Immunology EMQs Flashcards

1
Q
A Kostmann syndrome
B Severe combined immunodeficiency
C Hyper IgM syndrome
D Leukocyte adhesion deficiency
E Protein-losing enteropathy
F Cyclic neutropenia
G Bruton’s agammaglobulinaemia
H Di George’s syndrome
I AIDS

A 4-month-old girl is referred to a paediatrician with failure to thrive, after
suffering from recurrent infections since birth, especially recurrent candida
infections of her skin and mouth. Blood tests reveal a diminished T-cell count;
further lymphocyte testing demonstrates non-functional B cells.

A

B Severe combined immunodeficiency

Severe combined immunodeficiency (SCID; B) causes defects in both
T cells and B cells. The most common subtypes can be categorized into
an X-linked disease (mutation of IL-2 receptor) or an autosomal recessive
condition (mutation of adenosine deaminase gene which leads to
a build-up of toxins and hence compromised proliferation of lymphocytes).
Characteristically, there is hypoplasia and atrophy of the thymus
and mucosa-associated lymphoid tissue (MALT). Clinical features
include diarrhoea, failure to thrive and skin disease (graft-versus-host
induced, secondary to transplacental maternal T cells or blood transfusion-
related caused by donor T cells).

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2
Q
A Kostmann syndrome
B Severe combined immunodeficiency
C Hyper IgM syndrome
D Leukocyte adhesion deficiency
E Protein-losing enteropathy
F Cyclic neutropenia
G Bruton’s agammaglobulinaemia
H Di George’s syndrome
I AIDS

A 5-month-old boy is referred to a paediatrician after suffering with recurrent
infections since his birth. His mother has noticed increased irritability. Blood
tests reveal a neutrophil count of 350/μL. NBT test is normal.

A

A Kostmann syndrome

Kostmann syndrome (severe congenital neutropenia; A) is a congenital
neutropenia as a result of failure of neutrophil maturation. This results
in a very low neutrophil count (less than 500/μL indicates severe neutropenia)
and no pus formation. Kostmann syndrome is usually detected
soon after birth. Presenting features may be non-specific in infants,
including fever, irritability and infection. The nitro-blue-tetrazolium
(NBT) test can help with diagnosis; the liquid turns blue due to the normal
presence of NADPH. In Kostmann syndrome, NBT test is positive
and therefore normal.

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3
Q
A Kostmann syndrome
B Severe combined immunodeficiency
C Hyper IgM syndrome
D Leukocyte adhesion deficiency
E Protein-losing enteropathy
F Cyclic neutropenia
G Bruton’s agammaglobulinaemia
H Di George’s syndrome
I AIDS

A 4-year-old girl is referred to a paediatrician after experiencing recurrent
chest infections. Blood tests demonstrate a reduced B-cell count as well as low
IgA, IgM and IgG levels.

A

G Bruton’s agammaglobulinaemia

Bruton’s agammaglobulinaemia (G) is an X-linked disease that presents
in childhood. It is caused by a mutation of the BTK gene, which
expresses a tyrosine kinase. This mutation inhibits B-cell maturation
and therefore B-cell and immunoglobulin levels are diminished. Blood
tests will reveal a normal T-cell count, but diminished B-cell count as
well as IgA, IgM and IgG levels. Plasma cells will also be absent from
the bone marrow and lymphatics.

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4
Q
A Kostmann syndrome
B Severe combined immunodeficiency
C Hyper IgM syndrome
D Leukocyte adhesion deficiency
E Protein-losing enteropathy
F Cyclic neutropenia
G Bruton’s agammaglobulinaemia
H Di George’s syndrome
I AIDS

A 48-year-old woman presents to her GP with a history of diarrhoea for
3 weeks, which occasionally contains blood. She has felt increasingly tired and
feverish. The patient has had similar episodes in the past which were treated
with mesalazine. She also reports recurrent chest infections since her first episode
of diarrhoea.

A

E Protein-losing enteropathy

Protein-losing enteropathy (E) is defined as the severe loss of proteins
via the gastrointestinal tract. The underlying pathophysiology may
relate to mucosal disease, lymphatic obstruction or cell death leading to
increased permeability to proteins. If more proteins are lost than synthesized
in the body, hypoproteinaemia will result. Causes include Crohn’s
disease, coeliac disease and rarely, Menetrier’s disease. Hypoproteinaemia
secondary to such conditions results in fewer immunoglobulins being
formed which diminishes the adaptive immune response.

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5
Q
A Kostmann syndrome
B Severe combined immunodeficiency
C Hyper IgM syndrome
D Leukocyte adhesion deficiency
E Protein-losing enteropathy
F Cyclic neutropenia
G Bruton’s agammaglobulinaemia
H Di George’s syndrome
I AIDS

A 3-year-old girl is seen by a GP due to recurrent mild chest infections. The
doctor notices the girl has a cleft lip. Blood tests reveal a reduced T-cell count
as well as hypocalcaemia.

A

H Di George’s syndrome

Di George’s syndrome (H) is caused by an embryological abnormality
in the third and fourth branchial arches (pharyngeal pouches) due to a 22q11 deletion. The result is an absent or hypoplastic thymus, as well
as a deficiency in T cells. There is a reduction or absence of CD4+ and
CD8+ T cells as well as decreased production of IgG and IgA. B cell and
IgM levels are normal. The features of Di George’s syndrome can be
remembered by the mnemonic ‘CATCH’: cardiac abnormalities, atresia
(oesophageal), thymic aplasia, cleft palate and hypocalcaemia.

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6
Q
A Selective IgA deficiency disease
B Common variable immunodeficiency
C Nephrotic syndrome
D Bare lymphocyte syndrome
deficiency
E Sickle cell anaemia
F Chronic granulomatous
G Reticular dysgenesis
H Wiskott–Aldrich syndrome
I Interferon-gamma receptor

A 4-year-old boy is referred to a paediatrician after suffering recurrent chest
infections over the preceding few months. The boy has a history of eczema as
well as recurrent nose bleeds. Blood tests reveal a reduced IgM level but raised
IgA and IgE levels.

A

H Wiskott–Aldrich syndrome

Wiskott–Aldrich syndrome (WAS; H) is an X-linked condition which is
caused by a mutation in the WASp gene; the WAS protein is expressed
in developing haematopoietic stem cells. WAS is linked to the development
of lymphomas, thrombocytopenia and eczema. Clinical features
include easy bruising, nose bleeds and gastrointestinal bleeds secondary
to thrombocytopenia. Recurrent bacterial infections also result. Blood
tests reveal a reduced IgM level and raised IgA and IgE levels. IgG levels
may be normal, reduced or elevated.

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7
Q
A Selective IgA deficiency disease
B Common variable immunodeficiency
C Nephrotic syndrome
D Bare lymphocyte syndrome
deficiency
E Sickle cell anaemia
F Chronic granulomatous
G Reticular dysgenesis
H Wiskott–Aldrich syndrome
I Interferon-gamma receptor

A 20-year-old man presents to his GP with signs of a mild pneumonia. The
patient states he has had several similar episodes in the past. Further investigations
by an immunologist reveal the patient has a genetic condition caused by a
mutation of MHC III.

A

B Common variable immunodeficiency

Common variable immunodeficiency (CVID; B) presents in adulthood. A
mutation of MHC III causes aberrant class switching, increasing the risk
of lymphoma and granulomas. Patients with CVID also have a predisposition
to developing autoimmune diseases. Recurrent infections caused
by Haemophilus influenzae and Streptococcus pneumoniae are common.
Clinical sequelae include bronchiectasis and sinusitis. Blood tests reveal
a reduced B-cell count, a normal/reduced IgM level and decreased levels
of IgA, IgG and IgE.

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8
Q
A Selective IgA deficiency disease
B Common variable immunodeficiency
C Nephrotic syndrome
D Bare lymphocyte syndrome
deficiency
E Sickle cell anaemia
F Chronic granulomatous
G Reticular dysgenesis
H Wiskott–Aldrich syndrome
I Interferon-gamma receptor

A 3-year-old girl is referred to a paediatrician after concerns about recurrent
skin infections she has suffered from since birth. A nitro-blue-tetrazolium test
is negative (remains colourless).

A

F Chronic granulomatous

Chronic granulomatous disease (F) is an X-linked disorder causing deficiency
of NADPH oxidase. As a result, neutrophils cannot produce the respiratory burst required to clear pathogens. The disease is characterized
by chronic inflammation with non-caseating granulomas. Clinical features
include recurrent skin infections (bacterial) as well as recurrent
fungal infections. The disease is usually detected by the age of 5 and is
diagnosed using the nitro-blue-tetrazolium (NBT) test, which remains
colourless due to NADPH deficiency (if NADPH is present the solution
turns blue). The patient will have a normal neutrophil count as there is
no defect in neutrophil production.

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9
Q
A Selective IgA deficiency disease
B Common variable immunodeficiency
C Nephrotic syndrome
D Bare lymphocyte syndrome
deficiency
E Sickle cell anaemia
F Chronic granulomatous
G Reticular dysgenesis
H Wiskott–Aldrich syndrome
I Interferon-gamma receptor

A 4-year-old boy is referred to a paediatrician after a period of mild but
chronic
diarrhoea. On examination the child is found to have icteric sclera and
hepatomegaly. Following blood tests, the doctor has a high suspicion that the
child could have a defect in MHC I.

A

D Bare lymphocyte syndrome

Bare lymphocyte syndrome (D) is caused by either deficiency in MHC I
(type 1; all T cells become CD4+ T cells) or MHC II (type 2; all T cells
become CD8+ T cells). Clinical manifestations include sclerosing cholangitis
with hepatomegaly and jaundice.

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10
Q
A Selective IgA deficiency disease
B Common variable immunodeficiency
C Nephrotic syndrome
D Bare lymphocyte syndrome
deficiency
E Sickle cell anaemia
F Chronic granulomatous
G Reticular dysgenesis
H Wiskott–Aldrich syndrome
I Interferon-gamma receptor

A 22-year-old woman visits her GP after several chest infections in the past few
years. As well as the chest infections, the patient reports that she has had several
bouts of diarrhoea over the same time period.

A

A Selective IgA deficiency disease

Selective IgA deficiency (A): IgA specifically provides mucosal immunity,
primarily to the respiratory and gastrointestinal systems. Selective
IgA deficiency results from a genetic inability to produce IgA and is
characterized by recurrent mild respiratory and gastrointestinal infections.
Patients with selective IgA deficiency are also at risk of anaphylaxis
to blood transfusions due to the presence of donor IgA. This
occurs especially after a second transfusion; antibodies having been
created against IgA during the primary transfusion. Selective IgA deficiency
is also linked to autoimmune diseases such as rheumatoid arthritis,
systemic lupus erythematosus and coeliac disease.

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11
Q
A HLA-matching
B Corticosteroids
C Cyclosporine A
D Azathioprine
E Sirolimus
F OKT3
G IL-2 receptor antibody
H Tacrolimus
I Anti-lymphocyte antibody

A 48-year-old man has undergone a kidney transplant operation as a result
of renal failure caused by long-standing diabetes mellitus. However, despite
immunosuppression,
signs of organ rejection become evident just 1 hour after
the procedure.

A

A HLA-matching

HLA-matching (tissue typing; A) is a preventative method of limiting
the risk of organ transplant rejection. It is impractical to match all HLA loci and hence tissue typing focuses on major HLA antigens such as
HLA-A and HLA-B. HLA-DR is also now routinely typed due to its role
in activating recipient’s T-helper cells. HLA-matching greatly reduces
the chance of hyperacute rejection caused by the presence of preformed
antibodies against the graft. Pre-formed antibodies may occur as
a result of previous blood transfusion or pregnancy.

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12
Q
A HLA-matching
B Corticosteroids
C Cyclosporine A
D Azathioprine
E Sirolimus
F OKT3
G IL-2 receptor antibody
H Tacrolimus
I Anti-lymphocyte antibody

A 45-year-old man undergoes a heart transplant due to end-stage heart failure.
Seventy-two hours after the operation, the patient shows signs of organ rejection
which is resistant to corticosteroid therapy. A mouse monoclonal antibody
is administered to save the transplant.

A

F OKT3

OKT3 (muromonab-CD3; F) is a mouse monoclonal antibody targeted
at the human CD3 molecule used to treat rejection episodes in patients
who have undergone allograft transplantation. Administration of the
antibody efficiently clears T cells from the recipient’s circulation, T cells
being the major mediator of acute organ rejection. Primary indications
include the acute corticosteroid-resistant rejection of renal, heart
and liver transplants. Anaphylaxis can result given a murine protein
is introduced to the recipient. OKT3 can also bind to CD3 on T cells,
stimulating the release of TNF-α and IFN-γ causing cytokine release
syndrome, which if severe, can be fatal.

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13
Q
A HLA-matching
B Corticosteroids
C Cyclosporine A
D Azathioprine
E Sirolimus
F OKT3
G IL-2 receptor antibody
H Tacrolimus
I Anti-lymphocyte antibody

A 32-year-old woman undergoes a bone marrow transplant for chronic lymphoblastic
leukaemia. She is prescribed a medication that inhibits calcineurin. On
examination, the patient has gum hyperplasia.

A

C Cyclosporine A

Cyclosporine A (C) is an important immunosuppressive agent in the organ
transplant arena, which inhibits the protein phosphatase calcineurin. This in
turn inhibits IL-2 secretion from T cells, a cytokine which stimulates T cell
proliferation. Another proposed mechanism of action involves the stimulation
of TGF-β production. TGF-β is a growth-inhibitory cytokine, the
production of T cells is reduced, hence minimizing organ rejection. Adverse
effects include nephrotoxicity, hepatotoxicity, diarrhoea and pancreatitis.
On examination, patients taking cyclosporine A may have gum hyperplasia.

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14
Q
A HLA-matching
B Corticosteroids
C Cyclosporine A
D Azathioprine
E Sirolimus
F OKT3
G IL-2 receptor antibody
H Tacrolimus
I Anti-lymphocyte antibody

A 62-year-old man who has undergone a kidney transplant was started on an
immunosuppressive agent prior to the operation. The patient is warned that he
will only be on the medication for a short period due to long-term side effects
such as osteoporosis.

A

B Corticosteroids

Corticosteroids (B) are used as an immunosuppressive agent in both the
prevention and treatment of transplant rejection. Corticosteroids inhibit
phospholipase A2 thereby blocking prostaglandin formation as well
as a series of inflammatory mediators. The immunosuppressive effects
of corticosteroids are numerous and include reducing the number of
circulating B cells, inhibiting monocyte trafficking, inhibiting T-cell
proliferation and reducing the expression of a number of cytokines, for
example, IL-1, IL-2 and TNF-α. Prednisolone is used prophylactically
before transplantation to prevent rejection; methylprednisolone is used
in the treatment of rejection. Side effects are frequent, however, and
include osteoporosis, diabetes mellitus and hypertension.

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15
Q
A HLA-matching
B Corticosteroids
C Cyclosporine A
D Azathioprine
E Sirolimus
F OKT3
G IL-2 receptor antibody
H Tacrolimus
I Anti-lymphocyte antibody

A 62-year-old man who is undergoing a liver transplant as a result of cirrhosis
is prescribed a medication that inhibits DNA synthesis in an attempt to prevent
proliferation of T cells.

A

D Azathioprine

Azathioprine (D) is an antimetabolite agent used in immunosuppressive
therapy. Azathioprine is metabolized into 6-mercaptopurine (6-MP), a
purine analogue that prevents DNA synthesis, thereby inhibiting the
proliferation of cells; lymphocytes are most affected. Antigen presenting
cells present non-self proteins (from the allograft) to T cells which
in turn produce IL-2 to stimulate T-cell proliferation. However, 6-MP
inhibits this proliferation and so the reaction between T cells and the
allograft is minimized. Important side effects include hepatotoxicity,
hypersensitivity reactions and myelosuppression.

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16
Q
A Anti-smooth muscle
B p-ANCA
C Anti-Jo1
D Anti-cyclic citrullinated protein
E Anti-centromere
F Anti-double stranded DNA
G Anti-parietal cell
H Anti-thyroid stimulating
hormone
I Anti-topoisomerase

A 56-year-old woman presents to the rheumatologist with pain in her hands.
On examination there are obvious deformities of her proximal interphalyngeal
joints and metacarpophalyngeal joints. Swan-neck deformities are seen but the
patient has retained functionality of her fingers.

A

D Anti-cyclic citrullinated protein

Anti-cyclic citrullinated protein (anti-CCP; D) antibody is associated
with rheumatoid arthritis. The antibody is directed at the filament
aggregating protein, filaggrin. Rheumatoid arthritis is a chronic systemic
autoimmune disease that results in a symmetrical deforming polyarthritis.
Clinical features include deformities of the hands (Boutonierre’s
deformity, swan-neck deformity, Z-thumb and ulnar deviation of the
fingers). The proximal interphalangeal joints are affected more than the
distal interphalangeal joints. Extra-articular manifestations include pulmonary
fibrosis, pericardial effusion, rheumatoid nodules and splenomegaly
(Felty’s syndrome). Rheumatoid factor is another antibody measured
in the investigation of rheumatoid arthritis, but is less sensitive
and specific in comparison to anti-CCP.

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17
Q
A Anti-smooth muscle
B p-ANCA
C Anti-Jo1
D Anti-cyclic citrullinated protein
E Anti-centromere
F Anti-double stranded DNA
G Anti-parietal cell
H Anti-thyroid stimulating
hormone
I Anti-topoisomerase

A 45-year-old woman is referred to a hepatologist after suffering an episode of
jaundice, fatigue and fever. Liver function tests reveal an increased AST. Biopsy
of the liver reveals cirrhosis and an autoimmune pathology is suspected.

A

A Anti-smooth muscle

Anti-smooth muscle (A) antibody (anti-SMA) suggests the diagnosis of
autoimmune hepatitis, but can also be present in patients with primary
sclerosing cholangitis. Autoimmune hepatitis is characterized by inflammation,
hepatocellular necrosis, fibrosis, with cirrhosis in severe cases.
Diagnosis requires histological confirmation together with the presence
of autoantibodies which may either be non-organ or liver-specific.
Autoimmune hepatitis is classified into two major groups depending on
the autoantibody present: type 1 is defined by the presence of anti-SMA
and/or anti-nuclear antibody, whilst type 2 is characterized by the presence
of anti-liver/kidney microsomal-1 antibody (anti-LKM-1).

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18
Q
A Anti-smooth muscle
B p-ANCA
C Anti-Jo1
D Anti-cyclic citrullinated protein
E Anti-centromere
F Anti-double stranded DNA
G Anti-parietal cell
H Anti-thyroid stimulating
hormone
I Anti-topoisomerase

A 42-year-old woman presents to the rheumatologist with weakness in her
proximal muscles and describes how she is finding it difficult to climb stairs.
On examination, a rash is observed surrounding both eyes. A high resolution CT
scan reveals a pulmonary fibrosis picture.

A

C Anti-Jo1

Anti-Jo1 (C) antibody is present in patients with dermatomyositis.
Dermatomyositis is characterized by autoimmune inflammation of muscle
fibres and skin. Clinical features include a heliotrope rash around
the eyes, Gottron’s papules on the dorsum of finger joints as well as weakness
of the proximal limb muscles which causes difficulty in
climbing stairs and rising from a chair. Dermatomyositis is commonly
associated with SLE and scleroderma. The presence of anti-Jo1 in dermatomyositis
typically suggests interstitial pulmonary involvement.
Blood tests reveal an increased ESR and raised creatine kinase level.

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19
Q
A Anti-smooth muscle
B p-ANCA
C Anti-Jo1
D Anti-cyclic citrullinated protein
E Anti-centromere
F Anti-double stranded DNA
G Anti-parietal cell
H Anti-thyroid stimulating
hormone
I Anti-topoisomerase

A 43-year-old man is referred to the rheumatologist after experiencing paleness
in his fingers, especially when exposed to cold weather. The patient also complains
of recent onset difficulty in swallowing solid food.

A

E Anti-centromere

Anti-centromere (E) antibody is associated with limited systemic scleroderma
(CREST syndrome). CREST syndrome is characterized by calcinosis,
Reynaud’s syndrome, oesophageal dysmotility, sclerodactyly and telangiectasia.
The pathophysiology is defined by endothelial injury and chronic
fibrosis (orchestrated by PDGF and TGF-β). Blood investigations will reveal
a raised ESR, anaemia and hypergammaglobulinaemia. Anti-centromere
antibodies detected in the presence of primary biliary cirrhosis indicate
portal hypertension.

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20
Q
A Anti-smooth muscle
B p-ANCA
C Anti-Jo1
D Anti-cyclic citrullinated protein
E Anti-centromere
F Anti-double stranded DNA
G Anti-parietal cell
H Anti-thyroid stimulating
hormone
I Anti-topoisomerase

A 42-year-old woman presents to the rheumatologist with joint pain and stiffness.
On examination, the patient appears to have a tight mouth and fine end
inspiratory crackles on auscultation of the lungs. The woman also has a widespread
itchy rash on her body.

A

I Anti-topoisomerase

Anti-topoisomerase (I) antibody is characteristic of diffuse systemic
scleroderma. Diffuse systemic scleroderma shares some features of limited
systemic scleroderma, however, it is more aggressive in its course,
affecting large areas of the skin as well as involving the kidneys, heart
and lungs. The pathogenesis of diffuse systemic scleroderma is similar
to that of limited systemic scleroderma. The presence of anti-topoisomerase
antibodies in diffuse systemic sclerosis is associated with
pulmonary
interstitial fibrosis.

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21
Q
A Anti-mitochondrial
B c-ANCA
C Anti-cardiolipin
D Anti-ribonucleoprotein
E Anti-glutamic acid decarboxylase
F Anti-Ro
G Anti-nuclear
H Anti-intrinsic factor
I Anti-endomysial

A 25-year-old woman presents to her GP with a dry mouth and eyes for a period
of 2 weeks. The patient also complains of joint pains over this time-course.

A

F Anti-Ro

Anti-Ro (anti-SS-A; F) and Anti-La (anti-SS-B) antibodies are present in
approximately 50 per cent of patients with Sjögren’s syndrome, as well
as a lower proportion of patients with systemic lupus erythematosus.
Sjögren’s syndrome is characterized by the destruction of the epithelial
cells of exocrine glands. Salivary gland biopsy reveals an infiltrate of
T and B cells; CD4+ T cells are most prominent. Clinical features include dryness of the eyes (confirmed by Schirmer’s test) and mouth, parotid
swelling, fatigue, arthralgia and myalgia. Blood tests will demonstrate a
raised ESR and occasionally a mild anaemia.

22
Q
A Anti-mitochondrial
B c-ANCA
C Anti-cardiolipin
D Anti-ribonucleoprotein
E Anti-glutamic acid decarboxylase
F Anti-Ro
G Anti-nuclear
H Anti-intrinsic factor
I Anti-endomysial

A 52-year-old man is referred to a gastroenterologist with itchy skin and
malaise. On examination, the man has bruising on his arms and legs.

A

A Anti-mitochondrial

Anti-mitochondrial (A) antibodies are associated with primary biliary
cirrhosis (PBC), and are immunoglobulins against mitochondria in cells
of the liver. PBC is an autoimmune disease of unknown cause characterized
by lymphocytic destruction of the bile canaliculi of the liver;
build-up of bile leads to fibrosis and eventually cirrhosis. Clinical features
include pruritis (increased bile acids in circulation) as well as the
effects of reduced absorption of fat soluble vitamins (vitamin D, osteomalacia;
vitamin K, bruising; vitamin A, blindness).

23
Q
A Anti-mitochondrial
B c-ANCA
C Anti-cardiolipin
D Anti-ribonucleoprotein
E Anti-glutamic acid decarboxylase
F Anti-Ro
G Anti-nuclear
H Anti-intrinsic factor
I Anti-endomysial

A 10-year-old girl is brought to see a GP. Her mother describes how she has
recently been urinating with greater frequency than previously as well as feeling
thirsty and has lost several kilograms in weight in the recent weeks.

A

E Anti-glutamic acid decarboxylase

Anti-glutamic acid decarboxylase (anti-GAD; E) antibody is present
in patients with type 1 diabetes mellitus (T1DM). The pathogenesis of
T1DM involves the autoimmune destruction of β-cells in the islets of
Langerhans in the pancreas. β-Cells are the primary storage site for
insulin in the body, and so destruction of these cells leads to diminished
insulin release and hyperglycaemia. GAD is an enzyme responsible for
the conversion of glutamate to GABA; GABA is the neurotransmitter
involved in the release of insulin from β-cells. Presenting features of
T1DM include polyuria, polydipsia and weight loss.

24
Q
A Anti-mitochondrial
B c-ANCA
C Anti-cardiolipin
D Anti-ribonucleoprotein
E Anti-glutamic acid decarboxylase
F Anti-Ro
G Anti-nuclear
H Anti-intrinsic factor
I Anti-endomysial

A 42-year-old man presents to accident and emergency with haemoptysis. The
patient also describes how he has been experiencing nose bleeds with increasing
frequency in recent weeks. The patient is noted to have a saddle-shaped nose.

A

B c-ANCA

c-ANCA (cytoplasmic anti-neutrophil cytoplasmic antibodies; B) are
common in patients with Wegener’s granulamatosis, a vasculitic disease
that is in severe cases life threatening. c-ANCA is directed towards proteinase
3 (PR3) within the neutrophil cytoplasm. Wegner’s granulamatosis
primarily affects the nose (saddle-nose deformity due to perforated
septum; epistaxis), lungs (pulmonary haemorrhage) and kidneys (glomerulonephritis).
Due to its fulminant course, patients require life-long
immunosuppression, usually with corticosteroids.

25
Q
A Anti-mitochondrial
B c-ANCA
C Anti-cardiolipin
D Anti-ribonucleoprotein
E Anti-glutamic acid decarboxylase
F Anti-Ro
G Anti-nuclear
H Anti-intrinsic factor
I Anti-endomysial

A 22-year-old woman presents to her GP with recent onset diarrhoea and
abdominal cramping after she has eaten meals containing wheat.

A

I Anti-endomysial

Anti-endomysium (I) is characteristic of coeliac disease, autoimmune
disease of the small intestine that results from an immune reaction to
gliadin (peptide found in wheat, barley and rye). The endomysium is in
fact related to muscle fibres; although muscle fibres are not affected in
coeliac disease, anti-endomysial antibodies are useful in the diagnosis
of coeliac disease. Clinical features include diarrhoea, abdominal pain
and mouth ulcers. Other autoantibodies that are used in the diagnosis
of coeliac disease are anti-tissue transglutaminase antibody and antigliadin
antibodies.

26
Q
A TSH receptor
B Nuts
C DNA
D Nickel
E Type IV collagen
F Chlamydia trachomatis
G Mouldy hay
H Grass pollen
I Pancreatic β-cell proteins

An 11-year-old girl presents to the GP with increased thirst and urinary frequency.
Urine dipstick demonstrates the presence of glucose.

A

I Pancreatic β-cell proteins

Pancreatic β-cell proteins (I) are the antigenic target for cytotoxic CD8+
T cells in type 1 diabetes mellitus (T1DM). T1DM is a type IV hypersensitivity
reaction since it is T-cell mediated; the pathogenesis involves
the destruction of β-cells in the islets of Langerhans in the pancreas by
CD8+ T cells. β-cells are the storage site for insulin in the body, and so
destruction of these cells leads to diminished insulin release and hyperglycaemia.
Presenting features of T1DM include polyuria, polydipsia and
weight loss. Antibodies to glutamate decarboxylase (GAD) as well as
islet cells may also circulate in T1DM patients.

27
Q
A TSH receptor
B Nuts
C DNA
D Nickel
E Type IV collagen
F Chlamydia trachomatis
G Mouldy hay
H Grass pollen
I Pancreatic β-cell proteins

A 13-year-old girl eats a slice of cake at a birthday party and quickly develops
swollen lips, itchy skin and difficulty breathing. A shot of intramuscular adrenaline
is immediately administered.

A

B Nuts

Ingestion of nuts (B) can lead to a type I hypersensitivity, characterized
by a strong CD4+ Th2 response which causes release of IL-4 and IL-13.
This causes B cells to produce IgE, which in turn binds to Fc receptors
on mast cells. On re-exposure to the allergen the IgE on mast cells
cross-links, with resultant mast cell degranulation (release of histamine
and tryptases) and arachidonic acid metabolism (producing leukotrienes
and prostaglandins). Clinical features include erythema, rhinitis, urticaria,
angio-oedema, bronchoconstriction and in severe cases anaphylactic
shock.

28
Q
A TSH receptor
B Nuts
C DNA
D Nickel
E Type IV collagen
F Chlamydia trachomatis
G Mouldy hay
H Grass pollen
I Pancreatic β-cell proteins

A 56-year-old farmer presents to his GP with a 2-month history of worsening
shortness of breath. He mentions that he has experienced periodic fevers,
malaise and mild shortness of breath, which has recently become so bad that he
has had to stop work.

A

G Mouldy hay

Chronic exposure to mouldy hay (G) is the cause of farmer’s lung, an
example of an extrinsic allergic alveolitis. Actinomycetes are the most
common pathogen found in hay dust, which are subsequently inhaled.
Inhalation over prolonged periods of time leads to immune complex
formation as antibodies combine with the inhaled allergen (type III
hypersensitivity reaction); the immune complexes are deposited in the
walls of the alveoli. Chronic exposure leads to pulmonary fibrosis, with
associated shortness of breath, cyanosis and cor pulmonale.

29
Q
A TSH receptor
B Nuts
C DNA
D Nickel
E Type IV collagen
F Chlamydia trachomatis
G Mouldy hay
H Grass pollen
I Pancreatic β-cell proteins

A 45-year-old man presents to accident and emergency with a sudden onset of
haemoptysis. His wife mentions that the patient had noticed some blood in his
urine a few days previously but had thought nothing of it.

A

E Type IV collagen

Type IV collagen (E), is the target of soluble IgG in Goodpasture’s disease
(type II hypersensitivity reaction). Type IV collagen is present in
the glomerular basement membrane and lung basement membrane.
Pulmonary features include cough, dyspnoea and haemoptysis; renal
features include haematuria, acute renal failure and nephrotic syndrome.
Investigations reveal the presence of anti-type IV collagen antibodies in the circulation; immunofluorescence will show linear deposition of IgG
along the glomerular basement membrane.

30
Q
A TSH receptor
B Nuts
C DNA
D Nickel
E Type IV collagen
F Chlamydia trachomatis
G Mouldy hay
H Grass pollen
I Pancreatic β-cell proteins

A 12-year-old boy experiences a runny nose, itchiness of his eyes and nasal
congestion. His GP suggests he has a seasonal condition, and should begin taking
anti-histamines to help relieve him of his symptoms.

A

H Grass pollen

Grass pollen (H) may cause allergic rhinitis via a type I hypersensitivity
reaction. The allergen triggers IgE production, which bind to the cell
surface of mast cells and basophils. On repeated exposure to pollen, the
mast cells degranulate, releasing histamine as well as other mediators.
This results in the characteristic features of allergic rhinitis such as a
runny nose, sneezing, itchiness, watery eyes and nasal congestion.

31
Q
A Stony fruit
B HBsAg
C Myelin basic protein
D Rhesus antigens
E Glycoprotein IIb–IIIa
F Peanuts
G Antiserum
H Synovial membrane antigens
I Poison ivy

A 26-year-old woman at a work dinner has ordered a curry. Soon after eating
the meal, she feels short of breath and wheezy. Her husband who is present
swiftly administers an intramuscular shot of adrenaline.

A

F Peanuts

Allergy to peanuts (F) causes a spectrum of clinical manifestations, from
mild food allergy to severe anaphylaxis. The underlying pathogenesis is
the binding of the allergen to IgE causing mast cell degranulation and histamine
release (a potent vasodilator and bronchoconstrictor). In anaphylaxis,
this release of histamine occurs throughout the body, leading to the
clinical features of shortness of breath, wheeze, swollen lips and signs of
shock. Anaphylaxis is a medical emergency and requires prompt administration
of intramuscular adrenaline and urgent transfer to a hospital.

32
Q
A Stony fruit
B HBsAg
C Myelin basic protein
D Rhesus antigens
E Glycoprotein IIb–IIIa
F Peanuts
G Antiserum
H Synovial membrane antigens
I Poison ivy

A 35-year-old woman presents to the GP with blurry vision and weakness in
her legs. Cerebrospinal fluid demonstrates oligoclonal bands of IgG on
electrophoresis.

A

C Myelin basic protein

Myelin basic protein (C) and proteolipid protein are oligodendrocyte
proteins implicated in the pathogenesis of multiple sclerosis. Multiple
sclerosis (MS) is a demyelinating disease in which the myelin sheaths
surrounding neurons of the brain and spinal cord are destroyed.
Associated with the disease process is the antigenic stimulation of CD4+
T cells which in turn activate CD8+ cytotoxic T cells and macrophages;
these are directed at oligodendrocyte proteins (type IV hypersensitivity
reaction) causing destruction of oligodendrocytes and myelin. Clinical
features of MS include optic neuritis, urinary/bowel incontinence, weakness
of the arms/legs and dysphagia.

33
Q
A Stony fruit
B HBsAg
C Myelin basic protein
D Rhesus antigens
E Glycoprotein IIb–IIIa
F Peanuts
G Antiserum
H Synovial membrane antigens
I Poison ivy

A 34-year-old man who has been taking amoxicillin for pneumonia has developed
tiredness and palpitations since taking the medication. Blood tests reveal a
normocytic anaemia and direct antiglobulin test is positive.

A

D Rhesus antigens

Rhesus antigens (D) are found on the surface of erythrocytes. The rhesus
(Rh) blood group system is clinically the most important after the ABO
system; the most commonly used Rh antigen is the D antigen, signifying
whether a patient is Rh positive or negative. Antibodies directed
against the Rh antigen results in autoimmune haemolytic anaemia
(AIHA; type II hypersensitivity reaction). Most commonly the cause is
idiopathic, however, chronic lymphocytic leukaemia, systemic lupus
erythematosus and drugs (methyldopa and penicillin) can trigger AIHA.
Direct antiglobulin test is positive.

34
Q
A Stony fruit
B HBsAg
C Myelin basic protein
D Rhesus antigens
E Glycoprotein IIb–IIIa
F Peanuts
G Antiserum
H Synovial membrane antigens
I Poison ivy

A 34-year-old man, who is a known intravenous drug user, presents to accident
and emergency with a 1-week history of fever, fatigue and abdominal pain. The
patient also has associated joint pain. An angiogram reveals the presence of
multiple aneurysms.

A

B HBsAg

HBsAg (B) may be associated with the development of polyarteritis
nodosa (PAN), a vasculitis of small and medium sized vessels. Immune
complexes (type III hypersensitivity reaction) are deposited within such
vessels leading to fibrinoid necrosis and neutrophil infiltration; as a
result the vessel walls weaken and there is aneurysm development.
Investigations will reveal a raised ESR, CRP and immunoglobulin level.
pANCA is also associated with PAN. Angiogram will reveal multiple
aneurysms. Corticosteroids and cytotoxic agents are required to control
disease progression.

35
Q
A Stony fruit
B HBsAg
C Myelin basic protein
D Rhesus antigens
E Glycoprotein IIb–IIIa
F Peanuts
G Antiserum
H Synovial membrane antigens
I Poison ivy

A 45-year-old man with diagnosed systemic lupus erythematosus (SLE) presents
to the GP with a recent onset of nose bleeds and bleeding of his gums when he
brushes his teeth. Blood tests reveal a very low platelet count.

A

E Glycoprotein IIb–IIIa

Glycoprotein IIb–IIIa (E) on the surface of platelets is the target for
IgG autoantibodies (type II hypersensitivity reaction) in autoimmune
thrombocytopenic purpura (AITP). IgG directed at platelets makes them
more susceptible to destruction by splenic macrophages and as a result
the platelet count in affected individuals will be very low. Symptoms
depend upon the platelet count:

36
Q
A Cyclophosphamide
B Mycophenolate mofetil
C Basiliximab
D Abatacept
E Rituximab
F Efalizumab
G Infliximab
H Ustekinumab
I Denosumab

A 46-year-old man with long-standing SLE is seen by his rheumatologist. He
had previously been treated with corticosteroids, but has now developed endorgan
involvement of his kidneys, lungs and heart.

A

A Cyclophosphamide

Cyclophosphamide (A) is an alkylating agent, attaching an alkyl
group to the guanine base of DNA. This causes damage to the DNA
structure and therefore prevents cell replication; cyclophosphamide
affects B-cell replication more than T cells. Indications include multisystem
connective tissue disease and vasculitis such as systemic
lupus erythematosus and Wegner’s granulomatosis. Cyclophosphamide
also has a role in treating cancers such as leukaemia and lymphoma.
Complications of therapy include bone marrow suppression, hair loss
and it has carcinogenic properties which may cause transitional cell
carcinoma of the bladder.

37
Q
A Cyclophosphamide
B Mycophenolate mofetil
C Basiliximab
D Abatacept
E Rituximab
F Efalizumab
G Infliximab
H Ustekinumab
I Denosumab

A 56-year-old woman is seen in the rheumatology outpatient clinic. She has
long-standing rheumatoid arthritis, which despite treatment with methotrexate
has become more severe. The rheumatologist decides that a CTL4-
immunoglobulin fusion protein may help.

A

D Abatacept

Abatacept (D) is a CTLA4–immunoglobulin fusion protein indicated in
the treatment of rheumatoid arthritis (disease which has been resistant
to treatment with disease modifying drugs). Abatacept prevents antigen
presenting cells from delivering a co-stimulatory signal to T cells in
order to activate them; this is achieved by abatacept binding with high
affinity to the B7 protein (CD80 and CD86) on the cell surface of APCs.
Side effects include increased risk of infection from TB, hepatitis B virus
and hepatitis C virus.

38
Q
A Cyclophosphamide
B Mycophenolate mofetil
C Basiliximab
D Abatacept
E Rituximab
F Efalizumab
G Infliximab
H Ustekinumab
I Denosumab

A 56-year-old man who is undergoing kidney transplant surgery is given medication
to prevent allograft rejection. The drug prevents guanine synthesis to
induce immunosuppression.

A

B Mycophenolate mofetil

Mycophenolate mofetil (B) is the prodrug of mycophenolic acid which
inhibits inosine monophosphate dehydrogenase (IMPDH), an enzyme
required in guanine synthesis; impaired guanine synthesis reduces the
proliferation of both T and B cells, but T cells are affected to a greater
extent. Mycophenolate mofetil is indicated as an immunosuppressive
agent in transplant patients as well as an alternative to cyclophosphamide
in the treatment of autoimmune diseases and vasculitides. Side
effects include bone marrow suppression (particularly low white blood
cells and platelets) as well as herpes virus reactivation.

39
Q
A Cyclophosphamide
B Mycophenolate mofetil
C Basiliximab
D Abatacept
E Rituximab
F Efalizumab
G Infliximab
H Ustekinumab
I Denosumab

A 58-year-old woman who suffers from rheumatoid arthritis is seen by her
rheumatologist. She has been taking long-term disease modifying anti-rheumatic
drugs, but her condition has recently worsened. As a result the
doctor
prescribes a TNF-α inhibitor.

A

G Infliximab

Infliximab (G) is a TNF-α antagonist used in the treatment of rheumatoid
arthritis, ankylosing spondylitis, Crohn’s disease and psoriasis.
Infliximab has a high affinity for TNF-α but does not bind to TNF-β.
TNF-α has the physiological role of inducing pro-inflammatory
cytokines as well as promoting leukocyte migration and endothelial
adhesion. Toxicity may result in reduced protection against infection
from TB, hepatitis B virus and hepatitis C virus, a lupus-like condition,
demyelination and malignancy.

40
Q
A Cyclophosphamide
B Mycophenolate mofetil
C Basiliximab
D Abatacept
E Rituximab
F Efalizumab
G Infliximab
H Ustekinumab
I Denosumab

A 56 year old with known systemic lupus erythematosus has been treated with
long-term steroids. The patient presents to a rheumatologist with back pain and
a DEXA scan confirms osteoporosis

A

I Denosumab

Denosumab (I) is an antibody directed towards the RANK ligand in
bones. Osteoblasts are responsible for bone formation, whilst osteoclasts
(which contain the cell surface receptor RANK) break down
bone. Inhibition of RANK by denosumab therefore inhibits osteoclast function
and differentiation, thereby preventing the breakdown of bone.
Denosumab is indicated in the treatment of osteoporosis but is also used
in the management of multiple myeloma and bone metastases. Toxicity
can predispose to respiratory and urinary tract infections.

41
Q
A Minimal change disease
B Wegener’s granulomatosis
C Microscopic polyangitis
D Lupus nephritis
E IgA nephropathy
F Membranoproliferative
glomerulonephritis
G Rapidly progressive
glomerulonephritis
H Post-streptococcal
glomerulonephritis
I Goodpasture’s syndrome

A 50-year-old woman presents to accident and emergency with haematuria.
Blood tests demonstrate deranged renal function and further tests reveal the
presence of circulating cANCA antibodies. The patient is noted to have a saddleshaped
nose.

A

B Wegener’s granulomatosis

Wegener’s granulamatosis (B) is a systemic vasculitis characterized clinically
by epistaxis, haemoptysis and haematuria. Wegener’s granulomatosis
is defined by the presence of cytoplasmic anti-neutrophil cytoplasmic
antibodies (cANCA). c-ANCA is directed towards proteinase 3 (PR3),
an enzyme normally present within the cytoplasm of neutrophils. It is
proposed that an infection is the trigger for the disease, which causes
circulating neutrophils to become adherent to the endothelium and
upregulation of PR3 on the cell surface. Vasculitis is mediated by both
direct effect of PR3 on the endothelium as well as cANCA–PR3 immune
complex deposition.

42
Q
A Minimal change disease
B Wegener’s granulomatosis
C Microscopic polyangitis
D Lupus nephritis
E IgA nephropathy
F Membranoproliferative
glomerulonephritis
G Rapidly progressive
glomerulonephritis
H Post-streptococcal
glomerulonephritis
I Goodpasture’s syndrome

A 24-year-old man presents to his GP with a few days’ history of blood in his
urine. Urinary investigations reveal the presence of proteinuria, red and white
cell casts and dysmorphic red cells. The patient’s notes state that he was diagnosed
with pharyngitis in the previous week. Blood tests reveal a raised IgA
level.

A

E IgA nephropathy

IgA nephropathy (Berger’s disease; E) is the most common cause of
glomerunephritis in the developed world. The condition occurs after a
gastrointestinal or upper respiratory infection; potential offenders are
postulated to include Haemophilus influenzae, hepatitis B virus and
cytomegalovirus. Antigenic targets for IgA are thought to include collagen,
fibronectin and laminin. Characteristically there is mesangial
proliferation with deposition of IgA together with alternative pathway
factors C3 and properdin. Blood tests will reveal a raised IgA level.
Henoch–Schonlein purpura has a similar pathogenesis to IgA nephropathy
but presents in children and has extra-renal clinical features.

43
Q
A Minimal change disease
B Wegener’s granulomatosis
C Microscopic polyangitis
D Lupus nephritis
E IgA nephropathy
F Membranoproliferative
glomerulonephritis
G Rapidly progressive
glomerulonephritis
H Post-streptococcal
glomerulonephritis
I Goodpasture’s syndrome

A 25-year-old man presents to his GP with symptoms and signs of nephritic
syndrome. The patient had a sore throat 2 weeks previously. Blood tests reveal
anti-streptolysin titre is high, while IgA levels are normal.

A

H Post-streptococcal
glomerulonephritis

Post-streptococcal glomerulonephritis (H) is usually caused by a preceding
group A β haemolytic streptococcus pharyngitis. Anti-streptolysin O
titre (ASOT) will be raised. Pathological hallmarks of post-streptococcal glomerulonephritis include diffuse hypercellularity and diffuse swelling
of the mesangium and glomerular capillaries. Influx of neutrophils
and macrophages may reveal crescent formation on histology. Direct
immunofluorescence
reveals the sub-epithelial deposition of IgG and C3.
The condition usually subsides with supportive treatment, including
antibiotic therapy to combat the outstanding infection.

44
Q
A Minimal change disease
B Wegener’s granulomatosis
C Microscopic polyangitis
D Lupus nephritis
E IgA nephropathy
F Membranoproliferative
glomerulonephritis
G Rapidly progressive
glomerulonephritis
H Post-streptococcal
glomerulonephritis
I Goodpasture’s syndrome

A 65-year-old man with known renal failure is transferred to the renal team by
the accident and emergency department with worsening renal function. A renal
biopsy is taken which demonstrates the presence of crescents on histology;
immunofluorescence staining of IgG/C3 reveals a granular pattern. The man is
very ill with suggestions that he may require a renal transplant.

A

G Rapidly progressive
glomerulonephritis

Rapidly progressive glomerulonephritis (RPGN; G) is the most aggressive
of all glomerulonephritides, which may cause end-stage renal failure
over a period of days. The three sub-types include immune complex
disease, pauci-immune disease and anti-glomerular basement membrane
disease, all of which demonstrate crescent formation on biopsy (proliferation
of macrophages and parietal epithelial cells). Immunofluoresence
of IgG/C3 distinguishes between the three sub-types: immune complex
disease is characterized by granular staining, pauci-immune disease
shows absent/scant staining, while anti-glomerular basement membrane
disease demonstrates linear staining.

45
Q
A Minimal change disease
B Wegener’s granulomatosis
C Microscopic polyangitis
D Lupus nephritis
E IgA nephropathy
F Membranoproliferative
glomerulonephritis
G Rapidly progressive
glomerulonephritis
H Post-streptococcal
glomerulonephritis
I Goodpasture’s syndrome

A 3-year-old boy is seen by the GP after his mother noticed swelling of his legs.
A week previously the boy had been stung by a bee. Urine dipstick reveals the
presence of proteinuria, while blood tests show hypoalbuminaemia and hyperlipidaemia.

A

A Minimal change disease

Minimal change disease (A) is the most common cause of nephrotic
syndrome in children. Triggers include a recent allergic reaction such as
a bee sting (type I hypersensitivity reaction). Histological characteristics
of renal biopsy specimens include a lack of structural change visible on
light microscopy, while electron microscopy will demonstrate podocyte
effacement. Steroids are the primary treatment modality, which lead to
remission of disease in the vast majority of cases.

46
Q
A Histocompatibility testing
B Immunofluorescence
C Latex fixation test
D Radioallergosorbent test
E Patch testing
F Kveim test
G Skin prick test
H Western blot
I Direct antiglobulin test

A 39-year-old homosexual man presents to accident and emergency with shortness
of breath and a dry cough. A chest X-ray shows widespread pulmonary
opacification. PCR confirms the diagnosis of Pneumocystis pneumoniae infection.
A test is ordered to confirm the underlying diagnosis

A

H Western blot

Western blot (H) is a technique used to detect specific proteins in a
patient’s serum; it is used in the confirmatory HIV test to detect specific
antibodies to HIV. The first step is to separate native proteins by gel
electrophoresis. The proteins are subsequently transferred to a membrane
on which specific antibodies present in the serum may bind to
HIV proteins produced using recombinant DNA. Unbound antibodies are
washed away. Enzyme-linked antibodies are then added; these determine
to which protein the subject has antibodies.

47
Q
A Histocompatibility testing
B Immunofluorescence
C Latex fixation test
D Radioallergosorbent test
E Patch testing
F Kveim test
G Skin prick test
H Western blot
I Direct antiglobulin test

A 45-year-old man presents to accident and emergency with worsening shortness
of breath. Examination findings are consistent with pulmonary fibrosis.
Chest X-ray demonstrates the presence of bihilar lymphadenopathy. Erythema
nodosum is observed on the patient’s shins.

A

F Kveim test

Kveim test (F) is an investigation used to diagnose sarcoidosis. A sample
of spleen from a patient with known sarcoid is injected intradermally
into a suspected patient. A positive test is evidenced by the presence of
non-caseating granuloma formation on biopsy of the site, 4–6 weeks
after the initial injection. Although not used in the UK due to infection
concerns (especially bovine spongiform encephalopathy), it is still available
in many countries.

48
Q
A Histocompatibility testing
B Immunofluorescence
C Latex fixation test
D Radioallergosorbent test
E Patch testing
F Kveim test
G Skin prick test
H Western blot
I Direct antiglobulin test

A 50-year-old man with known SLE develops jaundice. On examination he is
found to have conjunctival pallor and is short of breath. Blood tests reveal an
elevated unconjugated bilirubin level.

A

I Direct antiglobulin test

Direct antiglobulin test (DAT; I) also known as direct Coombs test, is
the investigation of choice for the diagnosis of autoimmune haemolytic
anaemia (AIHA). Causes of AIHA include lymphoproliferative disorders,
drugs (penicillin) and autoimmune diseases (SLE). The test involves the
separation of RBCs from the serum which is subsequently incubated
with anti-human globulin. In the case of AIHA, the anti-human globulin
will agglutinate the RBCs, which is visualized as clumping of the
cells.

49
Q
A Histocompatibility testing
B Immunofluorescence
C Latex fixation test
D Radioallergosorbent test
E Patch testing
F Kveim test
G Skin prick test
H Western blot
I Direct antiglobulin test

A 12-year-old girl is referred to a paediatrician after suffering with allergies to
a number of foods including peanuts and eggs. Her mother wants to check if
she is allergic to any other foods, inhalants or specific materials, so that she can
be prevented from coming into contact with potential allergens.

A

G Skin prick test

Skin prick test (G) is the gold standard for investigating such type I
hypersensitivity reactions. The test involves a few drops of purified
allergen being pricked onto the skin. Allergens which are tested for
include foods, dust mites, pollen and dust. A positive test is indicated by
wheal formation, caused by cross-linking of IgE on the mast cell surface
leading to histamine release.

50
Q
A Histocompatibility testing
B Immunofluorescence
C Latex fixation test
D Radioallergosorbent test
E Patch testing
F Kveim test
G Skin prick test
H Western blot
I Direct antiglobulin test

A 5-year-old boy presents to accident and emergency with purpura on his legs
and buttocks, joint pain and abdominal pain. The boy’s mother states that the
child had suffered from a sore throat approximately 1 week previously. The doctor
would like to perform an investigation to make sure of the diagnosis.

A

B Immunofluorescence

Immunofluorescence (B) is an immunological technique used in conjunction
with fluorescence microscope. Fluorophores (fluorescent
chemical compounds) attached to specific antibodies are directed at
antigens found within a biological specimen, most commonly a biopsy
sample, to visualize patterns of staining. For example, in Henoch–
Schönlein purpura, anti-IgA antibody will demonstrate IgA deposits in
the capillary walls of the specimen. Immunofluorescence may be direct
(use of a single antibody bound to a single fluorophore) or indirect
(secondary antibody carrying the fluorophore binds to the primary
antibody).