Toxoplasma gondii is best known as the parasite that may lurk in a cat's litter box. Nearly a third of the world's population is believed to live with a chronic Toxoplasma infection. It's of greatest concern, however, to people with suppressed immune systems and to pregnant women, who can pass the infection to their fetuses.
Toxoplasma's "success," scientists believe, owes in part to its ability to evade the immune response of its host, whichever warm-blooded vertebrate it has infected. Now a new study suggests the parasite employs a sophisticated manipulation to suppress that immune response.
Work - Researchers - Penn - School - Veterinary
The work, led by researchers from Penn's School of Veterinary Medicine and the University of Arizona and published in the Journal of Experimental Medicine, shows that T. gondii parasites inject their host's macrophages, a type of immune cell, with a protein that changes the activity of the macrophage itself, creating what is known as an M2 macrophage. Those changes, the team showed, rein in the response of T cells that are normally responsible for killing parasites.
"This is the first time that it's been shown that injection alone is sufficient to drive the creation of M2 macrophages," says Christopher A. Hunter, an immunologist at Penn Vet and senior author of the paper. "Pharmaceutical companies have been targeting the pathways that create M2 macrophages for a long time because they're very important in wound healing, fibrosis, lung repair, and so on. But here's a parasite that manages to target it perhaps more efficiently than pharma has been able to."
Ability - Parasite - Host - Cell - Populations
As the ability of the parasite to affect the infected and injected host cell populations has an impact on the course of infection, Hunter hopes further studies will help define the underlying mechanism.
For T. gondii, infection is a careful balancing act. It wants to spread far and wide within a host—and...
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