Anthrax toxin curbs immune cells

Scientists have revealed yet another way in which the bacterium that causes anthrax disarms the immune system.

The microbe, Bacillus anthracis, produces a molecular complex that’s called lethal toxin known to interrupt a cascade of signals inside macrophages, the immune cells that envelop and destroy bacteria (SN: 5/9/98, p. 299). This interference kills the macrophages.

The toxin also interrupts the same signaling cascade in dendritic cells, another class of immune cells, Bali Pulendran of the Emory Vaccine Research Center in Atlanta and his coworkers report in the July 17 Nature. Dendritic cells are crucial to an immune response since they alert antibody-producing cells and other protective cells to the presence of dangerous microbes.

Pulendran’s team found that, unlike macrophages, dendritic cells exposed to the anthrax toxin don’t die. However, the cells can no longer stimulate the activity of other cells of the immune system. Injections of the toxin into mice confirmed that it suppresses dendritic-cell function.

The investigators speculate that the anthrax toxin could be modified into a drug that dampens immune responses. Such a drug might alleviate autoimmune disorders or prevent transplanted organs from being rejected.


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