Immune System

Knut the polar bear, the global sensation that captured the public imagination, died of an autoimmune disorder that caused his immune system to attack his brain.

Antibiotic-resistant bacteria may be tougher superbugs than previously thought: Not only are these bacteria harder to treat, they appear to be "fitter" in general.

A woman in Washington state is the first person to die of measles in the United States in a dozen years, but how did doctors miss her diagnosis.

The swine flu vaccine was linked with an increase in narcolepsy cases in Europe, and now researchers may have figured out why.

In the hopes of achieving a fuller buttocks, some women receive illegal injections of silicone that can cause a host of health complications.

Having an infection so severe that you have to be hospitalized may affect your IQ, a new study suggests.

Some human genes have activity levels that vary with the seasons, a new study shows.

Infants who start eating solid foods later than usual may be at increased risk for a type of blood cancer, a new study suggests.

Researchers found that animals with more copies of certain genes -- which are involved in fighting inflammation -- have longer life spans.

A woman in Oregon who received the yellow fever vaccine developed a rare and ultimately fatal reaction to the shot, according to a new report of the case.

People who drink four cups of joe daily have a lower risk of developing the debilitating disease multiple sclerosis (MS), researchers say.

Animations like this one, which shows HIV infecting a human cell, are helping researchers probe complicated, dynamic molecular interactions.

Fat cells just under a person's skin may be the first responders to invading bacteria, buying time until the white blood cells arrive at a wound site, according to a new study.

Smoking cigarettes is linked to the disappearance of the Y chromosome in the blood — a side effect that might explain why men who smoke are at greater risk for cancer than women who smoke.

A new study has found potential early markers for hemorrhagic fever diseases similar to Ebola, suggesting it may be possible to screen for these diseases much earlier.

Statins should be considered as a possible treatment for Ebola, some researchers argue.