Negative Regulator Stops Extreme Immune Response to Parasite, Averting Multi-OrganDamage
Research at Osaka University identifies novel role for BATF2 protein in controlling immune response
to Chagas disease parasite infection, preventing immunopathology

Osaka – Cytokines are proteins secreted by several types of immune cells in response to infection,inflammation, or injury. Interleukin-17 (IL-17) is one such cytokine that causes inflammation, bycontrolling the production of other cytokines and mobilizing a type of white blood cell (neutrophil) thatfights infections. During some parasitic infections, host protection is achieved by an IL-17 response,
but too much IL-17 causes chronic tissue damage. This response is therefore tightly regulated byother cytokines, but the precise mechanisms were unclear.
Now, Japanese research coordinated by Osaka University has unraveled the complex network ofcytokine control that prevents multi-organ damage during infection by the protozoan parasite thatcauses Chagas disease.
Trypanosoma cruzi is an intracellular parasite that infects and destroys heart and digestive muscle,causing Chagas disease, which affects 6–7 million people worldwide mainly in endemic areas ofCentral and South America.
Previous work showed that T. cruzi infection in mice led to production of the cytokine IL-23 by hostimmune cells. This promoted the generation of CD4+ T cells that produce IL-17. Researchers built onthese findings by focusing on the protein BATF2, which they found in an earlier study to be switchedon by cytokine signaling in innate immune cells derived from bone marrow during T. cruzi infection.
To study the role of BATF2 in this process, the team generated mice lacking the gene encoding thisprotein. These Batf2 knockout mice produced much more IL-17 in response to the parasite than didcontrol mice. They also produced more IL-23, suggesting that BATF2 normally suppresses expressionof the Il23a gene. However, it was not shown to be required for the killing of T. cruzi.
“When we infected both Batf2 knockout and control mice with the same amount of T. cruzi, theknockout mice had a lower number of parasites and improved survival, probably because ofincreased IL-17 levels,” say Hisako Kayama co-author of the report on the study. “Yet, despite this,the extent of immune activation and tissue damage was more severe (Figure 1).”Further analysis of protein–protein interactions revealed that BATF2 interacts directly with atranscription factor to inhibit Il23a expression (Figure 2).
“This novel function of BATF2 prevents the excessive IL-17 response that would otherwise cause
immunopathology during parasitic infection,” corresponding author Kiyoshi Takeda explains. “We also
think that this negative regulation is not unique to T. cruzi infection, but that it likely occurs in othermodels of infection because BATF2 is expressed in several different cell types.”

Article Information
Title: “BATF2 inhibits immunopathological Th17 responses by suppressing Il23a expression during
Trypanosoma cruzi infection”
Authors: Shoko Kitada, Hisako Kayama, Daisuke Okuzaki, Ritsuko Koga, Masao Kobayashi, Yasunobu

Arima, Atsushi Kumanogoh, Masaaki Murakami, Masahito Ikawa, and Kiyoshi Takeda
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Journal: The Journal of Experimental Medicine
Funded by: Japan Society for the Promotion of Science

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