Malaria immune evasion

Tara Smith of Aetiology has a fascinating post on gene switches in malaria.

Here's an excerpt:

A question asked is how does P. falciparum regulate expression of the var gene family, a highly polymorphic family of genes which encode the P. falciparum erythrocyte membrante protein 1(PfEMP1). PfEMP1 is a major virulence factor that plays a role in immune evasion. In each individual P. falciparum parasite, only one var gene is expressed; the other 59 are silent. However, the parasite can switch expression: a parasite that initially expresses, say, var29 can switch and later express only var 40, for instance. This would protect the parasite, as a host that was mounting an immune defense targeted to the protein produced by var29 would have to essentially start back at square one. This was previously known, but what wasn't known was just how P. falciparum carries out this switching, and more importantly, just how it keeps the other 59 silent while expressing the one of choice.

She answers the question, and illuminates a lot about how P. falciparum manages to steer clear of immune defenses -- I mean, literally steer red blood cells around.

Parasites. To paraphrase Elwood Blues: I hate those guys.