learning outcomes

Question 1

Define primary immune deficiency

Answer 1

• disorders in which part of the body’s immune system is missing or does not function normally
• predisposes to infections, cancers, autoimmunity
• most primary immunodeficiencies are genetic disorders

Question 2

Define secondary immune deficiency

Answer 2

the cause of the immune deficiency is secondary in nature (i.e. caused by other disease, drug treatment, or environmental exposure to toxins

Question 3

explain the classification of primary immune deficiency disorders

Answer 3

• mutations: severe combined immunodeficiency (SCID)
• polygenic: common variable immunodeficiency (CVID), IgA deficiency, specific antibody deficiency
• autoimmunity: autoimmune polyendocrinopathy candidiasis ectodermal dysplasia (APECED)

Question 4

Give examples of primary disorders of T cell, B cell, phagocyte and complement function

Answer 4

defects in T cells: infection with intracellular organisms (protozoa, herpes. candida, and mycobacteria)

phagocytes: infections with staphylococci, gram-negative bacteria, and fungi
complement: meningitis

Question 5

Understand the causes of primary immunodeficiency

Answer 5

mutations: permanent alteration in the DNA sequence that makes up
a gene

polymorphisms: variation at a single base pair
polygenic: disorders caused by the combined action of more than one gene

Question 6

Illustrate the complications of immune deficiency disorders

Answer 6

mutations: SCID
- die in the first few months of life unless treatment is given
- history of early deaths in maternal uncles

polymorphism

• human leukocyte antigen (HLA) alleles can affect the outcome of infections
• mannan-binding lectin (MBL) (collagen-like protein that binds sugars in bacterial cell walls) activates the classic complement pathway

polygenic:
- CVID: low levels of total IgG. Levels of IgA and IgM and numbers of B and T cells are variable; causes recurrent respiratory tract infections
- specific antibody deficiency: develop recurrent infections with pneumococcus or Haemophilus spp. despite normal total IgG.

Question 7

list the clinical features of primary immunodeficiency

Answer 7

unusual or recurrent infection

diarrhoea, unusual rashes

Question 8

understand the principles of the treatment of primary immunodeficiency