
Enteropathy (diarrhoea), eczema/dermatitis
REMEMBER 3Ds:diarrhoea, diabetes, dermatits
-
High lymphocyte count
Autoimmune cytopenias, lymphoma, splenomegaly, lymphadenopathy
-
Autoimmune polyendocrine syndrome type 1
(APS-1) or Autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy (APECED)
- Auto recessive condition resulting in abnormal tolerance (AKA autoreactive immune cells DON’T die)
- Mutation in auto-immune regulator protein (AIRE) –> leads to autoreactive T-cells in thymus = auto-reactive B-cells =
production of autoantibodies
-
Immune dysregulation, polyendocrinopathy, enteropathy X-linked
(IPEX) syndrome
- X-linked condition resulting in failure to regulate T-cell responses
- Mutation in FOXp3 transcription factor, a master protein regulator for the development T-regulatory cells
-
Failure to negatively regulate T-cell response = T-cell autoimmunity = B-cell autoimmunity =
production of autoantibodies
Autoimmune lymphoproliferative syndrome (ALPS)
- Mutation in FAS pathway (death/apoptosis pathway)
- Results in defect of lymphocyte apoptosis –>
failure of tolerance
- Thus: ↑ HIGH lymphoctye count + autoimmune cytopenias
DISEASE:
Polygenic autoinflammatory disease
Guess the diagnosis + mutation (+/- Mx)
-
Crampy abdominal pain, diarrhoea, mucosal ulcerations
'Cobblestone mucosa'
- skip lesions
Focal inflammation around crypts + granulomatas
- Crohn’s disease
- Mutation in NOD-2 or CARD-15 (menumonic: crap ass rectal disease)
- Normally, NOD2 is an intracellular microbial receptor that causes autophagy of dendritic cells when activated
- However, abnormal NOD2 = disordered degradation of immune cells –> inflammation
SUMMARY CARD
Which gene is associated with mixed pattern autoinflammatory + autoimmune conditions?
Guess the diagnosis:
- Enthesitis (achilles tendonitis, sacroilliitis), large joint arthritis,
low back pain
, joint stiffness relieved by exercise, acute iritis - Red, scaly patches, joint pain, dactylitis etc.
- episodes / flares of:
recurrent oral and genital ulcers
, uveitis, thrombophlebitis (vasculitis), painful joints
Seronegative arthropathies AKA HLA-B27
: Ankylosing spondylitis, psoriatic arthritis
- Ankylosing spondylitis - HLA-B27 association, highly heritable, associated with uveitis + UC
- Psoriatic arthritis - HLA-B27
- Behcet’s disease - HLA-B51
SUMMARY CARD:
How do these mutations cause polygenic autoimmune disease + what autoimmune conditions do they cause?
- PTPN22
- CTLA4
These are both genetic polymorphisms:
- PTNP22 codes for a protein tyrosine phosphatase –> important negative T-cell regulator. Mutation in this = development of
RA, SLE, T1DM
- CTLA4 is a is a protein receptor expressed by T-cells that transmits inhibitory signals to control T-cell activation (negative T-cell regulator). Mutation in this = development of
SLE, T1DM, autoimmune thyroid disease
SUMMARY CARD:
Polygenic autoimmune disease
Guess the diagnosis (type of hypersensitvity) + autoantibodies (+/- Mx)
- Hyperthyroidism, diffuse goitre, exopthalmos, pretibial myxoedema
- Hypothyroidism, diffuse goitre, associated with MALT lymphoma
- Polyuria/nocturia, polydipsia, weight loss OR abdo pain + raised ketones (metabolic acidosis)
- Macrocytic anaemia + ↑ megaloblasts (RBC precursor)
- Muscle weakness that worsens with movement; thymoma
- Muscle weakness improves with movement, NSCLC
- Glomerulonephritis + pulmonary haemorrhage
- Symmetrical joint swelling, morning stiffness, swan-neck deformity, boutonniere deformity, ulnar deviation of fingers
- Villous atrophy, abdominal pain, bloating, steatorrhoea, dermatitis herpetiformis (itchy blisters on elbows / knees / buttocks)
- Graves’ disease (type 2 / 5) –> anti-TSH receptor antibodies (90%) stimulate thyroid to release more thyroxine; anti-TPO (75%)
-
Hashimoto's
(type 2 + 4) –> anti-TPO; anti-thyroglobulin -
T1DM
(type 4) –> anti-islet cell; anti-insulin; anti-GAD (glutamate decarboxylase); anti-tyrosine phosphatase. NOTE: C-peptide is LOW in T1DM but NORMAL in MODY -
Pernicious anaemia
(type 2) –> anti-parietal cell; anti-intrinsic factor -
Myasthenia gravis
(type 2 / 5) –> Anti-nicotinic acetylcholine receptor; anti-MuSK. Mx = Pyridostigmine, if crisis plasmapheresis + IVIG -
Lambert-Eaton myasthenic syndrome (LEMS)
–> anti-voltage-gated calcium-channel antibody -
Goodpasture's disease
/ Anti-GBM disease (type 2) –> anti-GBM (type IV collagen) -
Rheumatoid arthritis
(type 3) –> anti-cyclic citrullinated peptide; polymorphisms in PAD2/PAD4 genes cause increased conversion of arginine to citrulline
NOTE: Felty’s = splenomegaly + neutropenia
-
Coeliac disease
(type 4) –> anti-tissue transglutaminase IgA; anti-endomysial; anti-gliadin antibodies (NOTE: gliadin deaminated by tTG then deaminated gliadin presented by APC, which triggers immune response to destroy that area of epithelial cells –> gold standard Ix = duodenal biopsy)
SUMMARY CARD:
What are the HLA associations with each of these polygenic autoimmune diseases:
- Ankylosing spondylitis
- Goodpasture’s syndrome
- Graves’ disease
- SLE
- T1DM
- RA
- Coeliac disease
- Ankylosing spondylitis = HLA-B27
- Goodpasture’s syndrome = HLA-DR15/DR2
- Graves’ disease = HLA-DR3
- SLE = HLA-DR3
- T1DM = HLA-DR3/4
- RA = HLA-DR4
- Coeliac = HLA-DQ2/8
SUMMARY CARD:
Polygenic autoimmune diseases: Connective tissue disease (ANA +ve) edition
Guess the diagnosis (type of hypersensitvity) + autoantibodies (+/- Mx)
-
Malar rash + arthralgia + pleurisy
after taking procainamide / hydralazine / isoniazid -
Malar rash, nephritis, pleuritis
etc.; associated with anti-phospholipid syndrome, low C3 and C4 in active disease -
Dry mouth and eyes
(confirmed with Schirmer’s test, < 5mm), bilateral parotid enlargement, arthralgia, myalgia, lymphoid malignancy -
CREST syndrome
– Calcinosis (calcium deposition in tissue/skin), Raynaud’s phenomenon, Esophageal dysmotility, Sclerodactyly (localised thickening of skin) and Telangectasia (small dilated blood vessels); skin involvement not below elbows/knees -
CREST
buttrunk and proximal limbs
predominantly affected, >1 organ system affected (diffuse rather than limited); respiratory involvement most common cause of death - Can be associated with underlying malignancy, photosensitive rash w/heliotrope rash in the periorbital region;
Gottron’s papules
(red papules over extensors);proximal muscle weakness
+/- tenderness; high CK + -ve EMG (normal muscle response) -
Proximal muscle weakness
+/- tenderness, ptosis, dysphagia; elevated CK BUTno skin manifestations
, EMG might be +ve -
Renal impairment
(↑creatinine), small vessel vasculitis, palpable purpura, cough + dyspnoea, systemic malignancy -
Saddle nose deformity
, URT: epistaxis, sinusitis, LRT: dyspnoea and haemoptysis; pauci-immune glomerulonephritis; renal biopsy:epithelial crescents
in Bowman’s capsule - Eosinophilia, asthma, mononeuritis multiplex paranasal sinusitis, M>F
-
Drug-induced lupus
: anti-histone antibodies; drug causes = procainamide and hydralazine (most common), isoniazid (less common) -
SLE
(type 3): anti-dsDNA (higher titre = more severe disease) OR anti-Smith (most specific but less sensitive); cytology: haematoxylin antibodies, antibody deposition in a granular lumpy-bumpy granules -
Sjogren's syndrome
: anti-Ro and anti-La; ↑ risk of MALT lymphoma; Mx = pilocarpine -
Limited cutaneous systemic sclerosis
: anti-centromere -
Diffuse systemic sclerosis
: anti-topoisomerase (SCL-70) antibody -
Dermatomyositis
: Anti-histidine-tRNA ligase (Jo-1) -
Polymyositis
: Anti-Jo-1 -
Microscopic polyangiitis
(type 3): pANCA (70%) + cANCA (45%) -
Wegener's granulomatosis
/ granulomatosis w/ polyangiitis (type 3): cANCA (antineutrophil cytoplasmic antibodies) -
Churg-Strauss syndrome
/ eosinophilic granulomatosis w/polyangiitis (type 3): pANCA (antineutrophil cytoplasmic antibodies)
SUMMARY CARD:
When staining for autoantibodies, a positive nuclear staining result can show which staining patterns?
miscellaenous (can skip)
Positive nuclear staining can show more detailed staining patterns: such as speckled, peripheral, or homogeneous
E.g.
Homogenous: anti-histone (drug induced SLE)
Peripheral: anti-dsDNA (SLE)
Speckled: Anti-Jo-1 (dermatomyositis), anti-Ro/anti-La (Sjogren’s), anti-Smith (SLE), anti-RNP (mixed connective tissue disease)
Nucleolar: anti-RNA polymerase (systemic sclerosis)
SUMMARY CARD:
What is the auto-antibody for:
Drug-induced lupus
SLE
Sjogren's syndrome
Limited cutaneous systemic sclerosis
-
Diffuse systemic sclerosis
: -
Dermatomyositis
: -
Polymyositis
: -
Microscopic polyangiitis
: -
Wegener's granulomatosis
/ granulomatosis w/ polyangiitis: -
Churg-Strauss syndrome
/ eosinophilic granulomatosis w/polyangiitis:
- Homogenous anti-histone antibodies
- Homogenous anti-dsDNA (higher titre = more severe disease) OR speckled anti-Smith (most specific but less sensitive)
- Speckled anti-Ro + anti-La
- Anti-centromere
- Anti-SCL-70 (topoisomerase) antibody
- Anti-Jo-1 (histidine-tRNA ligase)
- Anti-Jo-1
- pANCA + cANCA
- cANCA (cytoplasmic antineutrophil cytoplasmic antibodies)
- pANCA (perinuclear antineutrophil cytoplasmic antibodies)
SUMMARY CARD:
What are the 4 (or 5) types of hypersensitivity reactions?
-
Type 1 =
IgE
mediated
- Primary exposure results in sensitisation
- Plasma cells produce IgE abs
- IgE abs bind to antigens
- IgE crosslinks with mast cells / basophils –> triggers degranulation of these cells
- Results in release of histamines
- e.g. atopy, anaphylaxis
-
Type 2 =
antibodies bind to antifens on cell surface
- Binding of ab to ag = activation of phagocytes + NK cells via the Fc portion
- Causes autoimmune conditions (as autoantibodies result in destruction of self cells) e.g. Goodpasture’s
-
Type 3 = antibodies bind to antigens in the blood to form
immune complexes
- Immune complexes deposit in blood vessels / joints / organs and may cause inflammatory conditions e.g. SLE
-
Type 4 =
delayed reaction
driven by T-cells
- CD4+ cells release cytokines + CD8+ kills targetted cells
- Symptoms progress over a period of time e.g. T1DM, contact dermatitis, MS
-
Type 5 = Type 2 BUT when antibody binds to antigen on cell surface, it causes
MODULATION of cell function
e.g. Graves’
SUMMARY CARD:
How does a type 1 hypersentivity reaction develop?
Sesitisation then allergy
Sensitisation:
- TH2 cells primed by APCs in lymph nodes –> cytokine release
-
IL-4
promotes B-cell class switching to IgE - IgE binds to mast cells and primes them via the Fc region
-
IL-5
promotes eosinophils
Allergy:
- Months later, primed mast cells degranulate –> release of
histamines
, which cause smooth muscle contraction
SUMMARY CARD:
Type 1 hypersensitivity reaction
Guess the diagnosis (+/- Ix / Mx):
-
Angioedema + urticaria
; SOB, stridor, upper airway oedema/swelling - Allergic to e.g. pears but not if cooked (heat liable allergens); urticaria / Sx limited to mouth
- Ate wheat / shellfish / celery, then went to gym a few hours later –> develops SOB, urticaria, angioedema etc.
-
Anaphylaxis
: Mx = IM adrenaline 0.5mg 1:1000 (in paeds: < 6 years = 0.15mg, 6-12 years = 0.3mg, 12+ = 0.5mg);serial mast cell tryptase
= biomarker for anaphylaxis (peaks at 1-2 hrs) -
Oral allergy syndrome
: inhaled pollen generates IgE abs that are similar to antigens on other foors e.g. pears –> results in cross reaction -
Food associated exercise induced anaphylaxis
: anaphylaxis that only occurs if exercise is done 4-6 hours after food ingestion
SUMMARY CARD:
What are some conditions that can mimic anaphylaxis?
ACEi, hereditary angioedema
-
Hereditary angioedema: caused by
C1 inhibitor deficiency
–> recurrent episodes of throat swelling, FHx, hepatomegaly -
ACEi induced angioedema: significant upper airway angioedema associated with ACEi use,
does NOT respond to anti-histamines
SUMMARY CARD:
What are the allergy investigations?
derm, IgE blood test, basophil, serum tryptase, allergen challenge
1. Allergen specific tests –> look for sensitisation:
a) Dermatological e.g. skin prick testing
:
- Easy but ↑risk of false +ves; better than RAST (IgE measurements)
- GOLD STANDARD for pollen + food allergies
- Prick allergen into skin, alongside histamine (+ve control) and placebo (-ve control)
- Positive test result if allergen
wheel >3mm
wider than -ve control wheel
NOTE: intra-dermal = like skin-prick testing but deeper injection of allergen into skin –> ↑ sensitivity but ↑ risk of anaphylaxis (only done if skin prick -ve but HIGH clinical suspicion of allergy)
NOTE: patch test is for contact dermatitis (Delayed reaction)
b) Blood tests e.g. RAST
- Measures allergen-specific IgE
- Add patient’s serum to allergen –> add flourescently labelled IgE –> measure levels of anti-IgE
- Does NOT predict severity of reaction
NOTE: component resolved diagnostics is the same thing but blood test detects IgE against single protein rather than whole allergen (e.g. dfferentiate between peanut / hazelnut allergy)
2. Functional tests –> done in vitro:
a) Basophil activation test
:
- Expose basophils to allergen –> measure cell surface markers
- Difficult to standardise (so rarely used in clinical practice)
- Indicated as a surrogate for oral challenge
b) Serial mast cell tryptase
= marker for analyphlaxis (peaks at 1-2 hrs)
c) Allergen challenge
:
- Usually blinded
- GOLD STANDARD for food / drug allergy diagnosis
- Supervised exposure to increasing amounts of allergen
- ↑ risk of anaphylaxis; only done is doubt about diagnosis after skin test / RAST
SUMMARY CARD:
How does a Type 2 hypersensitivity reaction develop?
Error in central tolerance
process –> results in self-reactive B lymphocytes against cell surface antigens
IgM (RARE); IgG (COMMON)
Reaction can be intrinsic (self antigen) or extrinsic (reaction only occurs if taking medication during infection etc.)
SUMMARY CARD:
Diagnose the Type 2 hypersensitivity condition:
- Glomerulonephritis + pulmonary haemorrhage, anti-GBM
- Non-tense skin blistering, antibody against epidermal cadherin
- Bruising / purpura, anti-platelet antibody
Others in prev. flashcards e.g. Churg-Strauss (pANCA), Wegener’s (cANCA), MG (Anti ACh-R ab), Graves’ (Anti TSH-R ab), pernicious anaemia (anti parietal cell)
- Goodpasture’s
- Pemphigus Vulgaris
- Autoimmune thrombocytopenic purpura
SUMMARY CARD:
How does a Type 3 hypersensitivity reaction develop?
Self-reactive B-cell lymphocyte
(IgG) against SOLUBLE antigen (in the blood) –> therefore formation of Ag-Ab complexes
These immune complexes
are deposited in vessels / tissues = INFLAMMATION
+/- fibrinoid (tissue) necrosis + destruction
SUMMARY CARD:
Diagnose the Type 3 hypersensitivity reaction:
-
Nephritis, athritis, skin lesions
; anti-histone or anti-dsDNA - Systemic vasculitis, fever, fatigue, weakness, arthralgia, Hep B, pericarditis, skin/renal involvement; antibody against
Hep B
/C; HIGH WCC / ESR / CRP - Develop rashes, itching, athralgia, fever, lymphadenopathy over 7-12 days; reaction to proteins in anti-serum (penicillin); LOW C3
- anti-histone =
drug induced lupus
–> Mx = discontinue precipitation drug +/- administer steroid, anti-dsDNA =SLE
–> Mx = analgesia + steroids + cyclophosphamides -
Polyarteritis nodosa (PAN)
–> Mx = prednisolone + cyclophosphamide - Serum sickness = discontinue precipitant, administer steroids + antihistamines
SUMMARY CARD:
How does a Type IV hypersensitivity reaction develop?
Delayed reaction, T-cell mediated
Similar to how body responds to virus or cancer, foreign antigen is picked up by dendritic cell + presented to naive T-cells –> triggers either:
- CD4+ (macrophage recruitment) = ROS generation, lysozymes, inflammatory cytokines
- OR CD8+ = apoptosis + programmed cell death w/ perforin / granzymes
SUMMARY CARD:
Guess the Type 4 hypersensitivity reaction:
- Two or more CNS lesions with corresponding symptoms, separated in time and space (MacDonald Criteria) -
demyelinating disease
, optic neuritis, neurological Sx (muscle weakness, sensory disturbance, GI, autonomic etc.), relapsing-remitting; MRI: white matter lesions - Tuberculin –> skin induration + erythema
Others in previous flashcards: T1DM (anti-islet, anti-insulin), RA (anti-CCP), Hashimoto’s (anti-TPO, anti-thyroglobulin), contact dermatitis, Crohn’s disease
- Multiple sclerosis
- Mantoux test
SUMMARY CARD:
How are transplant donors and recipients matched?
Important to match human leucocyte antigen (HLA)
HLA class 1: A / B / C
= found on ALL cells
HLA class 2: DR / DQ / DP
= found on APC only
HLA mismatch can lead to potential rejection of transplanted organ
Donor + recipient HLA matched at pre-op; order of importance:DR > B > A
(so HLA-C and HLA-DP groups aren’t as important in terms of rejection outcomes)
SUMMARY CARD:
What are the 5 types of transplant rejections?
hyperacute, T-cell, Ab, chronic, GvHD
-
Hyperacute
(mins-hrs): typically if there are pre-formed antibodies to HLA or ABO (due to prior sensitisation event e.g. pregnancy, transfusion, etc.); Sx = thrombosis, necrosis, fever -
Acute T-cell mediated
(wks-months): type 4 hypersensitivity reaction, donor HLA presented on host APCs –> T-cell activation; Sx =interstitial inflammation
-
Acute antibody mediated
(months-yrs): recipient MHC picks up donor proteins –> anti-HLA antibodies formation –> antibodies bind to graft endothelium = intravascular disease + organ damage; Sx =capillaritis
-
Chronic
(months-yrs): immune + non-immune mechanisms = blockage of graft vessel lumens –> ischaemia + fibrosis -
GvHD w/ SCT
(days-wks): donor lymphocytes target host tissue; prophylaxis =methotrexate / ciclosporin
; Sx = diarrhoea, bloody stool, abdo pain, N&V, rash, jaundice, Mx = steroids
DISEASE:
Thrombosis + necrosis + fever an hour after transplant
- What is the diagnosis?
- What type of hypersensitivity reaction is this?
- Mx?
Hyperacute
: develops within mins-hrs
Typically there are pre-formed antibodies to HLA or ABO due to prior sensitisation event e.g. pregnancy, transfusion, etc.
Type 2 mediated reaction - recipient antibodies bind to antigens on graft
PREVENT by HLA & ABO matching
DISEASE:
Interstitial inflammation
1 month after transplant –> eventually organ damage
Rise in Cr
Histology: lymphocytic interstitial infiltration + ruptured tubular BM + tubulitis
- What is the diagnosis?
- What are the 3 pathways to develop this reaction?
- Mx?
Acute T-cell mediated
: develops over weeks to months
Type 4 hypersensitivity reaction
3 pathways:
1. Direct pathway = donor APC (e.g. dendritic cell) and donor MHC presenting donor protein is presented to recipient’s immune cells, which stimulates immune response
2. Indirect pathway = proteins from donor released (e.g. when the cells naturally die) –> recipient immune system picks them up and presents them on recipient’s APC, which stimulates immune response
3. Semi-direct pathway = donor MHC presenting donor protein is picked up by recipient APC, which stimulates immune response
Cytotoxic T-cells cause organ damage and interstital inflammation
Mx = T-cell immunosuppression with steroids, tacrolimus / cyclosporin (calcineurin inhibitors)
DISEASE:
Vascular rejection (endothelial damage) after weeks / months
Pro-coagulation + graft fibrosis
Histology: vasculitis
(capillaritis
)
- What is the diagnosis?
- Pathophysiology?
- Mx?
Acute antibody mediated
: develops over weeks to months
B-cell activation = antibody attacks vessels
Mx = Ab removal (e.g. plasmapheresis) + B-cell suppression e.g. rituximab = anti-CD20
DISEASE:
What is plasmapheresis and what are its indications?
Treat patient’s plasma to remove Igs then re-infuse
back into patient
Indications: Type II hypersentivity reaction (e.g. Goodpasture’s, MG), antibody mediated transplant rejection (e.g. anti-HLA abs)
SEs: rebound Ab production afterwards (therefore typically given with anti-proliferative agent
)
DISEASE:
Smooth muscle growth + blockage of graft vessel lumens, ischaemia, fibrosis
>6 months after transplant
RFs: multiple acute rejections, HTN, hyperlipidaemia, HLA mismatches
Histology: fibrosis
, ischaemia, glomerulopathy (kidney) or bronchiolitis obliterans (lungs)
- What is the diagnosis +/- underlying mechanism?
Chronic rejection
–> typically occurs >6 months after transplant
Due to immune and non-immune mechanisms –> leads to fibrosis of transplanted organ
DISEASE:
Sx following transplant:
Skin desquamation / rash
GI disturbance (N&V, abdominal pain, diarrhoea, bloody stool)
Liver failure
Bone marrow failure
- What is the diagnosis?
- What is the underlying mechanism?
- Mx? (BONUS: prophylaxis medications?)
IMPORTANT!
Graft vs Host Disease (GvHD)
= ONLY occurs after HSCT
Irreversible attack of donor lymphocytes on recipient HLA
Related to degree of HLA incompatibility
Prophylaxis
: methotrexate / ciclosporin, irradiate blood components for immunosuppressed ptsMx
= corticosteroids
SUMMARY CARD:
What is immune modulation?
Can either:Boost immune response:
* Vaccination +/- adjuvants
* Replacement of missing components
* Cytokine therapy
* Blocking immune checkpoints (e.g. for advanced melanoma)
OR suppress the immune response:
* Steroids
* Anti-proliferative agents
* Plasmapheresis
* Inhibitors of cell signalling
* mAbs directed at cell surface antigens
* mAbs directed at cytokines +/- their receptors
SUMMARY CARD:
What are passive vaccines?
Examples of passive vaccines:
Vaccine containing pre-formed Abs / Igs
Lasts for ~3 weeks
* HNIG (human normal Ig) = Hep A, measles
* HBIG (hep B Ig) = hep B
* HRIG (human rabies Ig) = rabies
* VZIG (varicella zoster Ig) = varicella
* Paviluzumab = mAb for RSV
SUMMARY CARD:
What are the different types of active vaccines?
- Live attenuated vaccines
- Subunit (recombinant) vaccines
- Conjugate vaccines
- Inactivated vaccines
-
Live attenuated vaccines = e.g.
BCG
for TB,MMR, Yellow Fever
; these are avoided in pregnancy and immunocompromised patients -
Subunit (recombinant) vaccines = typically for
viruses
e.g. Hep B and HPV; vaccine contains proteins found on the surface of the viruses in addition to an adjuvant -
Conjugate vaccines = for
encapsulated bacteria
e.g. haemophilus influenzae, meningococcus and pneumococcus; consists of bacterial polysaccharides conjugated to an immunogenic toxin -
Inactivated vaccines = e.g.
pertussis
; vaccine where the pathogen had been rendered inert - usually by heat killing or formaldehyde; pathogen cannot replicate, it usually requires multiple booster shots to provide immunity
DISEASE:
What are the ideal vaccine requirements? (for active vaccines)
- Generates immunological memory
- Practical - single injection, easy storage, inexpensive
- No adverse effects
SUMMARY CARD:
What is the UK vaccine programme?
2 months
: 6 in 1 (diptheria, polio, tetanus, pertussis, HiB, Hep B); rotavirus; Men B
3 months
: 6 in 1 2nd dose (diptheria, polio, tetanus, pertussis, HiB, Hep B); rotavirus 2nd dose; pneumococcal (PCV)
4 months
: 6 in 1 3rd dose (diptheria, polio, tetanus, pertussis, HiB, Hep B); Men B 2nd dose
1 year
: HiB/MenC; Men B 3rd dose; pneumoccocal vaccine 2nd dose; MMR
3 years 4 months
: 4 in 1 booster (diptheria, pertussis, polio, tetanus); MMR
12-13 years
: HPV
14 years
: 3 in 1 booster (diptheria, tetanus, polio)
SUMMARY CARD:
What are the adult vaccines?
18 years: MenACWY
50 years onwards: flu vaccine
65 years: pneumococcal (PCV) vaccine
70 years: shingles
Pregnancy (any age): flu vaccine, 4 in 1 (diptheria/tetanus/pertussis/polio) from16/40 gestation
SUMMARY CARD:
Which are the live attenuated vaccines?
Which are the inactivated / component vaccines?
Live attenuated = MMR-VBOY
MMR
VZV
BCG
- Oral - polio, typhoid
- Yellow fever
- Influenza
Inactivated = influenza, polio, cholera, bubonic plague, Hep A, rabies, pertussis, anthrax
Component/subunit = Heb B (HbS antigen), HPV (capsid), influenza recombinant
DISEASE:
How to adjuvants / depots work (to enhance vaccine response)?
More persistent antigen (slow release antigen = prolonged response)
+ stimulant assists immune activation
SUMMARY CARD:
What are different immunsuppressive drugs?
-
Steroids
= phospholipase A2 inhibitors = ↓ prostaglandins = ↓ inflammation -
Anti-proliferative agents
= e.g. cyclophosphamide (alkylates guanine), azathioprine (metabolised to 6 metacaptopurine, bone marrow suppression if TPMT polymorphism), mycophenolate mofetil (JC virus = PML), methotrexate (inhibits dihydrofolate reductase) -
Anti-cell signalling agents
= e.g. calcineurin inhibitors (e.g. tacrolimus, ciclosporin), tofacitinib (JAKi), aprelimast (PDE4i =↑ cAMP), IL-2 pathway inhibitor (e.g. sirolimus, rapamycin) -
mAbs against cell surface antigens
= e.g. Rituximab (MHL, RA), Vedolizumab (IBD), Natalizumab (MS), Tocilizumab (RA, Castleman’s disease), Basiliximab/Daclizumab (organ transplant rejection prophylaxis) -
mAbs against cytokines+/- their receptors
= e.g. anti-TNFa (e.g. infliximab, adalimumab, certolizumab, golimumab, SE = reactivation of TB), etanercept (anti-TNFa receptor - RA, AS), psoriasis/psoriatic arthritis (e.g. usteki/guselk/secukin -umab), denosumab (osteoporosis, SE = avascular necrosis of jaw), anakinra (IL-1 antagonist, FMF)
SUMMARY CARD:
Steroids e.g. prednisolone
- Mechanism of action?
- Indications?
- SEs?
- Inhibition of
phospholipase A2
–> no breakdown of phospholipids to arachidonic acid = prostaglandin synthesis blocked = reduced inflammation - Indicated in: allergy, renal disorders, malignancy
- S/Es: transient neutrophilia, Cushing’s syndrome / steroid induced diabetes mellitus
SUMMARY CARD:
What are some anti-proliferative agents?
- Cyclophosphamide
- Azathioprine
- Mycophenolate mofetil
- Methotrexate
SUMMARY CARD:
State the mechanism of action, indications and side effects of each of the anti-proliferative agents:
- Cyclophosphamide
- Azathioprine
- Mycophenolate mofetil
- Methotrexate
-
Cyclophosphamide
: alkylating agent (alkylates guanine in DNA) = damages DNA and prevents cell replication
- Affects B cells > T cells
- Indications: connective tissue disease, vasculitis w/end-organ damage, anti-cancer agent
- SEs: sterility (M>F), hair loss, bladder cancer, haematological malignancy, haemorrhagic cystitis (Due to toxic drug metabolite in urine)
-
Azathioprine
: anti-metabolite, metabolised by liver to 6 mercaptopurine and blocks de novo purine synthesis, which prevents DNA replication
- Affects T cells > B cells
- Indications: transplants, AI disease, autoinflammatory disease
- SEs: bone marrow suppression in those with thiopurine methyltransferase (TPMT) polymorphism as they cannot metabolise the drug; pancreatitis, hepatotoxicity
-
Mycophenolate mofetil
: Inhibits inosine monophosphate dehydrogenase (IM PDH), which prevents guanine synthesis synthesis = prevents DNA replication
- Affects T-cells > B-cells
- Indications: transplantation, vasculitis (as an alternative to cyclophosphamide)
- Reactivation of herpes, progressive multifocal encephalopathy (
John-Cunningham virus
)
-
Methotrexate
: Inhibits dihydrofolate reductase = decreases DNA synthesis
- Indications: RA, SLE, psoriasis, Crohn’s, ectopic pregnancy abortions, chemotherapy
- SEs: macrocytic megaloblastic anaemia, bone marrow suppression, loss of appetite, depression
SUMMARY CARD:
What are some medications that inhibit cell signalling?
- Calcineurin inhibitors e.g. Tacrolimus, ciclosporin
- Tofacitinib
- Aprelimast
- IL-2 pathway inhibitor e.g. sirolimus, rapamycin
SUMMARY CARD:
State the mechanism of action, indications and side effects of each of the anti-cell signalling agents:
- Tacrolimus, ciclosporin
- Tofacitinib
- Aprelimast
- Sirolimus, rapamycin
-
Tacrolimus
: calcineurin inhibitor = ↓ IL-2 function = ↓ T-cell proliferation
- Indications: rejection prophylaxis (
t
ransplant), SLE, psoriatic arthritis - SEs: nephrotoxic, hypertension, neurotoxic, diabe
t
ogenic
-
Ciclosporin
: calcineurin inhibitor = ↓ IL-2 function = ↓ T-cell proliferation
- Indications: transplantation
- SEs: nephrotoxic, hypertension, gum hyperplasia, dysmorphic features
-
Tofacitinib
: JAK 1/3 inhibitor = ↓ JAK-STAT signalling pathway = ↓ production of inflammatory molecules
- Indications: arthritides (rheum, psoriatic)
-
Aprelimast
: phosphodiesterase 4 inhibitor (phosphodiesterase normally breaks down cAMP) = ↑ cAMP = inhibits activation of transcription factors
- Indications: psoriasis +/- psoriatic arthritis
-
Sirolimus, rapamycin
: IL-2 pathway inhibitor e.g. sirolimus, rapamycin: mTOR inhibitor = inhibits IL-2 pathway = ↓ T-cell proliferation
- Indications: transplant
- SEs: hypertension (but LESS nephrotoxic than the calcineurin inhibitors)
SUMMARY CARD:
What do these suffixes of the mAbs mean?
1. -umab
2. -ximab
3. xumab
4. bonus: ‘tu’
5. bonus: ‘os’
- -umab = fully human
- -zumab = humanised
- -ximab = chimeric
- if the drug name has ‘
tu
’ before the suffix, it acts agains atu
mour - if the drug name has ‘
os
’ before the suffix, it acts against bone (os
teopororis?)
SUMMARY CARD:
What are some mAbs directed against cell surface antigens (AKA block cell signalling)?
-
Basiliximab
= antiCD25 –> organ transplant rejection prophylaxis -
Daclizumab
= anti-CD25 + IL-2 receptor Ab –> organ transplant rejection prophylaxis -
Rituximab
= anti-CD20 –> non-Hodgkin’s lymphoma, RA -
Vedolizumab
= anti-a4-b7 integrin –> IBD -
Natalizumab
= anti-a4-b1 integrin –> remitting relapsing MS -
Tocilizumab
, Sarilumab = anti-IL-6 receptor –> Castleman’s disease (IL-6 producing tumour) -
Muromonab
= mouse anti-CD3 –> active cell-mediated rejection of transplant -
Anti-thymocyte globulin
= lymphocyte depletion –> heart/renal transplant rejections -
Abatecept
= anti-CTLA4 –> RA -
Efalizumab
= Anti-CD11a –> psoriasis -
Alentuzumab
= anti-CD52 –> chronic lymphoid myeloma (CLL), MS
SUMMARY CARD:
State the mechanism of action, indications and side effects
of each of the mAbs directed against cell surface antigens:
- Basiliximab
- Daclizumab
- Rituximab
- Vedolizumab
- Natalizumab
- Tocilizumab, Sarilumab
- Muromonab
- Anti-thymocyte globulin
- Abatecept
- Efalizumab
- Alentuzumab
-
Basiliximab
: antiCD25 (alpha chain of IL-2 receptor) = inhibits T-cell proliferation
- Indications: organ transplant rejection prophylaxis
- SEs: infusion reaction, infection, potential malignancy
-
Daclizumab
= anti-CD25 (alpha chain of IL-2 receptor) AKA IL-2 receptor Ab –> organ transplant rejection prophylaxis
- Indications: organ transplant rejection prophylaxis
- SEs: infusion reaction, infection, potential malignancy
-
Rituximab
: anti-CD20 = depletes mature B cells
- Indications: Non-Hodgkin’s lymphoma, RA
- SEs: infusion reaction, reactivation of hep B, exacerbation of CV disease
-
Vedolizumab
: anti-a4-b7 inegrin = prevents T-cell migration
- Indications: IBD
- SEs: infusion reaction, hepatotoxicity
-
Natalizumab
: anti-a4-b1 integrin = prevents T cell migration
- Indications: active / remitting relapsing MS
- SEs: John Cunningham Virus –> PML (progressive multifocal leukoencephalopathy)
-
Tocilizumab
, Sarilumab: anti-IL-6 receptor = reduced macrophage / T-cell / B-cell / neutrophil activation
- Indications: Castleman’s disease (IL-6 producing tumour), RA
- SEs: elevated lipids and hepatotoxicity (so LFTs and cholesterol has to be measured regularly)
-
Muromonab
:m
ouse anti-CD3
- Indications: active cell-mediated rejection of transplant
- SEs: fever, leucopenia, anaphylaxis
-
Anti-thymocyte globulin
: lymphocyte depletion via modulation of T-cell activation + migration
- Indications: heart/renal transplant rejections
- SEs: fever, leucopenia
-
Abatecept
= anti-CTLA4-Ig fusion protein = reduced T cell activation
- Indications: RA w/ resistance to DMARDS
- SEs: infusion reaction, infection, potential malignancy
-
Efalizumab
: Anti-CD11a = inhibits migration of T-cells
- Indications: psoriasis
-
Alentuzumab
= anti-CD52 (CD52 found on lymphocytes) = depletion of lymphocytes
- Indications: chronic lymphoid myeloma (CLL), MS
- SEs: CMV infection
DISEASE:
Which mAb is used in RA?
Which mAb is used in RA resistant to DMARDs?
Rituximab
DMARD-resistant RA = abatacept
DISEASE:
Which mAbs are organ transplant rejection prophylactic?
Anti-CD25 (alpha chain of IL-2 receptor) mAbs = basiliximab, daclizumab
DISEASE:
Which mAb is used for IBD?
Vedolizumab
DISEASE:
Which mAb is used in relapsing-remitting / active MS?
Natalizumab
Or Alemtuzumab
DISEASE:
Which mAb is used for Castleman’s disease?
Tocilizumab, sarilumab = anti-IL-6
DISEASE:
Which mAb is used in CLL?
Alemtuzumab
SE = CMV infection
SUMMARY CARD:
What are some mAbs directed at cytokines / receptors?
-
Infliximab
= anti-TNFa –>IBD, RA, psoriasis
-
Adalimumab, Certolizumab, Golimumab
= anti-TNFa –> RA, AS, psoriasis / psoriatic arthritis -
Etanercept
: TNF-alpha antagonist -
Ustekinumab
= anti IL-2 / IL-23 (binds to p40 subunit) –> psoriasis / psoriatic arthritis -
Guselkumab
= anti IL-23 (inhibition of p19 subunit) –> psoriasis / psoriatic arthritis -
Secukinumab
= Anti-IL17A –> psoriasis / psoriatic arthritis -
Denosumab
= anti-RANKL antibody = prevention of bone resorption –> osteoporosis, (only medication that increases bone density), MM (multiple myeloma) -
Anakinra
= IL-1 antagonist –> FMF, gout
SUMMARY CARD:
State the mechanism of action, indications and side effects
of each of the mAbs directed against cytokines +/- receptors:
- Infliximab
- Adalimumab, Certolizumab, Golimumab
- Etanercept
- Ustekinumab
- Guselkumab
- Secukinumab
- Denosumab
- Anakinra
-
Infliximab
: anti-TNFa
- Indications: IBD, RA, psoriasis
- SEs: Infusion/injection site reactions, TB infection (do Mantoux before starting anti-TNF)
-
Adalimumab
(fully human mAb),Certolizumab, Golimumab
: anti-TNFa
- Indications: RA, ankylosing spondylitis
- SEs: infusion/injection site reaction, infection (TB, HBV, HCV), demyelination
-
Etanercept
: TNF-alpha antagonist
- Indications: RA, ankylosing spondylitis (NOTE: not useful in IBD)
- SEs: Injection site reaction, Infections (TB, HCV, HBV), demyelination
-
Ustekinumab
: anti IL-2 / IL-23 (binds to p40 subunit)
- Indications: psoriasis, psoriatic arthritis
- SEs: injection site reaction, infection (TB)
-
Guselkumab
: anti IL-23 (inhibition of p19 subunit)
- Indications: psoriasis, psoriatic arthritis
- SEs: injection site reaction, infection (TB)
-
Secukinumab
: anti-IL17A
- Indications: psoriasis, psoriatic arthritis
- SEs: injection site reaction, infection (TB)
-
Denosumab
: Anti-RANKL antibody = prevention of bone resorption
- Indications: osteoporosis (only medication that increases bone density, multiple myeloma
- SEs: avascular necrosis of jaw
-
Anakinra
: IL-1 antagonist
- Indications: familial mediterranean fever (FMF), gout
DISEASE:
Which mAb is used to treat osteoporosis?
BONUS: what is the top SE?
Denos
umab –> inhibits anti-RANK ligand
SE: avascular necrosis of jaw
DISEASE:
Which 3 mAbs are used in psoriasis / psoriatic arthritis?
Ustekinumab
Guselkumab
Secukinumab
DISEASE:
Which mAb is a TNF-alpha receptor inhibitor?
Etanercept –> used for RA, AS
DISEASE:
Which mAb is used to treat FMF?
Anakinra = IL-1 antagonist
DISEASE:
What test is vital before prescribing anti-TNF alpha mAb?
Hint: may reactivate this infection (cough cough)
Mantoux test –> test for TB before prescribing
SUMMARY CARD:
What are cytokines?
Cytokines, proteins produced by various cells (e.g. immune, haematopoietic, and endothelial cells) are important for cell signalling.
Examples: chemokines, interferons, interleukins, TNF-α
SUMMARY CARD:
What are Type 1 and Type 2 interferons responsible for?
- Type 1 = IFN-alpha + IFN-beta –> produced by immune and non-immune cells
- Type 2 = IFN-gamma –> produced immune cells, primarily T cells, natural killer cells and macrophages
- Role of
IFN-gamma = macrophage activation
(e.g. in TB, IFN-gamma is elevated)
SUMMARY CARD:
Examples of interleukins and their functions:
-
IL-1
: proinflammatory, activation of T and B lymphocytes, macrophages, endothelium -
IL-2
(T cell growth factor): proliferation/activation of T and B lymphocytes -
IL-4
: activation of B lymphocytes, suppression of Th1 lymphocytes, differentiation of CD4 cells to Th2 lymphocytes -
IL-5
: activation of eosinophils -
IL-6
: proinflammatory, differentiation of T and B cells, activation of haematopoietic stem cells -
IL-8
: activation of neutrophils -
IL-10 + IL-12
: suppression of macrophages and Th1 lymphocytes, B cell activation
DISEASE:
Which interleukins are pro-inflammatory?
IL-1 + IL-6
DISEASE:
Which interleukin is responsible for T-cell proliferation?
IL-2
DISEASE:
Which interleukins are anti-inflammatory (help counterbalance effects of inflammation)?
IL-10 (+IL-12)
SUMMARY CARD:
Which cells produce which interleukins?
- Dendritic cells - IL-1, IL-12
Th1 cells - IL-2
- Th2 cells - IL-4, IL-5, IL-6, IL-10
- Macrophages - IL-1, IL-4, IL-6, IL-10, IL-12
- Mast cells - IL-5
SUMMARY CARD:
- How does HIV enter cells?
- What is the immune response to HIV?
- How is HIV screened and confirmed?
- HIV is an RNA retrovirus –> glycoprotein 120 binds to CD4+ and co-receptor CCR5/CXCR4 (so mutation in this = HIV resistant)
- Immune response:
- Innate = macrophage / NK / complement / dendritic cells
- Adaptive = neutralising (bind to antigens on HIV to prevent it from binding + entering CD4+ cells) + non-neutralising antibodies (bind to antigens on virus infected cells to signal to macrophages to phagocytose)
- Neutralising Abs =
anti-gp41 IgM
(first weeks),anti-gp120
(later) - Non-neutralising Abs =
anti-p24 gag IgG
-
Screening test
: ELISA detects anti-HIV antibody (IgG/IgM)
NOTE: unreliable in babies as Igs may be passed from mum to baby in utero / via breastmilkConfirmation test
: Western Blot test detects Abs (takes 15-45 days since infection until +ve)
SUMMARY CARD:
- What are the next steps after confirmation of HIV diagnosis?
- Mx?
-
PCR is used to detect viral load + FACS used to assess CD4 count (
< 200 cells/uL in blood = AIDS
) - ALL HIV +ve patients are to commence HAART immediately (don’t need to rely on CD4+ count)
- Highly active anti-retroviral therapy (HAART) =
2NRTIs + PI (or NNRTI)
- In pregnancy:
Zidovudine
(PO antepartum; IV during delivery) –> reduced transmission risk from 26% to 8% - Monitoring: regular viral loads, CD4+ monitoring not needed if > 350 cells/uL of blood, monitor liver/kidney/bone/lipid toxicity
DISEASE:
What is the receptor via which HIV enters?
Co-receptor CCR5/CXCR4 (so mutation in this = HIV resistant)
DISEASE:
What are the antibodies produced against an HIV infection?
-
Neutralising Abs =
anti-gp41 IgM
(first weeks),anti-gp120
(later) -
Non-neutralising Abs =
anti-p24 gag IgG
DISEASE:
What is the screening test vs the confirmation test?
BONUS: what are their limitations?
-
Screening test
: ELISA detects anti-HIV antibody (IgG/IgM)
Limitation = unreliable in babies as Igs may be passed from mum to baby in utero / via breastmilk -
Confirmation test
: Western Blot test detects Abs
Limitation = takes 15-45 days since infection until +ve
DISEASE:
What is the anti-retroviral given in pregnancy?
Zidovudine
PO antepartum, IV during delivery
DISEASE:
At what CD4+ count is HIV considered AIDS?
< 200 cells u/L of blood
BONUS - important CD4+ counts and opportunistic infections:
- 75 - mycobacterium avium complex disease; PCP (caused by pneumocystis jirovecii)
- 300-350 - pulmonary TB
- 400 - Kaposi sarcoma (HHV-8)
DISEASE:
What antibodies are associated with anti-phospholipid syndrome?
anti-cardiolipin + anti-B2 glycoprotein
DISEASE:
Rapidly progressive glomerulonephritis
Nosebleeds
Haemoptysis
- Diagnosis?
- BONUS: which gene?
Wegener’s (Granulomatosis with Polyangitis)
cANCA