Immunology - T Cell Disorders

Question 1

What are some examples of T cell disorders?

Answer 1

DiGeorge Syndrome
Purine Nucleoside Phosphorylase Deficiency
Wiskott-Aldrich Syndrome
Ataxic Telangiectasia
AIDS

Question 2

What causes DiGeorge Syndrome?

Answer 2

AKA 22q11.2 deletion syndrome

Results from a microdeletion in part of chromosome 22

Question 3

What does the microdeletion in DiGeorge Syndrome lead to?

Answer 3

Leads to a developmental defect in the third pharyngeal pouch and third branchial cleft this leads to incomplete thymus development

Inability to create T cells

Question 4

What are the features of DiGeorge Syndrome?

Answer 4

CATCH-22

Congenital heart disease
Abnormal facies (characteristic facial appearance)
Thymus incomplete development
Cleft palate
Hypoparathyroidism - Hypocalcaeima
22nd chromsome affected

Question 5

What is Purine nucleoside phosphorylase deficiency? (PNP)

Answer 5

Autosomal recessive condition

PNPase- enzyme that helps breakdown purines

Without PNPase, dGTP builds up

dGTP is exclusively toxic to T cells

Question 6

What does purine nucleoside phosphorylase deficiency lead to?

Answer 6

Increased levels of dGTP

Causes low T-lymphocytes levels
Normal B cells and immunoglobulins

Question 7

What happens to patients immunity in PNP?

Answer 7

Gradually gets worse

Increasingly susceptible to infections particularly viruses and live vaccines

Question 8

What is Wiskott-Aldrich syndrome? (WAS)

Answer 8

X-linked recessive condition
Mutation on the WAS gene

Causes abnormal functioning T cells

Question 9

What are the features of WAS?

Answer 9

Thrombocytopenia
Immunodeficiency
Neutropenia
Eczema
Recurrent infections
Chronic bloody diarrhoea

Question 10

What is ataxic telangiectasia?

Answer 10

Autosomal recessive condition affecting gene coding for ATM serine/threonine kinase protein on Chromosome 11

Question 11

What does the ATM serine/threonine kinase protein do?

Answer 11

Important in several functions of DNA coding

Mutation in this gene leads to problems coding for other genes

Question 12

What are some features of Ataxic telangiectasia?

Answer 12

• Low T cells and immunoglobulins
• Ataxia - cerebellar impairment
• Telangiectasia - particularly in the sclera
• Predisposition to cancers - particularly heamatologoical
• Slow growth and delayed puberty
• Accelerated ageing
• Liver failure