Immunodeficiency

Question 1

What are the general principles of an immune response?

Answer 1

• Self-regulation
• Limitation of host damage
• Adaptive responses to changing pathogen
• Multilayer defense
• Multiple mechanisms of pathogen clearance
• Main physiological functions to protect from infection
• Network of pathogen recognition
• Effective inter-cellular communication

Question 2

What are the functions of lymphocytes?

Answer 2

• B lymph= Potential to secrete antibodies: humoral immunity
• Killer/cytotoxic T= Able to kill: cellular immunity
• Helper T= Secrete growth factors (cytokines) which control immune response: Help B lymph
• Suppressor T= dampen down immune response

Question 3

How can antibodies bind to antigens to inactivate them?

Answer 3

• Agglutination of microbes
• Neutralisation
• Precipitation of dissolved antigens
• Activation of complement system

Question 4

How do cytotoxic T cells kill infected cells?

Answer 4

1) Cytotoxic T cells bind to infected cell
2) Perforin makes holes in infected cell’s membrane & enzymes enter promoting apoptosis
3) Infected cell is destroyed

Question 5

What is immunodeficiency?

Answer 5

Clinical situation where immune system is not effective enough to protect body against infection. Occurring at any age

Question 6

What are the causes of immunodeficiency?

Answer 6

• Secondary to effects of external factors

- Some primary immunodeficiencies caused by genetic defects in individual components of immune system

Question 7

What are the causes of secondary/acquired immunodeficiencies

Answer 7

• Stress
• Surgery/burns
• Malnutrition
• Cancer (esp lymphoproliferative disease)
• Immunosuppressive effects of drugs inc cancer therapy
• AIDS
• Irradiation
• Other infections (measles, TB)

Question 8

What are complications & types of Chronic granulomatous Disease (CGD)?

Answer 8

C=Osteomyelitis, Pneumonia, Swollen lymph nodes

T=Ginigivitis, Non-malignant granulomas, Inflammatory bowel disease

Question 9

Describe defects in B cells, What do they usually lead to?

Answer 9

• Different degrees of loss of antibody secretion
• Recurrent bacterial infection with pyogenic organisms
• Most very serious
• Usually diagnosed around 1-2years since maternal IgG protects

Question 10

Name some primary B-cell deficiencies?

Answer 10

• X-linked agammaglobulinaemia
• IgA deficiency
• IgG subclass deficiency
• Transient hypogammaglobulinaemia of infancy
• Autosomal recessive hyper IgM syndrome
• Common variable immunodeficiency

Question 11

Describe defects in T cells

Answer 11

• More dramatic since B cells also need T cell help
• Symptoms are recurrent infection with opportunistic infections, viruses, bacteria, fungi (candida), protozoa (pneumocystis)

Question 12

What does a defect in both B & T cells lead to?

Answer 12

Severe combined immunodeficiency syndromes (SCID)

Question 13

Name some primary T-cell deficiencies

Answer 13

• SCID
• Adenosine deaminase deficiency
• Purine Nucleoside Phosphorylase deficiency
• MHC class II deficiency
• Wiskott-Aldrich syndrome