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Path - Immuno > primary immunodeficiencies 2 > Flashcards

primary immunodeficiencies 2 Flashcards

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1
Q

Recurrent infections with high neutrophil count on FBC but no abscess formation is consistent with?

A

Leukocyte adhesion deficiency

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2
Q

Soluble components: Cytokines and chemokines are part of which immune system

A

adaptive

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3
Q

whichare the lymphoid organs? role?

A

bone marrow
- b cell maturation site

thymus
- t cell maturation site

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4
Q

what are the types of SCID? Aetiology?

A
  1. X-linked SCID:
    45% of all severe combined immunodeficiency.
    Mutation of common gamma chain (gc) on chromosome Xq13.1.
  2. ADA deficiency:
    16.5% of all severe combined immunodeficiency
    Adenosine Deaminase Deficiency
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5
Q

what are the types of SCID? Aetiology?

A
  1. X-linked SCID:
    45% of all severe combined immunodeficiency.
    Mutation of common gamma chain on chromosome Xq13.1.
  2. ADA deficiency:
    16.5% of all severe combined immunodeficiency
    Adenosine Deaminase Deficiency
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6
Q

what is the phenotype of ADA deficiency?

A

Very low or absent T cell numbers
Very low or absent B cell numbers
Very low or absent NK cell numbers

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7
Q

What protects the SCID neonate in the first 3 months of life?

A

Source of circulating maternal IgG in the neonate

after 3 months their igG production should increase but in scid it doesn’t

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8
Q

what is the clinical phenotype of severe combined immunodeficiency?

A

Unwell by 3 months of age
Infections of all types
Failure to thrive
Persistent diarrhoea

Unusual skin disease:
-Colonisation of infant’s empty bone marrow by maternal lymphocytes
-Graft versus host disease
Family history of early infant death

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9
Q

what is the state of t cells beefore and after thymus?

A

before - pre T cells

after - mature T cells

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10
Q

which receptors do T cells present?

A

CD3
+
CD4 OR CD8

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11
Q

which molecules do T cells bind to be activated?

A

CD8+ cytotoxic T cells recognise peptide presented by HLA class I molecules

CD4+ T cells recognise peptide presented by HLA class II molecules

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12
Q

what is the theory of Selection and Central Tolerance for T cells?

A

T cells with Low affinity for HLA are NOT selected in the thymus. prevent iniadequate reactivity

Those with High affiniity are NEGATIVELY selected - prevent autoreactvity

Only those with interrmediate affiinity get though - 10% of initial population

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13
Q

what iis thee theory of Selection and Central Tolerance for T cells?

A

T cells with Low and High affinity for HLA are NOT selected in the thymus.

only those with interrmediate affiinity get though - 10% of initial population

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14
Q

what is the role of CD8+ cytotoxic T cells ?

A

Kill cells directly
Perforin (pore forming) and granzymes
Expression of Fas ligand

Secrete cytokines eg IFNg TNFa

Particularly important in defence against viral infections and tumours

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15
Q

what is the role of CD4+ T helper cells ?

A

Immunoregulatory functions

via cell:cell interactions and expression of cytokines

Provide help for development of full B cell response
Provide help for development of some CD8+ T cell responses

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16
Q

what is the role of CD4+ T follicular helper cells ?

A

Immunoregulatory functions

via cell:cell interactions and expression of cytokines

Provide help for development of full B cell response
Provide help for development of some CD8+ T cell responses

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17
Q

which CD4 T Cell helps in neutrophil recruitment?

A

Th17

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18
Q

which CD4 T Cell helps in neutrophil recruitment?

A

Th17

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19
Q

what is the role of Th1?

A

helps in macrophage and CD8 T cell recruitment

secret IL2
TNFa
IFN-y

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20
Q

what is the role of Treg? what does it express?

A

regulates t cell responses

CD25
Foxp3 - a transcription factor

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21
Q

t helper cells express what?

A

CD4

Th2

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22
Q

List some examples of defects in T cell maturation?

A
  1. 22q11.2 deletion syndromeeg DiGeorge syndrome
  2. MHC Class II deficiency (absent) = cd4 not selected examples:Bare lymphocyte syndrome – type 2:
    • Regulatory factor X
    • Class II transactivator
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23
Q

what is the aetiology of DiGeorge syndrome?

A

Deletion at 22q11.2
Usually sporadic not inherited

Developmental defect of pharyngeal pouch

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24
Q

what is the immune phenotyope of di george?

A

Normal numbers B cells
Reduced numbers T cells
Homeostatic proliferation of T cells
Immune function usually only mildly impaired and improves with age - due to the homeostatic proliferation

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25
the following features are pathognomic of what: ``` High forehead Hypocalcaemia Oesophageal atresia Underdeveloped thymus Complex congenital heart disease ```
DiGeorge syndrome
26
how does Bare lymphocyte syndrome – type 2 present?
Unwell by 3 months of age Infections of all types Failure to thrive Family history of early infant death ivx: Profound deficiency of CD4+ cells as arent selected Low IgG or IgA antibody due to lack of CD4+ T cell helper cell
27
list some Disorders of T cell effector function?
Cytokine production – IFN Cytokine receptors – IL12 receptor Cytotoxicity T-B cell communication
28
list some Disorders of T cell effector function?
Cytokine production – IFN Cytokine receptors – IL12 receptor Cytotoxicity T-B cell communication
29
how can we InvestigateT cell deficiencies?
Total white cell count and differential Remember that lymphocyte counts are normally much higher in children than in adults Lymphocyte subsets Quantify CD8 T cells, CD4 T cells as well as B cells and NK cells Immunoglobulins If CD4 T cell deficient Functional tests of T cell activation and proliferation Useful if signalling or activation defects are suspected HIV test
30
what would ivx results show in DiGeorge?
Low CD4/8 t cells Low igG normal B cell and Igm
31
what would ivx results show in DiGeorge?
Low CD4/8 t cells Low igG normal B cell and Igm
32
what would ivx results show in SCID
everything low B cell and igM may be normal occasionally
33
what is the Management of Immunodeficiency involving T cells?
Aggressive prophylaxis/treatment of infection Haematopoieitic stem cell transplantation To replace abnormal populations in SCID To replace abnormal cells - class II deficient APCs in BLS Enzyme replacement therapy PEG-ADA for ADA SCID Gene therapy Stem cells treated ex-vivo with viral vectors containing missing components. Transduced cells have survival advantage in vivo. Thymic transplantation To promote T cell differentiation in Di George syndrome
34
what is the Management of Immunodeficiency involving T cells?
Aggressive prophylaxis/treatment of infection Haematopoieitic stem cell transplantation To replace abnormal populations in SCID To replace abnormal cells - class II deficient APCs in BLS Enzyme replacement therapy PEG-ADA for ADA SCID Gene therapy Stem cells treated ex-vivo with viral vectors containing missing components. Transduced cells have survival advantage in vivo. Thymic transplantation To promote T cell differentiation in Di George syndrome
35
what is the condition: Severe recurrent infections from 3 months,CD4 and CD8 T cells absent, B cell present, Igs low. Normal facial features and cardiac echocardiogram
X-linked SCID
36
what is the condition: Young adult with chronic infection with Mycobacterium marinum
IFN gamma receptor deficiency
37
what is the condition: 6 month baby with two recent serious bacterial infections. T cells present – but only CD8+ population. B cells present. IgM present but IgG low
Bare lymphocyte syndrome type II
38
what is the B cell response when an antigen contacts the body ?
2 pathways: 1. Early IgM response – T cell independent - IgM memory cell and Ab secreting plasma cell 2. ii) Germinal centre reaction in lymph node –CD4+ T cell dependent; A. Dendritic cells prime CD4+ T cells B. CD4+ T cell help for B cell differentiation. Requires CD40L:CD40 C. B cell proliferation. Somatic hypermutation.Isotype switching to IgG, A , E The somatic hypermutation leads to receptor editing which allows memory cells and plasma cells with higher affinity for antigens to be selected for.
39
which chain on an anitbody determines the antibody class (eg IgM, IgE etc)?
Heavy chain
40
which chain on an anitbody determines the antibody class (eg IgM, IgE etc)?
Heavy chain
41
what is the structure of an IgM?
pentamer
42
Effector function is determined by the ________ ?
constant region of the heavy chain (Fc)
43
Effector function is determined by the ________ ?
constant region of the heavy chain (Fc)
44
Antibody Interacts with other components* of immune response to remove pathogens. this is mediated by ____? *Complement Phagocytes Natural killer cells
Fc mediated
45
what is the aetiology and presentation of Bruton’s X linked agammaglobulinaemia?
Abnormal/ Muation in the B cell tyrosine kinase (BTK) gene on the X chromosome = Pre B cells cannot develop to mature B cells Absence of mature B cells - so cant make antibodies No circulating Ig after ~ 3 months
46
what is the presentation of Bruton’s X linked agammaglobulinaemia?
Boys present in first few years of life Recurrent bacterial infections Otitis media, sinusitis, pneumonia, osteomyelitis, septic arthritis, gastroenteritis Viral, fungal, parasitic infections Enterovirus, Pneumocystis, Failure to thrive
47
what is Hyper IgM syndrome? Aetiology?
B cell maturation defect due to Failure of T cell costimulation X-linked recessive !! Mutation in CD40 ligand (CD40L) gene - which is usually expressed by T cells not B The Germinal centre reaction that allows for affinity maturation and isotype switching does NOT occur only have IgM antibodies
48
which of the following is correct: A. Hyper IgM syndrome is caused by mutation in CD40 ligand gene, resulting in failure of activation of B cells (expressing CD40 ligand) by T cells (expressing CD40) (Failure of T cell costimulation). B. Hyper IgM syndrome is caused by mutation in CD40 ligand gene, resulting in failure of activation of B cells (expressing CD40) by activated T cells (expressing CD40 ligand. Failure of T cell costimulation.
B
49
what is isotype switching?
usually switching from IgM to A,E etc
50
what results would be seen in ivx of Hyper IgM syndrome?
Normal number circulating B cells Normal number of T cells but activated cells do not express CD40 ligand No germinal centre development within lymph nodes and spleen Failure of isotype switching Elevated serum IgM Undetectable IgA, IgE, IgG
51
what is the clinical phenotype of hyper IgM syndrome?
Only difference from others is that: There's a subtle abnormality in T cell function predisposes to Pneumocystis jiroveci infection, autoimmune disease and malignancy
52
what is the clinical phenotype of hyper IgM syndrome?
Only difference from others is that: There's a subtle abnormality in T cell function predisposes to Pneumocystis jiroveci infection, autoimmune disease and malignancy
53
what results would be seen in Common variable immune deficiency CVID?
Marked reduction in IgG, with low IgA or IgM , low IgE Poor/absent response to immunisation Absence of other defined immunodeficiency Recurrent bacterial infections
54
what is the clinical phenotype of CVID?
Clinical features – ADULTS! and children Recurrent bacterial infections Pulmonary disease Gastrointestinal disease Malignancy - NHL Autoimmune disease: eg Autoimmune haemolytic anaemia or thrombocytopenia
55
what is the aetiology and epidemiology of Selective IgA deficiency?
Prevalence = 1:600 2/3rd individuals asymptomatic 1/3rd have recurrent RESPIRATORY tract infections Genetic component, but cause as yet unknown
56
how can Investigation of B cell deficiencies be done?
Total white cell count and differential Lymphocyte subsets - quantfy them Serum immunoglobulins and protein electrophoresis Functional tests of B cell function - eg measure specific antibody responses to known pathogens
57
Production of IgG is surrogate marker for _____? why?
CD4 T cell helper function because T helper cell costimulation via CD40 ligand iis required to activate B cell maturation which allows foramtion of plasma cells.
58
on protein elctrophoresis, what would you see on Common variable immune deficiency CVID?
undetectable gamma/y band because in this condition, there are no antibodies
59
What is the management of Immunodeficiency involving B cells?
Aggressive prophylaxis / treatment of infection Immunoglobulin replacement if required Derived from pooled plasma from thousands of donors Contains IgG antibodies to a wide variety of common organisms Aim of maintaining trough IgG levels within the normal range Treatment is life-long Immunisation For selective IgA deficiency
60
What is the management of Immunodeficiency involving B cells? eg for Bruton etc
Aggressive prophylaxis / treatment of infection Immunoglobulin replacement if required -Derived from pooled plasma from thousands of donors Contains IgG antibodies to a wide variety of common organisms Aim of maintaining trough IgG levels within the normal range Treatment is life-long Immunisation For selective IgA deficiency
61
Adult with bronchiectasis, recurrent sinusitis and development of atypical SLE
Common variable immunodeficiency
62
Recurrent bacterial infections in a child, episode of pneumocystis pneumonia, high IgM, absent IgA and IgG
X linked hyper IgM syndrome due to CD40ligand mutation
63
1 year old boy. Recurrent bacterial infections. CD4 and CD8 T cells present. NO B cells, IgG, IgA, IgM absent
Bruton’s X linked hypogammaglobulinaemia
64
Recurrent respiratory tract infections, absent IgA, normal IgM and IgG
IgA deficiency
65
which antiibody is absent in Bruton’s X linked hypogammaglobulinaemia?
all antibodies because gammaglobulins are antibodies - this word does NOT refer just to IgG
66
At 3 months, a baby boy is discovered to have a BTK gene mutation. What should his vaccination schedule look like?
Cant get any live vaccines eg MMR prophylaxis for infection

Path - Immuno (11 decks)

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