Primary Immunodeficiency 2

Question 1

Outline the life cycle of a T lymphocyte.

Answer 1

1. Produced from stem cells in the bone marrow.
2. Naive T cells exported to thymus, selection takes place
3. Mature T cells travel to lymphoid tissue and follicles, where they reside.

Question 2

Two main classifications of T cells?

Answer 2

1. CD4+

2. CD8+= Cytotoxic T cell

Question 3

Function of CD4+ cells?

Answer 3

1. Immunoregulatory functions
   - Stimulate CD8 & B cells
   - Produce cytokines
2. Recognise peptides on MHC class II molecules

Question 4

Function of CD8+ cells?

Answer 4

1. Recognise peptides on MHC class I molecules
2. Directly kill pathogens via perforin release
3. Important in viral and tumour defence

Question 5

What are the functions of B lymphocytes? (2)

Answer 5

Antibody production & presentation

Question 6

What are the two types that B cells differentiate into?

Answer 6

1. Memory B cells

2. Plasma cells that produce antibodies

Question 7

Functions of antibodies? (4)

Answer 7

1. Identify pathogens
2. Stimulate other components of immune system (complement, NK, phagocytes)
3. Neutralise toxins
4. vital for Bacterial infection defence

Question 8

What is reticular dysgenesis?

Answer 8

Defect of haemopoetic stem cells which causes lack of production of

• Neutrophils
• Macrophages
• Lymphocytes
• Platelets

Fatal if not corrected with bone marrow transplant

Question 9

What happens in severe combined immunodeficiency (SCID)?

Answer 9

Failure to produce lymphocytes

Question 10

Some common clinical presentations of SCID?

Answer 10

1. Recurrent infections
2. Persistent diarrhoea
3. Failure to thrive
4. Unusual skin disease (graft vs host disease)

Dont get acutely unwell until 3 months of age because of maternal IgG in colostrum

Question 11

What is the commonest form of SCID? (genetic)

Answer 11

X linked

Question 12

What is the result of X linked SCID?

Answer 12

IL2 mutation

• Failure to produce T cells
• Immature B cells produced

Question 13

Treatment for SCID?

Answer 13

1. Prophylactic- Antibiotics, antifungals, IV immmunoglobin.

2. Definitive- stem cell transplant

Question 14

SCID is suitable for gene therapy. T/F?

Answer 14

True

Question 15

What happens in Digeorge syndrome?

Answer 15

Failure in thymic development- Developmental defect of 3/4th pharyngeal pouch

Question 16

What are the clinical features of Digeorge’s? (5)

Answer 16

1. Congenital heart defects
2. Cleft palate
3. T lymphopenia
4. Hypothyroidsim & hypocalcaemia
   5 Psychiatric disorders, developmental delay

Question 17

Digeorge’s is caused due to a deletion at chromosome 22q11. T/F?

Answer 17

True

Question 18

Digeore syndrome makes someone susceptible to what?

Answer 18

Recurrent infections- bacterial, fungal and viral

Question 19

What do investigations reveal in Digeorge? (immune cell count)

Answer 19

1. Absent or low T cell count
2. Normal/High B cell- Low IgG, E, A
3. Normal NK

Question 20

Management Digeorge’s?

Answer 20

1. Correct metabolic/cardiac issue
2. Prohylactics
3. Aggressive antibiotics
4. Ig replacement therapy

Question 21

What are the disorders of T Cell effector functions?

Answer 21

1. Cytokine production
2. T-B cell communication
3. Cytotoxicity

Question 22

What are the two main T cell effector disorders?

Answer 22

1. IL12 Deficiency

2. IFNy deficiency

Question 23

Clinical presentations of T cell effector disorders? (3)

Answer 23

1. Recurrent infections- TB, atypical mycobacteria, BCG, aspergillus
2. Malignancies at young age
3. Autoimmune diseases

Question 24

What are the investigations for T cell deficiencies?

Answer 24

1. 1st line
   - WBC
   - Serum immunoglobins, protein electrophoresis
   - Quantify sub lymphocyte numbers
2. 2nd line
   - Test T cell activation & proliferation
   - Additional lymphocyte lineage test
   - HIV test

Question 25

What happens in Brutons X linked hypogammaglobulinaemia?

Answer 25

Failure to produce mature B cells - No circulating B cells - No plasma cells - no circulating antibody after 1st 6 months

Question 26

What is Selective IgA deficiency?

Answer 26

No IgA produced. Increases risk of coeliac disease 10x. Usually asymptomatic

Question 27

What happens in common variable immunodeficiency? (CVID)?

Answer 27

Low IgG, IgE, IgA.

Question 28

Clinical features of CVID?

Answer 28

1. Recurrent bacterial infections 2. Autoimmune disease 3. Granulomatous disease

Question 29

Investigations for B cell deficiencies?

Answer 29

Same as T cell - WBC - Serum Ig, protein electrophoresis - Quantify T cell & B cell levels - Specific antibody responses to pathogens

Question 30

Management for B cell deficiencies?

Answer 30

1. Aggressive antibiotics 2. Antibody replacement therapy 3. Stem cell transplant