Infection in the immune-compromised host

Question 1

Define Immunodeficiency

Answer 1

A failure to achieve immune function to provide efficient, self-limited host defence against the biotic and abiotic environment whilst preserving tolerance to self

Question 2

Features of innate immunity

Answer 2

• Early response
• Limited specificity
• Generalised

Question 3

Components of innate immunity

Answer 3

• Barriers (eg skin, tears, GI tract)
• Phagocytes, neutrophils, macrophages
• NK cells and mast cells
• Complement and other proteins

Question 4

Features of adaptive immunity

Answer 4

• Later response
• Variable
• Highly specific and ‘remembers’ infection

Question 5

Components of adaptive immunity

Answer 5

• APCs present Ag to T cells
• Activated T cells provide help to B cells and kill abnormal and infected cells
• B cells - produce antibody specific for antigen

Question 6

Congenital reasons for immunodeficiency (groups, not specifics)

Answer 6

• B and T cell deficiencies (DiGeorge; SCIDS)
• Macrophage and cytokine defects
• Phagocyte deficiency/dysfunction (chronic granulomatous disease; hyper IgE)
• Complement deficiencies
• Other (Trisomy 21 (Down’s); asplenia)

Question 7

Management of immunocompromised host with an infection

Answer 7

• Thorough history
• Screen for likely sources (eg CXR)
• Blood cultures
• Fast antibiotics: IV, broad spectrum, gram negative and atypical cover (broad spectrum B-lactam + aminoglycoside eg taz + gent)
• Frequent reassessment

Question 8

Protecting immunocompromised people

Answer 8

• Physical separation, preferably positive pressure room
• Reverse barrier nursing
• Minimal contact
• Strict hand hygiene
• Charts outside room