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Disease Mechanisms > Immunology - Immune Deficiences > Flashcards

Immunology - Immune Deficiences Flashcards

1
Q

What are the major hallmarks of immune deficiency?

A

Serious Infections

Persistent Infections

Unusual Infections

Recurrent Infections

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2
Q

What is a feature of Serious Infection?

A

Unresponsive to antibiotics

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3
Q

What are features of persistent infections?

A

Early structural damage

Chronic infection

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4
Q

What are features of unusual infections?

A

Unusual organisms

Unusual sites

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5
Q

How are recurrent infections defined?

A

Two major

or

One major and recurrent minor infections in one year

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6
Q

What other features may be suggestive of primary immune deficiency?

A

Weight loss/failure to thrive

Severe skin rash

Chronic diarrhoea

Mouth ulceration

Unusual autoimmune disease

Family history

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7
Q

How are immunodeficiencies classified?

A

Primary

rare 1:10,000 live births

> 100 now described

Secondary

common

often subtle

often involves more than one component of immune system

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8
Q

What are clinical features of phagocyte deficiency?

A

Recurrent infections at both common and unusual sites

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9
Q

Which organisms are associated with phagocyte deficiency?

A

Common bacteria, e.g. Staph Aureus

Unusual bacteria, e.g. Burkholderia cepacia

Mycobacteria (both TB and atypical)

Fungi - candida, aspergillus

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10
Q

Why may treatment for leukaemia cause serious bacterial infection?

A

Neutrophils numbers fall to very low levels - neutropaenia

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11
Q

Where can things go wrong in the life cycle of a neutrophil?

A

Mobilisation from bone marrow or within tissues

Adhesion and migration into tissue

Phagocytosis

Activation of other immune components

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12
Q

What are examples of failure to produce neutrophils?

A

Failure of stem cells to differentiate along myeloid lineage:

Recticular dysgenesis - primary defect

After stem cell transplantation - secondary defect

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13
Q

Give examples of the failure of neutrophil maturation.

A

Kostmann syndrome - severe congenital neutropaenia, autosomal recessive

Cyclic neutropaenia - episodic neutropaenia every 4-6 weeks

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14
Q

What is the clinical presentation of Kostmann syndrome?

A

Infections usually within 2 weeks after birth

Recurrent bacterial infection, may be systemic or localized

Fever

Irritability

Oral ulceration

Failure to thrive

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15
Q

What is the management of Kostmann syndrome?

A

Prophylactic antibiotics

Prophylactic antifungals

Stem cell transplantation

Granulocyte colony stimulating factor (G-CSF) to assist maturation of neutrophils

WIthout definitive treatment 70% mortality in first year.

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16
Q

What is the clinical picture of Leukocyte adhesion deficiency?

A

Marked leukocytosis

Localised bacterial infections that are difficult to detect

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17
Q

What is leukocyte adhesion deficiency?

A

Rare primary immunodeficiency caused by genetic defect in leucocyte integrins (CD18) resulting in failure of neutrophil adhesion and migration

18
Q

What is chronic granulomatous disease?

A

Deficiency of intracellular killing mechanisms of phagocytes:

inability to generate oxygen free radicals

impaired kiling of intracellular microorganisms

Commonest form is X-linked (NADPH oxidase)

19
Q

Why are granulomas formed in Chronic Granulomatous Disease?

A

Inability to clear organisms leads to persistant accumulation of neutrophils, activated macrophages and lymphocytes resulting in granuloma formation.

20
Q

What are the features of chronic granulomatous disease?

A

Recurrent deep bacterial infections

Staph, Aspergillus, pseudomonas, mycobacteria

Recurrent fungal infections

Failure to thrive

Lymphadenopathy

Hepatosplenomegaly

Granuloma formation

21
Q

How is chronic granulomatous disease investigated?

A

NBT (nitroblue tetrazolium) test

Dye changes colour if neutrophils produce H2O2.

22
Q

What is the management for chronic granulomatous disease?

A

prophylactic antibiotics

prophylactic antifungals

Stem cell transplantation

(gene therapy)

23
Q

Which organisms tend to hide from immune system within cells?

A

Salmonella

Chlamydia

Ricksettia

Mycobacteria (within macrophages)

24
Q

Defects in which axis are associated with susceptibility to intracellular bacteria?

A

IL12-gIFN axis

25
Q

What is involved in the IL12-gIFN axis?

A

IL12 secreted by macrophage induces T cells to secrete gIFN

gIFN stimulates production of TNF

TNF activates NADPH oxidase stimulating oxidative pathways killing intracellular bacteria

26
Q

What is an important side effect of anti-TNF drugs?

A

Reactivation of latent TB

27
Q

What is severe combined immunodeficiency?

A

Failure of production of lymphocytes from stem cells

28
Q

What is the clinical presentation of severe combined immunodeficiency?

A

Unwell by 3 months age

Persistant diarrhoea

Failure to thrive

Infections of all types including vaccine associated diseases

Unusual skin disease - Graft vs host

Family history of early infant death

29
Q

Why does severe combined immunodeficieny present around 3 months of age?

A

Because the neonate is protected by maternal IgG for the first 3 months of life.

30
Q

What is transient hypogammaglobulinaemia?

A

Slow maturation of immune system in normal babies presenting with infection at around 3-4 months

31
Q

What is the commonest form of Severe Combined Immunodeficiency?

A

X-Linked SCID

Mutation of component of IL2 receptor resulting in inability to respond to cytokines

Failure of T cell and NK cell development

Production of immature B cells

32
Q

What is the clinical phenotype of X-linked SCID?

A

Very low or absent T cells

Normal or increased B cells

Poorly developed lymphoid tissue and thymus

33
Q

What is the treatment for SCID?

A

Prophylactic Antibiotics

Prophylactic Antifungals

No Vaccines

Aggressive treatment of infection

Antibody replacement - IV Ig

Stem cell transplant (HLA identical sibling if possible)

34
Q

What is DiGeorge syndrome?

A

Deletion of chromosome 22q11

Developmental defect of 3rd/4th pharyngeal pouch

Low set, abnormally folded ears

High forehead, cleft palate, small mouth and jaw

Hypocalcaemia (secondard to hypoparathyroidism)

Oesophageal Atrasia

T cell lymphoma

Complex congenital heart disease

35
Q

What kind of infections is a child with DiGeorge syndrome susceptible to?

A

viral (CD8 T cells)

bacterial (CD4 T cells)

fungal infections

36
Q

What laboratory results would point to DiGeorge syndrome?

A

Absent/decreased T cells

Normal or increased B cells

Low IgG, IgA, IgE

Poor antibody response to specific pathogens

Normal NK cell numbers

37
Q

What is the management of DiGeorge syndrome?

A

Correct metabolic/cardiac anomalies

Prophylactic antibiotics

Aggressive treatment of infection

Immunoglobulin replacement

T cell function improves with age

38
Q

What are the clinical features of T cell deficiencies?

A

Recurrent viral, bacterial, fungal, intracellular pathogen infections

Opportunistic infections

Malignancies at young age

Autoimmune disease

39
Q

What is the presentation of antibody deficiences?

A

Recurrent bacterial infections, often common organisms - LRTI, URTI, GI

Viral infections are less common but may occur

Antibody mediated autoimmune disease:

Idiopathic thrombocytopaenia

Autoimmune haemolytic anaemia

40
Q

What is Bruton’s X-linked hypogammaglobulinaemia?

A

Failure to produce mature B cells, resulting in

no circulating B cells

no plasma cells

no circulating antibody after the first 6 months

41
Q

What is common variable immune deficiency?

A

Low IgG, IgA and IgE

Recurrent bacterial infections - severe end organ damage, bronchiectasis, persistent sinusitis, recurrent GI infection

Often associated with autoimmune disease

Granulomatous disease

42
Q

How are B cell deficiencies managed?

A

Aggressive treatment of infection

Immunoglobulin replacement, IV every 3-4 weeks

Stem cell transplantation in some situations

Disease Mechanisms (9 decks)

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