Anthrax Toxin Sabotages the Immune Response

Researchers have found that anthrax lethal factor (LF) impairs the function of dendritic cells and thereby diminishes the immune system's ability to battle the microbe.

Investigators at Emory University (Atlanta, GA, USA) studied the effect of LF on immune dendritic cells rather than on macrophages as had been done previously. They reported in the July 17, 2003, issue of Nature that dendritic cells exposed to LF and then stimulated with lipopolysaccharide did not upregulate co-stimulatory molecules, secreted greatly diminished amounts of proinflammatory cytokines, and did not effectively stimulate antigen-specific T-cells in vivo. Furthermore, injections of LF induced a profound impairment of antigen-specific T- and B-cell immunity.

"This is the first study that demonstrates any interaction between Bacillus anthracis and dendritic cells,” explained senior author Dr. Bali Pulendran, associate professor of pathology at Emory University. "Our findings reveal a novel mechanism of action by which the microbe targets the host-immune reaction. When a person is infected with a microbe, we count on the immune system to begin fighting the foreign substance immediately. When the dendritic cells are compromised, such as in our study with the anthrax lethal factor, the innate immune system is unable to stimulate the immune response, thus permitting the microbe to spread unchecked.”




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