Principal Features of Selected CD molecules

Question 1

CR1 (CD35)

Answer 1

• Principal cells:
  
  • Granulocytes
  • monocytes
  • erythrocytes
  • B cells
  • Follicular dendritic cells,
  • some T cells
• Principal cell functions:
  
  • binds C3b and C4b
  • promotes phagocytosis of C3b- or C4b- coated particles and immune complexes
  • regulates complement activation

Question 2

CR2 (CD21)

Answer 2

• Principle cells:
  
  • Mature B cells
  • Follicular dendritic cells
• Principle cells
  
  • Receptor for complement fragment C3b
  • Forms a coreceptor complex with CD19 and CD81 that delivers activating signals in B cells
  • Receptor for Epstein-Barr virus

Question 3

CR3 (Mac-1, CD11b)

Answer 3

• Principle cells
  
  • Granulocytes
  • Monocytes
  • macrophages
  • dendritic cells
  • NK cells
• Principle functions
  
  • Phagocytosis of iC3b coated particles
  • neutrophil and monocyte adhesion to endothelium (binds CD54) and extracellular matrix proteins