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Path > Meeran Immuno > Flashcards

Meeran Immuno Flashcards

1
Q

What is severe combined immunodeficiency (SCID)?

A

Defects in T cells and B cells with hypoplasia and atrophy of the thymus and mucosa-associated lymphoid tissue

Two subtypes:
* X-linked - mutation of IL2 receptor
* Autosomal recessive - mutation of adenosine deaminase gene

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2
Q

What is Kostmann syndrome?

A

Severe congenital neutropenia as a result of neutrophil maturation failure (<500/uL)

Nitro-blue-tetrazolium test is normal (differentiates it from chronic glomerulomatous disease)

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3
Q

What is Bruton’s agammaglobulinaemia?

A

X-linked disease which is caused by a mutation of the BTK gene. This inhibits B-cell maturation and therefore B-cell and immunoglobulin levels are diminished. T cells will be normal.

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4
Q

What is protein-losing enteropathy?

A

There is severe loss of protein via the GIT due to mucosal disease, lymphatic obstruction and cell death which lead to incfrased permeability of proteins.

Hypoproteinaemia can result and this leads to fewer immunoglobulins being produced so a decrease in adaptive immune response

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5
Q

What is Di George’s syndrome?

A

22q11 deletion (aka CATCH syndrome):
Cardiac abnormalities
Atresia (oesophageal)
Thymic aplasia - leads to deficieny in T cells
Cleft palate
Hypocalcaemia

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6
Q

What is Wiskott-Aldrich syndrome?

A

X-linked condition with a mutation in the WASp gene - leads to development of lymphomas, thrmbocytopenia and eczema

Clinical features: easy bruising, nose bleeds, GI bleeds, recurrent bacterial infections

Bloods: low IgM, high IgA and IgE. IgG levels are variable

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7
Q

What is common variable immunodeficieny (CVID)?

A

Mutation in MHC III which causes abherrant class switching, with an increased risk of lymphoma and granulomas.

Patients are predisposed to developing autoimmune diseases + H. Influenzae and Strep. Pneumoniae infections

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

What is chronic granulomatous disease?

A

X-linked disorder causing deficiency of NADPH oxidase - neutrophils are unable to clear pathogens, but neutrophil count is normal. There is chronic inflammation with non-caseating granulomas

Clinical features include recurrent skin infections (bacterial) as well as recurrent fungal infections.

Nitro-blue-tetrazolium test is negative (due to NADPH deficiency).

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9
Q

What is bare lymphocyte syndrome?

A

Two types:
* Type 1 - deficiency in MHC I (T cells becomes CD4+)
* Type 2 - deficiency in MHC II (T cells become CD8+)

Clinical manifestations: sclerosing cholangitis, hepatomegaly and jaundice

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10
Q

What is selective IgA deficiency?

A

IgA provides mucosal immunity in the respiratory and GI systems

If this is deficient, you get mild respiratory and GI infections + these patients are at risk of anaphylaxis during blood transfusions (due to presence of donor IgA). This occurs especially after a second transfusion; antibodies having been created against IgA during the primary transfusion.

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11
Q

What is OKT3?

A

Muromonab-CD3 is a mouse monoclonal antibody which targets CD3 molecules in rejection episodes of allograft transplantation.

It clears T cells from the recipient’s circulation (which are major mediators of acute organ rejection)

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12
Q

What is cyclosporine?

A

Immunosuppressive agent which inhibits phosphatase calcineurin. This then inhibits IL2 (stimulatory) from T cells and stimulates TGF-beta (inhibitory)

Patients taking this can have gum hyperplasia, nephrotoxicity, hepatotoxicity, diarrhoea and pancreatitis

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13
Q

What is azathioprine?

A

Antimetabolite agent used in immunosuppresive therapy.

It prevents DNA synthesis and thereby inhibits proliferation of cells –> reduced presentation of antigens from allografts so there is no immune rejection

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14
Q

What condition is associated with anti-smooth muscle antibodies?

A

Autoimmune hepatitis - inflammation, hepatocellular necrosis, fibrosis and cirrhosis

*Also seen in primary sclerosing cholangitis

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15
Q

What conidition is anti-Jo1 associated with?

A

Dermatomyositis - heliotrope rash around the eye, Gottron’s papules on the dorsum of finger joints, proximal limb muscle weakness

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16
Q

What is anti-topoisomerase (Scl-70) antibody associated with?

A

Diffuse systemic scleroderma

Similar to limited scleroderma but is more aggressive affectng the kidneys, lungs and heart.

You also see pulmonary interstitial fibrosis

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17
Q

How does Sjögren’s syndrome present and what antibodies are associated with it?

A

It is the destruction of epithelial cells of exocrine glands - dry eyes and mouth, parotid swelling, arthralgia and myalgia

Associated with anti-Ro and anti-La antibodies

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18
Q

What is anti-glutamic acid decarboxylase (GAD) associated with?

A

Type 1 diabetes where there is autoimmune destruction of beta-cells in the islets of Langerhans of the pancreas due to antigenic target for cytotoxic CD8+ T cells

GAD is responsible for the conversion of glutamate to GABA. GABA is involved in the release of insulin from beta-cells

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19
Q

How does Wegener’s granulamatosis (granulamatosis with polyangiitis) present?

A

It is a vasculitic condition primarily affecting the nose, lungs and kidneys:

Saddle-nose deformity (performated septum –> epitaxis)
Pulmonary haemorrhage
Glomerulonephritis

*Patients will require life-long immunosuppression

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20
Q

What is the main target of IgG in Goodpasture’s disease?

A

Type IV collagen

*THis is a type 2 hypersensitivity reaction

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21
Q

What type of hypersensitivity reaction can Chlamydia trachomatis cause?

A

Type III hypersensitivity reaction causing reactive arthritis - autoimmune with negative synovial fluid cultures

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22
Q

What type of hypersensitivity reaction causes Grave’s disease?

A

Type 2 hypersensitivity reaction caused by anti-TSH antibodies

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23
Q

What type of hypersensitivity reaction is contact dermatitis?

A

Type 4 - it occurs when Nickel (hapten) binds with skin proteins. These are then detected by Langerhan’s antigen presenting cells.

24
Q

What is the pathophysiology of multiple sclerosis?

A

Antigenic stimulation of CD4+ T cells which activate CD8+ cytotoxic T cells and macrophages –> target oligodendrocyte proteins (myelin basic protein and proteolipid protein). This is a type 4 hypersensitivity reaction

25
Q

What is the pathophysiology behind hepatitis B infection and development of polyarteritis nodosa?

A

This is a type 3 hypersensitivity reaction where immune complexes formed after exposure to HBsAg cause fibrinoid necrosis and neutrophil infiltration –> vasculitis of small and medium sized vessels (weak walls and aneurysm development)

26
Q

Want to know more about immune-based therapies?

A

Page 169 of meeran’s path book

27
Q

How do you differentiate IgA nephropathy (Berger’s disease) from post-streptococcal glomerulonephritis?

A

IgA nephropathy is more acute around 3-4 days after GI or respiratory infection. Common infectious agents include H. influenzae, HBV, CMV. You also get a raised IgA level.

In post-streptococcal glomerulonephritis, it is caused by a preceeding Group A beta haemolytic streptococcus pharyngitis. This usually occurs around 2 weeks after infection. Anti-streptolysin O titre (ASOT) will be raised

28
Q

What is rapidly progressive glomerulonephritis?

A

Very agressive and can cause end-stage renal failure over a period of days

Three subtypes that are distinguished on immunofluoresence of IgG/C3:
Immune complex disease - granular staining
Pauci-immune disease - absent/scant staining
Anti-glomerular basement membrane - linear staining

29
Q

What is membranoproliferative glomerulonephritis?

A

Mesangial cell proliferation with thickening of the capillaries

Two types:
* Type 1 - classical and alternative complement pathway activation
* Type 2 - only alternative pathway activation

30
Q

What test is used to detect specific antibodies in serum for HIV?

A

Western blot

31
Q

What test is used to diagnose sarcoidosis?

A

Kveim test - sample of spleen from a patient with known sarcoid is injected intradermally into a suspected patient. A positive test is if there is a non-caseating granuloma formation at the site 4-6 weeks after the initail injection.

This is not used in the UK.

32
Q

What test is used to diagnose Henoch-Schönlein purpura?

A

Immunofluorescence test where anti-IgA antibodies will demonstrate IgA deposits within the capillary walls of a biological specimen from a patient

33
Q

What complement result would you expect in a person with rheumatoid arthritis?

A

High CH50 - measures the total complement activity of the complements in the classical and final pathways.

As RA is an inflammatory conidtion with complements being acute phase proteins, you would expect CH50 to be raised

34
Q

What is AP50?

A

It is a laboratory investigation for abnormalities of the alternative pathways which involes factors C3, B, D and P.

If AP50 is reduced and CH50 is normal, it suggests a deficiency in one or more alternative pathway factors, predisposing the individual to encapsulated bacteria infections

35
Q

What pattern does mebranoproliferative glomerulonephritis present with?

A

Reduced C3 but normal C4

*Think C3 nephritic factor

36
Q

How are mast cells activated?

A

Direct injury (toxins or drugs)
Cross-linking of IgE receptors
Activated complement proteins

*Once activated they release histamine and heparin

37
Q

What HLA is associated with coeliac disease?

A

HLA DQ2 - binds with great affinity to alpha-gliadin

*HLA DQ8 is also a risk factor but to a lesser extent

38
Q

What is molecular mimicry?

A

Pathogens produces antigens that are molecularly very similar to self antigens - the immune system generates T and B cells which are both anti-pathogen and anti-self (immunological cross-reactivity).

An example is in post-streptoccoal rheumatic fever where antibodies to M-proteins on GAS cross-react with cardiac myosin.

39
Q

What condition is associated with immune dysregulation?

A

Immunodysregulation polyendocrinopathy enteropathy X-linked syndrome (IPEX) due to abnormal Foxp3

40
Q

What forms the membrane attack complex?

A

C5, C6, C7 and C8 (part of the terminal compliment pathway). They form the MAC for bacteriolysis. Deficiency in the termianl compliment pathwya factors leads to encapsulated bacterial infections

*While C9 also forms part of the MAC, patients deficient in C9 can still clear encapsulated bacterial infections albeit at a slower rate

41
Q

What is oral allergy syndrome?

A

It occurs secondary to cross-reactivity of antigens inhaled in the mouth (alal pollen-food allergy)

For example a patient might be sensitised to birch pollen however birch pollen IgE might cross-react with a fruit that is similar. This can cause a release of histamine from mast cells creating local inflammation (but only contained within the wouth - swelling, tiching and tingling of the tongue, lips and uvula)

42
Q

What is the best test to identify allergies in general?

A

Skin prick test

43
Q

What is the best test for food allergies?

A

Double-blind challenge

44
Q

What is the radioallergosorbent test?

A

To test for a variety of potential allergens - patient serum is added to a range of insoluble allergens

45
Q

Which antibodies are targeted in pemphigus vulgaris?

A

Demoglein 1 and demoglein 3 - epidermal cadherins of the epidermis

46
Q

When do the following types of graft rejections occur?

Hyperacute rejection
Acute cellular rejection
Chronic rejection
Acute vascular rejection
Graft-versus-host disease

A

Hyperacute rejection - within minutes to hours (e.g. ABO incompatibility)

Acute cellular rejection - occurs 1 week after transplant (Type IV hypersensitivity)

Chronic rejection - involves both immune and non-immune reactions: smooth muscle growth causes blockage of graft vessel lumen with ischaemia and fibrosis (RF includes HLA-mismatches and multiple acute rejections)

Acute vascular rejection - usually post-xenograft transplant (similar to hyperacute but occurs 4-6 days post-transplant)

Graft-versus-host disease - post-allogenic stem cell transplant where immune cells recongise donated stem cells as foreign

47
Q

How does HIV first bind do CD4+ T cells?

A

The gp120 envelope glycoprotein on HIV binds to the CXCR4 receptor on the CD4+ T cell

48
Q

What is pIasmapheresis and in which conditions is it useful?

A

A method to rapdily remove circulating auto antibodies. Plasma is treated to remove the antibodies and then reinfused.

This can be doen in myasdthenia gravis and Goodpasture’s syndrome

49
Q

Where would you find the following immunofluorescence stain patterns?

Homogenous
Nucleolar
Speckled
Peripheral
Kinetoplast

A

Homogenous - anti-histone in SLE
Nucleolar - anti-RNA polymerase in systemic sclerosis
Speckled - anti-nuclear antibodies (ANA) e.g. dermatomyositis or polymyositis
Peripheral - anti-dsDNA in SLE

50
Q

Which factors play a role in fbrosis in systemic sclerosis?

A

TGF-beta and platelet derived growth factor (PDGF)

51
Q

Which autoantibdoues to tyrosine phosphate are detected in T1DM?

A

Anti-IA-2 antibody and anti-phogrin antibody

*Anti-GAD is highly present in T1DM but its target is not beta-cell specific. It affects the conversion of glutamate to GABA which is involved in insuline release from beta-cells.

52
Q

Which autantibody is responsible for Grave’s disease?

A

Stimulating anti-TSH receptor is the most important one. Thyroid growth stimulating antibody can also be seen.

*Non-stimulating anti-TSH receptor is a cause of primary hypothyroidism

53
Q

What autoantibodies are present in Hashimoto’s thyroiditis?

A

Anti-thyroid peroxidase (thyroid peroxidase is an enzyme required in the iodination of thyroglobulin)
and
Anti-thyroglobulin

54
Q

What autoantibodies are associated in autoimmune hepatitis?

A

Type 1: anti-nuclear antibodies and anti-smooth muscle antibodies

Type 2 (more common in paediatric population): Anti-liver kidney microsomal antibodies

55
Q

What is stiff man syndrome associated with?

A

Highly associated with GAD antibodies but only a small minority of T1DM patients suffer from stiff man syndrome

56
Q

What autoantibody is Guillian Barrè syndrome associated with?

A

Ganglioside LM1 (part of nerve myelin). There is cross-reactivity between pathogen antibodies and ganglioside LM1

57
Q

What is sympathetic opthalmia?

A

Granulomatous CD4+ T cell-mediated disease that attack the eye. This usually occurs post-trauma with increased photoreceptor antigen presentation to immune cells and cytokine release

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