AUTHOR=Sajiki Yamato , Konnai Satoru , Goto Shinya , Okagawa Tomohiro , Ohira Kosuke , Shimakura Honami , Maekawa Naoya , Gondaira Satoshi , Higuchi Hidetoshi , Tajima Motoshi , Hirano Yuki , Kohara Junko , Murata Shiro , Ohashi Kazuhiko 

TITLE=The Suppression of Th1 Response by Inducing TGF-β1 From Regulatory T Cells in Bovine Mycoplasmosis

JOURNAL=Frontiers in Veterinary Science

VOLUME=7

YEAR=2020

URL=https://www.frontiersin.org/journals/veterinary-science/articles/10.3389/fvets.2020.609443

DOI=10.3389/fvets.2020.609443

ISSN=2297-1769

ABSTRACT=<p>Regulatory T cells (Tregs) regulate immune responses and maintain host immune homeostasis. Tregs contribute to the disease progression of several chronic infections by oversuppressing immune responses via the secretion of immunosuppressive cytokines, such as transforming growth factor (TGF)-β and interleukin-10. In the present study, we examined the association of Tregs with <italic>Mycoplasma bovis</italic> infection, in which immunosuppression is frequently observed. Compared with uninfected cattle, the percentage of Tregs, CD4<sup>+</sup>CD25<sup>high</sup>Foxp3<sup>+</sup> T cells, was increased in <italic>M</italic>. <italic>bovis</italic>-infected cattle. Additionally, the plasma of <italic>M</italic>. <italic>bovis</italic>-infected cattle contained the high concentrations of TGF-β1, and <italic>M</italic>. <italic>bovis</italic> infection induced TGF-β1 production from bovine immune cells in <italic>in vitro</italic> cultures. Finally, we analyzed the immunosuppressive effects of TGF-β1 on bovine immune cells. Treatment with TGF-β1 significantly decreased the expression of CD69, an activation marker, in T cells, and Th1 cytokine production <italic>in vitro</italic>. These results suggest that the increase in Tregs and TGF-β1 secretion could be one of the immunosuppressive mechanisms and that lead to increased susceptibility to other infections in terms of exacerbation of disease during <italic>M</italic>. <italic>bovis</italic> infection.</p>