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YR5 Immunology > Innate Immunity and deficiencies > Flashcards

Innate Immunity and deficiencies Flashcards

1
Q

Describe phagocytosis

A
  1. Pathogen taken into phagosome
  2. Phagosome fuses with Lysosome. Oxidative (NADPH complex)/ non oxidative killing (Lysozyme + Lactoferrin).
  3. Depleted neutrophil glycogen- cell death + pus formation
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2
Q

Which receptors are expressed by natural killer cells?

A

Inhibitory receptors for self HLA
Activating receptors for Heparin sulphate proteogylcans

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3
Q

Other than bacteria, what do NK cells kill

A

Altered self- Malignant/ virus infected

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4
Q

Which proteins are found in the classical complement pathway?

A

C1
C2
C4

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5
Q

Which proteins are found in the mannose binding lectin complement pathway?

A

C4
C2

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6
Q

What activates the alternative complement pathway?

A

Bacterial cell wall component e.g. lipopolysaccharide

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7
Q

Which complement activation pathway is dependent on the acquired immune response?

A

Classical

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8
Q

On which complement protein do all pathways converge? What is the consequence of this?

A

C3
If defect/ deficiency all pathways affected

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9
Q

What does activation of C3 result in?

A

Final common pathway C5-9
formation of Membrane attack complex

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10
Q

What is the function of the membrane attack complex?

A

Opsonises pathogen
Activates immune cells
Activates more complement

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11
Q

What is the consequence of defects or deficiency in phagocytosis?

A

Recurrent deep bacterial infections: S. aureus
+ Enteric bacteria
Recurrent fungal infections: Candida albicans + Aspergillus spp.

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12
Q

Give 3 causes of failure of production of neutrophils

A

Reticular dysgenesis
Kostmann syndrome
Cyclic neutropenia

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13
Q

4 features of Reticular dysgenesis

A

Pancytopenia
No differentiation of stem cells
No granulocytes, no myeloid/ lymphoid cells
Most severe SCID

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14
Q

3 features of Kostmann syndrome

A

Severe congenital neutropenia
AR mutation in HAX1
Can’t produce neutrophils

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15
Q

3 features of Cyclic neutropenia

A

Episodic neutropenia every 4-6w
AD mutation in neutrophil elastase
Neutrophil count fluctuates ~monthly

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16
Q

What are the 4 failures causing defects/ deficiency of phagocytes?

A

Failure of production
Failure of trafficking
Failure of killing
Failure of signalling

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17
Q

What causes failure of trafficking to site of infection?

A

Leukocyte adhesion deficiency:
CD18 deficiency

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18
Q

Describe the pathophysiology of leukocyte adhesion deficiency

A

CD18 should form dimer with CD11 that binds ICAM-1 on endothelial cells to allow transmigration
Absence means neutrophils can’t leave bloodstream

19
Q

Give 3 characteristics of leukocyte adhesion deficiency

A

Very high neutrophil count
Absence of pus
Delayed umbilical cord sloughing

20
Q

What causes neutrophil failure of killing?

A

Chronic granulomatous disease

21
Q

Why do granulomas form in chronic granulomatous disease?

A

Neutrophils die quicker as use glycogen + lysozyme stores faster
Phagocytes fuse forming granuloma

22
Q

What causes chronic granulomatous disease?

A

NADPH oxidase deficiency
Thus no respiratory burst
Impaired killing of intracellular pathogens

23
Q

What causes excessive inflammation in chronic granulomatous disease?

A

Persistent neutrophil/ macrophage accumulation
Failure to degrade antigens

24
Q

Give 2 clinical signs of chronic granulomatous disease

A

Hepatosplenomegaly
Lymphadenopathy

25
Q

Which bacteria are patients with chronic granulomatous disease particularly susceptible to?

A

Catalase +ve PLACESS
Pseudomonas
Listeria
Aspergillus
Candida
E.coli
Staph aureus
Serratia

26
Q

Which tests can be used to diagnose chronic granulomatous disease?

A

Nitroblue tetrazolium (NBT): yellow to blue if oxidative killing. CGD -ve.
Dihydrorhodamine (DHR) flow cytometry: fluorescent if oxidative killing. CGD -ve.

27
Q

What causes a failure of signalling as a defect of phagocytosis?

A

IL12-IFN gamma pathway defect
Defect in cytokines or receptors

28
Q

What is the pathophysiology of IL12-IFN gamma pathway defect?

A

Defect in signalling between macrophages + T cells
Can’t activate T cells
Granulomas can’t be formed

29
Q

What are patients with IL12-IFN gamma pathway defect susceptible to?

A

Mycobacteria (TB + Atypical)
BCG
Salmonella

30
Q

What is classical NK deficiency?

A

Absent NK cells, not differentiating from stem cells
GATA4 or MCM4 mutations

31
Q

What is functional NK deficiency?

A

Abnormal function- too little/ too much (AI)

32
Q

What are those with NK cell deficiencies especially vulnerable to?

A

Herpes virus: HSV, VZV, EBV, CMV
Papilomavirus: HPV

33
Q

Which infections are those with complement deficiency particularly susceptible to?

A

Neisseria meningitides
Haemophilus influenzae
Streptococcus pneumonia

34
Q

What can cause complement deficiency?

A

Primary: body not making
Secondary: Liver failure, AI disease using up complement e.g. SLE

35
Q

What results from deficiency early in the classical complement pathway?

A

Not clearing apoptotic/ necrotic cells- increases self-antigens esp. nuclear, promotes AI
Not clearing immune complexes- deposition in skin, joints, kidneys + inflammation

36
Q

Which deficiency in the classical complement pathway is most common? What disease is this associated with?

A

C2
SLE

37
Q

What can cause a secondary deficiency in the classical complement pathway?

A

Active lupus
Due to persistent production of complexes + consequent depletion of complement
Low C3 + C4

38
Q

What can cause secondary C3 deficiency?

A

Nephritic factors; autoantibodies against C3 convertase
Cause constant activation + thus depletion of C3

39
Q

Which diseases may secondary C3 deficiency be seen in?

A

Glomerulonephritis: blood in urine
Lipodystrophy: abnormal fat distribution e.g. Lipomas

40
Q

Describe management of phagocyte deficiencies

A

Infection prophylaxis
Abx: Septrin PO/IV
Anti-fungals: Itraconazole

Definitive therapy:
HSCT: ‘Replaces’ defective population.

41
Q

What treatment is given in chronic granulomatous disease?

A

Interferon gamma therapy

42
Q

What investigations are used to diagnose complement deficiencies?

A

CH50
AP50

43
Q

Describe the management of complement deficiencies

A

Vaccination
Prophylactic abx
Screen family

YR5 Immunology (14 decks)

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