11 Immunodeficiency

Question 1

What is immunodeficiency?

Answer 1

Clinical situation where the immune system is not effective enough to protect the body against infection.

Question 2

Name some common causes of secondary immunodeficiency.

Answer 2

Stress, surgery, burns, malnutrition, cancer, immunosuppressive drugs, irradiation, AIDS, measles, TB.

Question 3

What causes immunodeficiency of the innate immune system? How does it present?

Answer 3

IRAK deficiency. Leads to IL1, IL6 + TNF release.

Recurrent infection at young age with CRP that isn’t elevated.

Question 4

How does IRAK deficiency change clinically over time?

Answer 4

Gets less serious as adaptive immune system develops to cover the gaps.

Question 5

How does phagocytosis work?

Answer 5

Free radical generation lowers the pH in the lysozyme, activating proteolytic enzymes which kill phagocytksed bacteria.

Question 6

Which test tests for the oxidative response seen in phagocytosis?

Answer 6

Nitroblue tetrazolium test (NBT).

Question 7

Which disease develops when phagocytosis is ineffective?
5 characteristic signs.
What is its genetic basis?

Answer 7

Chronic granulomatous disease.
Osteomyelitis, pneumonia, swollen lymph, granulomas, IBD.
X-linked gp91 mutation.

Question 8

An absent terminal complement pathway response predisposes you to which disease?

Answer 8

Meningococcal meningitis.

Question 9

What is X-linked agammaglobulinaemia? How does it present? How is it treated?

Answer 9

Loss of antibody secretion, leading to recurrent pyogenic bacterial infections (sino-pulmonary). Not diagnosed until 1-2yrs due to maternal IgG presence. Treated with antibiotics and iv IgG for life.

Question 10

Name 6 primary B cell deficiencies.

Answer 10

Common Variable Immunodeficiency. 
X-linked agammaglobulinaemia.
Autosomal recessive Hyper IgM syndrome.
IgA Deficiency.
IgG Subclass Deficiency.
Transient Hypogammaglobulinaemia of infancy

Question 11

How do Severe Combined Immunodeficiency (SCID) syndrome present? (3)

Answer 11

Recurrent opportunistic infections - commonly:
Extensive oro-phayngeal candida.
Protozoa: pneumocystitis.
Fulminant chickenpox with haemorrhagic lesions.

Question 12

What is SCID? How is it treated?

Answer 12

Defects in T cells, worse than B cell deficiencies as B cells need T cell help.
Bone marrow transplant.

Question 13

What does Adenosine Deaminase Deficiency (ADD) cause?

Answer 13

SCID.

Question 14

Name three causes of CID (less severe than CID).

Answer 14

Purine Nucleoside Phosphorylase Deficiency.
MHC Class II Deficiency.
Wiskott-Aldrich Syndrome.