CCR5-DELTA 32

CCR5: 

• What is it? Cysteine-cysteine chemokine receptor 5 (CCR5) is a protein on the surface of white blood cells that is involved in the immune system as it acts as a receptor for chemokines. 
  
  
• Prevalence: 
  • CCR5 is found in the cell membranes of many types of mammalian cells, including nerve cells and white blood cells. 
    
    
  • In humans, the CCR5 gene that encodes the CCR5 protein is located on the short (p) arm at position 21 on chromosome 3. 
    
    
  
  
  
• Role: The role of CCR5 is to allow entry of chemokines into the cell—chemokines are involved in signalling the body’s inflammation response to injuries. 
  
  

CCR5-delta 32: 

• Various mutations of the CCR5 gene are known that result in damage to the expressed receptor. 
  
  
• One of the mutant forms of the gene is CCR5-delta 32, which results from deletion of a particular sequence of 32 base-pairs. 
  
  
• This mutant form of the gene results in a receptor so damaged that it no longer functions. But surprisingly, this does not appear to be harmful. Moreover, this mutation can be advantageous to those individuals who carry it. 
  
  
• The virus HIV normally enters a cell via its CCR5 receptors, especially in the initial stage of a person becoming infected. But in people with receptors crippled by the CCR5-delta32 mutation, entry of HIV by this means is blocked, providing immunity to AIDS for homozygous carriers and greatly slowing progress of the disease in heterozygous carriers. 
  
  
• Up to 20% of ethnic western Europeans carry this mutation, which is rare or absent in other ethnic groups. This suggests that the CCR5-delta32 mutation was strongly selected for some time during European history.