Radio Shows | Malaria and the DARC Mutation | mp3 … wma … wav
You may know some people are born with sickle cell disease, but did you know it was an evolutionary response to another life threatening illness?
That's right. Human evolution actually created sickle cells in order to survive malaria - a disease that has co-existed with man for at least ten thousand years.
People with sickle cell disease don't always have round red blood cells. Instead, theirs are sometimes shaped like a sickle, or crescent which doesn't allow them to pass through certain small capillaries. That creates serious health problems like stroke and damage to certain organs.
The flip side is these sickle-shaped cells are resistant to malarial parasites which need red blood cells to replicate and survive. The sickle shaped cells have a much shorter life span than normal red blood cells so the parasites don't have enough time to replicate.
That's useful for surviving malaria but consider that people with sickle cell disease only live into their forties. And now scientists have found another downside to this evolution.
It's a mutation that while making nearly all African Americans resistant to one type of malaria, leaves them more susceptible to HIV infection.
That's because the mutation results in less of a protein called DARC which is found on the surface of red blood cells.
Without DARC the malarial parasites do not recognize red blood cells which means they can't invade them to replicate and survive.
But the lower production of DARC also increases the body's number of T-cells - just the type of cells HIV likes to invade and replicate in.
Here's yet another twist: This very mutation which makes African Americans more susceptible to HIV, also increases the survival of these HIV patients by an average of two years.
The new discovery may at least in part explain the high prevalence of HIV in sub-Saharan Africa.
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