Immuno 4: Primary Immune Deficiencies 2

Question 1

What is the most common form of SCID ?

Answer 1

X-linked SCID

Question 2

Which cells are affected in X-linked SCID and why ?

Answer 2

Reduction in T and NK cells
Increase in premature B cells

Because Common gamma chain is mutated which is an important component of Cytokine receptors. Therefore cant respond to cytokines causing early cell arrest in T and NK cells. No IgA or IgG because CD4+ Th cells needed for Isotype switching.

Question 3

Which cells are affected in ADA deficiency SCID and why ?

Answer 3

Low T, NK and B cells

Adenosine deaminase enzyme is deficient which causes failure of lymphocyte maturation

Question 4

Why are infants with SCID protected in the first 3 months ?

Answer 4

maternal IgG is still present in the infants circulation and provides immunity

Question 5

What is the function of CD4+ T cells in the immune response ?

Answer 5

• activates B cells

- activates CD8+ cytotoxic T cells

Question 6

Which genetic syndrome causes the thymus to be underdeveloped and therefore a reduced number of T cells in children?

Answer 6

DiGeorge syndrome

T cell numbers recover with age

Question 7

List 4 pathologies of DiGeorge syndrome ?

Answer 7

CATCH 22

Cardiac abnormalities ( Tetralogy of fallot)
Abnormal facies (low set ears, high forehead)
Thymic aplasia (Reduced T cells)
Cleft palate
Hypocalcaemia (hypoparathyroidism)

22nd chromosome mutation 22q11

(There is developmental defect in the pharyngeal pouch)

Question 8

What causes a profound deficiency in CD4+ T cells but normal numbers of CD8+ T cells ?

What is the name of this syndrome ?

Answer 8

Absent expression of MHC class II molecules. (Means that T cells cant undergo affinity selection in the thymus to become CD4+)

Bare Lymphocyte syndrome -Type 2 (BLS type 2)

Question 9

Why do you get a reduction/absence in IgG and IgA immunoglobulins with CD4+ T cell defficiency (e.g in BLS type2) ?

Answer 9

The CD4+ T helper cells are involved in B cell Isotope switching so you have IgM B cells but cant switch to IgG/ IgA in the germinal centres.

Question 10

What is the definitive treatment of SCID and BLS type 2 ?

Answer 10

Haematopoeitic stem cell transplant

Question 11

How do you treat ADA SCID ?

Answer 11

Enzyme replacement therapy

Question 12

Which bacterial infection are patients with an IFN gamma deficiency particularly susceptible to ?

Answer 12

Recurrent Mycobacterium Marinum infections (atypical mycobacterium)

Question 13

22q 11.2 deletion syndrome is also known as ???

Answer 13

DiGeorge syndrome

Defect in the development of the pharyngeal pouch

Question 14

Is the IgM B cell response T cell dependent ?

Answer 14

No

Question 15

How do CD4+ T cells help B cells undergo B cell differentiation ?

Answer 15

CD40 ligand is expressed on CD4+ Th cells and this acts on CD40 receptors on B cells causing isotope switching.

Question 16

Which part of an Antibody identifies pathogens/toxins ?

Answer 16

Fab region

Question 17

Which part of an antibody interacts with Complement/phagocytes/NK cells ?

Answer 17

Fc region

Question 18

Which X-linked disease stops B cells leaving the bone marrow and hence is associated with a deficiency in mature B cells and antibodies ?

Answer 18

Bruton’s X linked agammaglobulinaemia

Question 19

Which X-linked syndrome is associated with failure of B cell maturation and isotype switching causing an elevated serum IgM but no IgG/IgA?

Answer 19

Hyper IgM syndrome

Mutation in CD40 ligand on T cells which means CD4+ T helper cells cant help B cells to undergo Maturation in germinal centres

Question 20

Which immune deficiency disease is associated with poor response to immunisation, with low IgG/ IgA / IgM ?

Answer 20

Common variable immune deficiency

Not much known but it is a defect in production of Immunoglobulins
They get a lot of inflammatory and auto-immune diseases

Question 21

Which immunodeficiency disease is associated with recurrent respiratory tract infections, low IgA levels and normal levels of all other immunoglobulins ?

Answer 21

IgA deficiency

Question 22

Which genetic mutation is associated with Wiskott-Aldrich syndrome ?

Answer 22

WASp gene

Question 23

Which mutation is associated with Bare lymphocyte syndrome type 2 ?

Answer 23

MHC class II

Question 24

Which mutation is associated with SCID ?

Answer 24

IL-2 receptor

Question 25

Which mutation is associated with Bruton’s X-Linked Agammaglobulinaemia ?

Answer 25

BTK gene

Question 26

Which lymphocytes respond to foreign HLA-DR types ?

Answer 26

CD4 + T cells

Question 27

Which lymphocytes respond to foreign HLA-B types ?

Answer 27

CD8+ T cells

Question 28

Patient presents with recurrent nose bleeds, easy bruising and blood in the stool. Blood tests reveal a thrombocytopenia, elevated IgA and IgE and reduced IgM levels.

Most likely diagnosis ?

Answer 28

Wiskott-Aldrich syndrome

Question 29

Patient presents with jaundice and hepatomegaly. His bloods show a low CD4+ T cell level but normal CD8+ level.

Most likely Diagnosis?

Answer 29

Bare lymphocyte syndrome Type 2

Question 30

Young girl presents with recurrent skin infections with a normal neutrophil count and a NTB test remains colourless

Most likely diagnosis ?

Answer 30

Chronic granulomatous disease.

Caused by a deficiency in NADPH which causes absence of the respiratory burst.