Immune dysfunction

Question 1

Primary immunodeficiency disorders

Answer 1

• most likely hereditary
• due to genetic or developmental defects in the immune
  system
• usually present at birth
• become evident during infancy or childhood
• > 100 disorders but are relatively rare

Question 2

Secondary immunodeficiency disorders

Answer 2

• results from damage to otherwise normal components
• develop later in life
• more common than primary immunodeficiency
  disorders
• some disorders shorten life span others persist
  throughout life but do not affect life span
• few resolve with or without treatment

Question 3

Cause of immunodeficiency

Answer 3

- primary cause
   \+ genetic
- secondary cause
   \+ acquired infections
   \+ chronic diseases
   \+ medication or therapy
   \+ physical state

Question 4

Type I hypersensitivity

Answer 4

• antibody mediated
  + rapid onset - within minutes
  + short-term
  + antigens
  + activates B cells to secrete antobodies
  + normal antibody secretion is IgG or IgM but with
  allergy IgE is secreted
  + two phases: sensitisation and effector
  + result in the secretion of activators such as histamine

Question 5

Type II hypersensitivity

Answer 5

• antibody mediated/cellular destruction
  + onset within hours
  + IgM and IgG mediated
  + particulate antigens: cell/matrix associated or cell
  surface receptor
  + induce direct cellular lysis (complement mediated)
  + enhanced phagocytic activity

Question 6

Type III hypersensitivity

Answer 6

• antibody mediated/immune complex formation
  + 3-8hours
  + antibodies bind to soluble Ags forming circulating
  immune complexes that deposit on various tissue

Question 7

Type IV hypersensitivity

Answer 7

- T cell mediated
   \+ delayed: 1-3 days to appear
   \+ T cells secrete cytokines
   \+ effector phase generally peaks 48-72 hrs after 
      exposure
   \+ granuloma formation

Question 8

Determinants of autoimmunity

Answer 8

1. Geographical location
2. Ethnicity/genetics
3. Environmental triggers
4. Age