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Proc Natl Acad Sci U S A. 2017 Aug 15;114(33):E6892-E6901. doi: 10.1073/pnas.1621253114. Epub 2017 Aug 1.

IL-4-secreting eosinophils promote endometrial stromal cell proliferation and prevent Chlamydia-induced upper genital tract damage.

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Department of Comparative Medicine, Stanford University School of Medicine, Stanford, CA 94305;
Department of Comparative Medicine, Stanford University School of Medicine, Stanford, CA 94305.
National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709.
Department of Pathobiology, Ontario Veterinary College, University of Guelph, Guelph, ON, Canada, N1G 2W1.
Department of Surgery, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213.
College of Medicine and Life Sciences, University of Toledo, Toledo, OH 43614.
Department of Microbial Infection and Immunity, Centre for Microbial Interface Biology, College of Medicine, The Ohio State University, Columbus, OH 43210.


Genital Chlamydia trachomatis infections in women typically are asymptomatic and do not cause permanent upper genital tract (UGT) damage. Consistent with this presentation, type 2 innate and TH2 adaptive immune responses associated with dampened inflammation and tissue repair are elicited in the UGT of Chlamydia-infected women. Primary C. trachomatis infection of mice also causes no genital pathology, but unlike women, does not generate Chlamydia-specific TH2 immunity. Herein, we explored the significance of type 2 innate immunity for restricting UGT tissue damage in Chlamydia-infected mice, and in initial studies intravaginally infected wild-type, IL-10-/-, IL-4-/-, and IL-4Rα-/- mice with low-dose C. trachomatis inoculums. Whereas Chlamydia was comparably cleared in all groups, IL-4-/- and IL-4Rα-/- mice displayed endometrial damage not seen in wild-type or IL-10-/- mice. Congruent with the aberrant tissue repair in mice with deficient IL-4 signaling, we found that IL-4Rα and STAT6 signaling mediated IL-4-induced endometrial stromal cell (ESC) proliferation ex vivo, and that genital administration of an IL-4-expressing adenoviral vector greatly increased in vivo ESC proliferation. Studies with IL-4-IRES-eGFP (4get) reporter mice showed eosinophils were the main IL-4-producing endometrial leukocyte (constitutively and during Chlamydia infection), whereas studies with eosinophil-deficient mice identified this innate immune cell as essential for endometrial repair during Chlamydia infection. Together, our studies reveal IL-4-producing eosinophils stimulate ESC proliferation and prevent Chlamydia-induced endometrial damage. Based on these results, it seems possible that the robust type 2 immunity elicited by Chlamydia infection of human genital tissue may analogously promote repair processes that reduce phenotypic disease expression.


Chlamydia trachomatis; endometrial stromal cells; endometrium; eosinophils; interleukin 4

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