Innate Lymphoid Cells Are Required for Endometrial Resistance to Chlamydia trachomatis Infection

Abstract

In some women, sexually transmitted Chlamydia trachomatis may ascend to infect the endometrium, leading to pelvic inflammatory disease. To identify endometrial innate immune components that interact with Chlamydia, we introduced C. trachomatis into mouse endometrium via transcervical inoculation and compared the infectious yields in mice with and without immunodeficiency. Live C. trachomatis recovered from vaginal swabs or endometrial tissues peaked on day 3 and then declined in all mice with or without deficiency in adaptive immunity, indicating a critical role for innate immunity in endometrial control of C. trachomatis infection. Additional knockout of interleukin 2 receptor common gamma chain (IL-2Rγc) from adaptive immunity-deficient mice significantly compromised the endometrial innate immunity, demonstrating an important role for innate lymphoid cells (ILCs). Consistently, deficiency in IL-7 receptor alone, a common gamma chain-containing receptor required for ILC development, significantly reduced endometrial innate immunity. Furthermore, mice deficient in RORγt or T-bet became more susceptible to endometrial infection with C. trachomatis, suggesting a role for group 3-like ILCs in endometrial innate immunity. Furthermore, genetic deletion of gamma interferon (IFN-γ) but not IL-22 or antibody-mediated depletion of IFN-γ from adaptive immunity-deficient mice significantly compromised the endometrial innate immunity. Finally, depletion of NK1.1⁺ cells from adaptive immunity-deficient mice both significantly reduced IFN-γ and increased C. trachomatis burden in the endometrial tissue, confirming that mouse ILCs contribute significantly to endometrial innate immunity via an IFN-γ-dependent effector mechanism. It will be worth investigating whether IFN-γ-producing ILCs also improve endometrial resistance to sexually transmitted C. trachomatis infection in women.

Keywords: Chlamydia trachomatis; endometrial resistance; innate immunity; innate lymphoid cells.

FIG 1

Comparison of live C. trachomatis yields in vaginal swabs between mice with and without adaptive immunity following transcervical inoculation. C57BL/6J mice without (solid bars) or with (open bars) deficiency in adaptive immunity or Rag1 (Rag1^−/−) were infected with 5 × 10⁶ IFU of C. trachomatis serovar D organisms via transcervical inoculation and were then monitored for live-organism recovery from the genital tract by taking vaginal swabs on days 1, 3, 5, 7, 10, and 14 and weekly thereafter. The number of live organisms recovered from each swab at each time point was expressed as log₁₀ IFU, and group means and standard deviations are shown. n = 4 for each data point from two independent experiments. P values were >0.05 (Wilcoxon rank sum) between the two groups of mice when IFU from the first 7 days were compared and <0.05 between the two groups when IFU from days 10 to 56 or days 1 to 56 were compared.

FIG 2

Comparison of live C. trachomatis yields in genital tract tissues between mice with or without adaptive immunity following transcervical inoculation. C57BL/6J mice without (solid bars; n = 7) or with (open bars; Rag1^−/−; n = 6) deficiency in adaptive immunity were infected with 5 × 10⁶ IFU of C. trachomatis serovar D organisms via transcervical inoculation. All mice were monitored for live-organism recovery from the genital tract tissues, including vagina (Vag), cervix (Cex), uterus or uterine horn (UH), and oviduct or ovary (OV). The tissues were harvested on day 3 after transcervical inoculation. The number of live organisms recovered from each tissue is expressed as log₁₀ IFU, and group means and standard deviations are shown. Data are from two independent experiments. P was >0.05 (Wilcoxon rank sum test) between C57BL/6J and Rag1^−/− mice when IFU from any given tissue were compared.

FIG 3

Comparison of live C. trachomatis yields between adaptive immunity-deficient mice with or without IL-2Rγc following transcervical inoculation. Mice deficient in Rag1 (Rag1^−/−; solid bars) or in both Rag2 and IL-2Rγc (Rag2^−/− & γc^−/−; open bars) were infected with 5 × 10⁶ IFU of C. trachomatis serovar D organisms via transcervical inoculation and then monitored for live-organism recovery from both vaginal swabs and genital tract tissues, including vagina (Vag), cervix (Cex), uterus or uterine horn (UH), and oviduct or ovary (OV). All swabs and tissues were harvested on day 3 after inoculation. The number of live organisms recovered from each swab or tissue is expressed as log₁₀ IFU, and group means and standard deviations are shown. n = 5 for each data point, and the data are from two independent experiments. *, P < 0.05 (Wilcoxon rank sum test).

FIG 4

Comparison of live C. trachomatis yields between mice with or without deficiency in IL-7 receptor following transcervical inoculation. Mice without (solid bars) or with (IL-7R^−/−; open bars) IL-7 receptor deficiency were infected with 5 × 10⁶ IFU of C. trachomatis serovar D organisms via transcervical inoculation and then monitored for live-organism recovery from both swabs and genital tract tissues, including vagina (Vag), cervix (Cex), uterus or uterine horn (UH), and oviduct or ovary (OV). All swabs and tissues were harvested on day 3 after inoculation. The number of live organisms recovered from each swab or tissue is expressed as log₁₀ IFU, and group means and standard deviations are shown. n = 4 for each data point and the data were from two independent experiments. *, P < 0.05 (Wilcoxon rank sum test).

FIG 5

Comparison of live C. trachomatis yields between mice with or without deficiency in T-bet or RORγt following transcervical inoculation. Mice without (solid bars) or with deficiency in transcriptional factors T-bet (T-bet^−/−; open bars) or RORγt (RORγt^−/−; hatched bars) were infected with 5 × 10⁶ IFU of C. trachomatis serovar D organisms via transcervical inoculation and then monitored for live-organism recovery from both swabs and genital tract tissues, including vagina (Vag), cervix (Cex), uterine/uterine horn (UH), and oviduct/ovary (OV). All swabs and tissues were harvested on day 3 after inoculation. The number of live organisms recovered from each swab or tissue was expressed as log₁₀ IFU, and group means and standard deviations are shown. n = 5 for each data point, and the data are from two independent experiments. *, P < 0.05, and **, P < 0.01, for comparison of the indicated gene-deficient group with the wild-type group (Wilcoxon rank sum test).

FIG 6

Comparison of live C. trachomatis yields between mice with or without deficiency in IFN-γ or IL-22 following transcervical inoculation. Mice without (solid bars; n = 10) or with (open bars; IFN-γ^−/−; n = 4) or IL-22 (hatched bars; IL-22^−/−; n = 7) deficiency in IFN-γ were infected with 5 × 10⁶ IFU of C. trachomatis serovar D organisms via transcervical inoculation and then monitored for live-organism recovery from both swabs and genital tract tissues, including vagina (Vag), cervix (Cex), uterus or uterine horn (UH), and oviduct/ovary (OV). All swabs and tissues were harvested on day 3 after inoculation. The number of live organisms recovered from each swab or tissue is expressed as log₁₀ IFU, and group means and standard deviations are shown. Data are from two independent experiments. *, P < 0.05 (Wilcoxon rank sum test).

FIG 7

Comparison of live C. trachomatis yields between adaptive immunity-deficient mice with or without depletion of IFN-γ following transcervical inoculation. Adaptive immunity-deficient mice without (Rag1^−/− + Ctrl IgG; solid bars) or with (Rag1^−/− + αIFN-γ; open bars) depletion of IFN-γ were infected with 5 × 10⁶ IFU of C. trachomatis serovar D organisms via transcervical inoculation and then monitored for live-organism recovery from both swabs and genital tract tissues, including vagina (Vag), cervix (Cex), uterus or uterine horn (UH), and oviduct or ovary (OV). All swabs and tissues were harvested on day 3 after inoculation. The number of live organisms recovered from each swab or tissue is expressed as log₁₀ IFU, and group means and standard deviations are shown. n = 4 for each data point, and data are from two independent experiments. *, P < 0.05 (Wilcoxon rank sum test).

FIG 8

Comparison of live C. trachomatis yields between adaptive immunity-deficient mice with or without depletion of NK1.1⁺ cells following transcervical inoculation. Adaptive immunity-deficient mice without (Rag1^−/− + Ctrl IgG; solid bars) or with (Rag1^−/− + αNK1.1; open bars) depletion of NK1.1⁺ cells were infected with 5 × 10⁶ IFU of C. trachomatis serovar D organisms via transcervical inoculation. The infected mice were then monitored for live-organism recovery (a) and IFN-γ production (b) from genital tract tissues, including vagina (Vag), cervix (Cex), uterus or uterine horn (UH), and oviduct or ovary (OV). All tissues were harvested on day 7 after inoculation. Group means and standard deviations for numbers of live organisms recovered from each tissue (expressed as log₁₀ IFU) and IFN-γ measured from the same tissues are shown. n = 4 to 5 for each data point from two independent experiments. *, P < 0.05 (Wilcoxon rank sum test).