Taking a toll on parasitic infections

In 1997, a blockbuster article by two Yale scientists, the late Charles A. Janeway Jr., M.D., and Ruslan M. Medzhitov, Ph.D., professor of immunobiology, kicked off one of the hottest research areas in immunology. Janeway and Medzhitov reported that innate immune system molecules called toll-like receptors, or TLRs, give early warning of microbial or viral invaders to the acquired immune system, which marshals the body’s array of defenses against infection.

Scientists have since identified over a dozen types of TLRs, which work by detecting distinctive genetic signatures or proteins found in bacteria and viruses but not in the eukaryotic cells that make up our bodies.

But some pathogens—such as Toxoplasma gondii (right), the parasite that causes toxoplasmosis—are also eukaryotes, and a team at Yale and the National Institutes of Health wondered whether TLRs could recognize them.

In the June 10 issue of the journal Science, the group reported that TLR11, discovered at Yale in mice just last year, detects a protein in T. gondii and triggers a robust immune response.

The global impact of parasitic infections such as toxoplasmosis is tremendous. Sankar Ghosh, Ph.D., professor of immunobiology and a member of the research team, says that while it is not yet clear whether humans have a functional version of TLR11, “insight obtained from these studies should lead to development of novel strategies to combat these infections.”