Register for an account

X

Enter your name and email address below.

Your email address is used to log in and will not be shared or sold. Read our privacy policy.

X

Website access code

Enter your access code into the form field below.

If you are a Zinio, Nook, Kindle, Apple, or Google Play subscriber, you can enter your website access code to gain subscriber access. Your website access code is located in the upper right corner of the Table of Contents page of your digital edition.

Health

Why We Get Diseases Other Primates Don't

New research might explain why HIV kills only humans.

Newsletter

Sign up for our email newsletter for the latest science news

Last March the German biotech company TeGenero began testing the drug TGN1412 on human volunteers. The result was one of the most disastrous clinical trials in history. Although TGN1412 is harmless to other primates at high doses, it sent the immune systems of six people into near-deadly overdrive, causing widespread inflammation and multiple-organ failure.

Two months later hematologist Ajit Varki of the University of California at San Diego published a paper offering a plausible explanation for why things went so wrong. The drug hit humans so much harder, he says, because of a difference in the surface molecules of our white blood cells. Varki studies siglecs, small groups of receptors that thickly stud the immune T cells of monkeys and apes but are few and far between in humans. Siglecs act as brakes, stopping the immune system from overreacting. Because human T cells don't have as many of these brakes, our cells are a hundred times more aggressive than those of chimps when faced with drugs like TGN1412, which work by triggering the immune system.

Why the difference? Sometime after humans branched from apes, "we may have faced some terrible pathogen," Varki speculates. "By removing these brakes we may have done better then." An overreactive immune system helps fend off infections, but it could also explain why we suffer from immune-system diseases like bronchial asthma, chronic hepatitis, and type I diabetes, which don't affect chimps. Overactive T cells are also a factor in AIDS, points out Varki, which may help explain why HIV, which evolved in chimps, kills only humans.

2 Free Articles Left

Want it all? Get unlimited access when you subscribe.

Subscribe

Already a subscriber? Register or Log In

Want unlimited access?

Subscribe today and save 75%

Subscribe

Already a subscriber? Register or Log In