Disease-causing microbes like the food-borne bacterium Listeria monocytogenes specialize in invading and replicating inside their animal hosts' own cells, making them particularly tricky to defeat. Now, a new study led by biologists at the University of California, Berkeley, has identified a molecular alarm system in which the intracellular pathogen sends out signals that kick the immune response into gear.

Recent studies have shown that HIV causes a vigorous and prolonged immune response that eventually leads to the exhaustion of key immune system cells--CD4+ and CD8+ T-cells--that target HIV. These tired cells become less and less able to fight the virus, and the cells' fatigue contributes to the inability of an HIV-infected person's immune system to clear the virus from the body.

Six-thousand year old bones excavated in Jericho may help a joint Israeli-Palestinian-German research group combat tuberculosis.