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FPP Block 1 > Overview of Primary Immune Deficiencies (PID) > Flashcards

Overview of Primary Immune Deficiencies (PID) Flashcards

1
Q

What are Primary Immune Deficiencies and how do they compare to secondary immune deficiencies?

A
  • PIDs are intrinsic defects in the immune system that are usually but not always inheritied
  • secondary immune deficiencis are due to extrinsic factors that suppress the immune response (drugs or HIV)
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2
Q

When should you suspect PID?

A
  • too many infections, or infections that won’t go away (>2 pneumonias or a lot of sinus infections)
  • Weird infections or locations of infections (lung/liver abscess, or Pneumocystis jerovecii)
  • Early onset immunity, weird patters of autoimmunity or immunodysregulation (eg IB in a baby)
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3
Q

WHat are some things that lead to secondar immunodeficiencies?

A
  • infections
  • malnutrition
  • malignancies
  • metabolic
  • loss of lymphocytes or antibodies
  • immunosuppresants
  • collagen vascular disease
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4
Q

What are the two things that tests of immune function measure?

A
  1. Number or quantitiy (are there enough PMNs)
  2. Function (do the PMNs work)
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5
Q

What cell surface protein(s) do all T cells have?

A

CD3- all T cells

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6
Q

What cell surface protein(s) do naive T cells have

A

CD3+CD45RA

**A for nAive**

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7
Q

What cell surface protein(s) do memory T cells have

A

CD3+CD45RO

**O for MemOry**

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8
Q

What cell surface protein(s) do helper T cells have

A

CD3+/CD4+

helper T cells

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9
Q

What cell surface protein(s) do Cytotoxic T cells have?

A

CD3+CD8+

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10
Q

What cell surface protein(s) do all B cells have

A

CD19 or CD20

All B cells

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11
Q

NK Cell markers

A

CD3-/CD56+

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12
Q

What are the clinical manifestations of neutrophil defects?

A
  • onset early in infacny/childhood
  • severe bacterial infections
  • abscesses
  • gingival/peridontal disease
  • Poor wound healing/lack of pus
  • common pathogens: catalase + organs
    • staphylococcus, aspergillus, nocardia, burkholderia (CGD or CF)
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13
Q

List 3 examples of diseases that are neutrophil defects

A
  • chronic granulomatous disease (CGD)
  • congenital/cyclic neutropenia
  • Leukocyte adhesion deficiency
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14
Q

What is the workup when neutrophil defects are suspected?

A
  1. Initaial
    1. NUMBER: CBC with differential- look at abosolute numbers of WBCs including the absolute neutrophil count (ANC)
    2. FUNCTION: Dihydroorhodamine test (DHR)
      1. ​sometimes Nitroblue tetrazolium (NBT)-older
  2. Secondary
    1. chemotaxis
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15
Q

WHat is the clinical manifestation of a complement defect?

A
  • any age
  • “classical” complement pathway defects are most common
  • Two types:
    • Early (C2, C4) Defects
      • autoimmune disease most common presentation (SLE, glomerulonephritis)
      • Sinopulmonary infections, sepsis, increased susceptibility to S. pneumoniae, H. influenzae
    • Late (C5-C9 defects)
      • increased suseptibility to Neisseria infections
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16
Q

describe early and late complement defects

A
  • Early (C2, C4) defects
    • autoimmune disease is the most common presentation
    • often see sinopulmonary infections, sepsis, increased susceptibiloty to S. pneumoniae, H. influenzae
  • Late (C5-C9) defects
    • increased susseptibility to Neisseria
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17
Q

What is the workup if you suspect a complement defect

A
  • Initial
    • CH50 (functional assay for all of the classical complemts)
      • if there is a complement deficiency CH50=0 usually, but if it is just a problem with complement consumption (ie Lupus) then CH50 is low but not 0.
  • Secondary
    • do individual component testing is CH50 is low. If if is not zero suspect complement consumption problem (ie Lupus)
      *
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18
Q

What is the clinical manifestation of a B-cell/ Antibody defect? and examples

A
  • Antibody deficiencies are the most common PID (50%)
  • Agammaglobulinemias usually presnet in first year or two of life; CVID at any age
  • you would see: recurrent sinopulmonary bacterial infections, infections with encapsulated organisms like (H. flu, S. pneumo and mycoplasma sp.) chronic GI infections, malabsoprtion and FTT

Ex: XLA, CVID

19
Q

What is the work up for a B-cell/Antibody Defect?

A
  • Quantitative immunoglobins (IgG/A/M/E) -note can be influenced by secondary immunosuppression
  • vaccine titiers-if low reimmunize and measure titier 4 wks later
  • consider
    • lymphocyte substs
    • CH50
    • sweat chloride
20
Q

What is teh clinical manifestation of a T cell or combined T cell/B cell Defect?

A
  • Recurrent severe infections: viruses Idisseminated CMV, EBV, Varicella), Funal (candidiasis) bacteria, opportunistic pathogens (P. jiroveci, mycobacteria)
  • poor growth/FTT/chronic diarrhea
  • SCID-onset first year of life usually after maternal antibodies wane
  • combined B/T: SCID
21
Q

WHat is the workup if you suspect T-cell/combined defects?

A
  • CBC w differential: a low absolute lymphocyte count (ALC) can be a helpful clue
  • Lymphocyte susbset enumeration (flow cytometry)
    • Numbers ot T/B/NK cells, memory and naive T cells
    • Quantitative IgGs (IgM, IgG, IgA)
    • T cell proliferation
22
Q

Example os combined B cell and T cell and the screening?

A

SCID

  • Screen:
    • Lymphocyte susbsets (T and B cells/NK cells) by flow cytometry; T proliferative response to mitogens (PHA)
23
Q

Example of a T cell immunodeficiency

A

DiGeorge Syndrome

Test:

Lymphocyte susbsets: FISH for 22.q11.2 deletion, RT-PCR for TBX1 gene

DNA chromocome microarray (preffered)

24
Q

Examples of antibody immunodeficiency

A

XLA, CVID

TestL IgG, IgA and IgM-not IgG subclasses

25
Q

Example of PMN immunodeficiency

A

CGD

Dihydroorhodamine (DHR) test

26
Q

Example of complement deficiency

A

C2 (early), C5-9 (late)

TestL CH50

27
Q

describe the molecular basis of X-Linked SCID and what does this mean?

A
  • mutation in the common gamma chain of the IL-2 receptor. This s a common component for other Il receptors too!
  • Therefore they lack T cells and NK cells, and B cells are present but not functional
  • naive T cells are reduced in all forms of SCID
28
Q

clinical manifestation of SCID

A

onset in infancy, neumonia ( P. jiroveci) otitis media, trush, intractable diarrhes, FTT

bone marrow transplant can help!

29
Q

Diagnostic test for SCID. screening and confirmatory

A

screening test: CBC, lymphopenia

confirmatory: lymphocyte enumeration ( T cells, naive/memory, B cells, NK cells)

30
Q

Describe the newborn screening test for SCID

A
  • While making a T cell receptor T cells uncergo rearrangement resulting in small fragments of nonreplicating DNA being released called TRECs
  • these TRECs when measure by RT-PCR are a marker for numbers of normal naive T cells

If TRECs are low suspect SCID!

31
Q

What causes DiGeorge syndrome?

A
  • Microdeletion in chromosome 22q11.2 leading to defect in 1st to 6th pouches: deletion TBX1 gene is a common cause
  • Common!
32
Q

Clinical manifestations of DIGeorge Syndorme

A
  • CATCH 22
    • Cardiac Defects
    • Abnormal Facies- low set ears
    • THymic hypoplasia
    • CLeft palate
    • HYpocalcemia
    • 22nd chromosome
  • Chronic infection/autoimmunity
  • T cell abnormalities: low T cell counts
  • Antibody deficiency
33
Q

How do you diagnoseDiGeorge syndrome?

A

DNA microarray (copy number variation), FISH

RT-QPCR for hploinsufficiency TBX1 (CHF)

34
Q

Clinical manifestation of XLA

A
  • recurrent otitis, sinusitis, pneumonia
  • Early dx/Rx to prevent bronchiectasis
  • encapsulated bacteria (S pneumo and H influenzae) and mycoplasma
  • sever enteroviral infections
  • onset early infancy or childhood in most

mutations in Btk result in failure to differntiate B cells

35
Q

Screening for XLA

A

IgG, IgA, IgM-best screening test for ALL Ab deficiencies

36
Q

Clinical manifestations for Common Variable Immunodeficiency (CVID)

A
  • most common PID
  • onset at any age
  • infections: RTI most common
  • Pulmonary disease: bronchiectasis and interstitial lung disease this typically the cause of death
37
Q

How do you diagnose CVID

A
  • decrease in IgG and low IgA and/or IgM
  • absent isohemagglutinins and poor response to vaccines
  • exclude primary Ab deficiency (XLA) or secondar Ab deficiency
38
Q

manifestation of IgA Deficiency

A
  • most common AB deficiency
  • low IgA but ormal IgG and IgM
  • no phenotype sometime GI infectiions
39
Q

Specific Antibody deficiency manifestation

A
  • recurrent sinopulmonary infections
  • normal IgG, IgA and IgM and normal T cell fucntin
  • Abnormal specific antibody reponse to immunization especiall Polysaccharides-have all the right toll djust can’t really elicit response. will grow out of it
40
Q

What are the lab tests for diagnosing Antibody deficiencies

A
  • serum IgG, IgA, IgM
    *
41
Q

Compare lab results of XLA to CVID

A

XLA: decrease in all isotypes

CVIDL decrease in 2 of 3 isotypes INCLUDING IgG

Both XLA and CVID have poor specific Ab response to vaccines

**Do PCR to diagnose Ab deficiency

42
Q

Manifestation of Chronic Granulomatous Disease (CGD)

A
  • hepatic absess without obvious source in young child
  • infection w catalase + bacteria
43
Q

DIagnosis of CGD

A

DHR

Note some people can be carriers bc its often X-linked

44
Q

WHat is the best screening for all classical compement deficiencies?

A

CH50

FPP Block 1 (18 decks)

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