Exam 2: Immunocompromised Host

Question 1

High Risk Groups

Answer 1

• Organ transplant recipients
• Cancer chemotherapy recipients
• AIDS patients
• Certain chronic diseases
• Chronic corticosteroid use
• The elderly
• The very young

Question 2

Transplant Recipient

Exposures

Answer 2

Exposure falls into 4 overlapping categories:

1. Donor derived
   
   • Pathogens usually reside within lymphocytes
   • Ex. Cytomegalovirus (CMV)
2. Recipient derived
   
   • Ex. CMV, MTb, Toxoplasma
3. Nosocomial
   
   • Ex. MRSA, Aspergillus, Candida
4. Community
   
   • Ex. Pseudomonas, Cryptococcus

Question 3

Immunocompromise

Types

Answer 3

Primary ⇒ genetic

Secondary ⇒ acquired

Question 4

Cell-Mediated Immunity (CMI)

Deficiency

Answer 4

• CD4⁺ T_H cells control every aspect of CMI
  
  • Via differential secretion of cytokines
  • Including activation of Mφ and CTLs
• Deficits creates the most severely compromised patients

Question 5

Neutropenia

Answer 5

• PMNs patrol mucosal surfaces
• Deficits promotes invasion of resident flora and opportunists

Question 6

Increased Susceptibility

Answer 6

↓ CMI or neutropenia ⇒ ↑ predisposition, infection, or reactivation

• Primary & opportunistic pathogens
  
  • Fungi
    
    • Candida, Pneumocystis
  • Intracellular bacteria
    
    • Mycobacterium, Listeria
  • Viruses
    
    • CMV, Herpes
  • Intracellular parasites
    
    • Toxoplasma
• May be more difficult to recognize infection clinically
• Susceptibility to different pathogens changes with degree of immunocompromise

Question 7

Risk Assessment

Answer 7

• Donor screening
• Recipient screening
• Post-transplant screening and monitoring

Question 8

Prevention Strategies

Answer 8

• Vaccination
• Lymphocyte depletion in grafts prior to transplant
• Chemoprophylaxis
• Preemptive therapy
• Lifestyle changes
• Reduce immunosuppresion if possible