nature publishing group REVIEW Ovarian steroid hormones: effects on immune responses and Chlamydia trachomatis infections of the female genital tract LM Hafner1, K Cunningham1 and KW Beagley1 Female sex hormones are known to regulate the adaptive and innate immune functions of the female reproductive tract. This review aims to update our current knowledge of the effects of the sex hormones estradiol and progesterone in the female reproductive tract on innate immunity, antigen presentation, specific immune responses, antibody secretion, genital tract infections caused by Chlamydia trachomatis, and vaccine-induced immunity. INTRODUCTION depicts the FGT anatomy and the location and relative A critical function of the unique mucosal immune system of the abundances of innate immune cells at this mucosal site.6,8–15 female genital tract (FGT) is to identify and eliminate In the FGT, the major lymphocyte components are natural potentially pathogenic viral and bacterial agents and to provide killer (NK) cells and T lymphocytes, including cluster of protection against sexually transmitted diseases. Globally, it has differentiation (CD) 3 þ T lymphocytes that are present in all been estimated that in adults between 15 and 49 years of age the tissues of the tract. In the LGT, the CD8 þ and CD4 þ are there were 105.7 million cases of new Chlamydia trachomatis dispersed throughout the stroma while lymphoid aggregates of sexually transmitted infections (STIs) in 2008.1 Significant these cells are formed in the uterus.16 Granulocytes are disease sequelae following chlamydial infections of the FGT present and these are principally located in the fallopian include pelvic inflammatory disease, tubal infertility, and tubes. Finally, relative to T lymphocytes, smaller numbers of ectopic pregnancy.2–4 monocytes and B lymphocytes are found throughout all tissues The FGT comprises several immune compartments found in of the FGT.17 the upper genital tract (UGT; endocervix, ovaries, fallopian Immune cells at this site express both surface and cytosolic tubes, and uterus) and lower genital tract (LGT) (ectocervix and pattern recognition receptors (PRRs), including among vagina). The UGT with Type I mucosa5 is lined with a single others Toll-like receptors (TLRs) and the nucleotide-binding layer of columnar epithelium and the LGT with Type II mucosa oligomerization domain (NOD)-like receptors. TLRs 2 and 4 is lined with stratified squamous epithelium (reviewed in are highly expressed in the UGT (fallopian tubes and Pudney et al.6). The transitional zone where squamous cervix) when compared with expression levels in the LGT epithelium changes to columnar epithelium is the most (endometrium and ectocervix) while TLRs 7, 8 and 9 and immunologically active site of the FGT. Although currently NOD-1 (which is involved in sensing Chlamydia infection) and documented (relative) microbial sterility is found in the NOD-2 are expressed at similar levels throughout the tract.18–20 uterus and fallopian tubes, commensal vaginal flora such as In addition to providing a physical barrier for protection, Lactobacillus crispatus are found in the LGT and are under the genital tract epithelial cells (ECs) lining the FGT are hormonal influences at this site.7 immunologically active cells. For example, they act as key The human FGT contains components of the innate and initiators of innate and adaptive immunity by secreting adaptive mucosal immune responses that are found in various cytokines and chemokines, including interleukin (IL)-1b, distributions at different sites throughout the tract. Figure 1 tumor necrosis factor a (TNF-a), IL-6, IL-8, and GM-CSF 1Infectious Diseases Program, Institute of Health and Biomedical Innovation (IHBI), Queensland University of Technology (QUT), Kelvin Grove, Queensland, Australia. Correspondence: LM Hafner ([email protected]) Received 5 June 2011; accepted 4 June 2013; published online 17 July 2013. doi:10.1038/mi.2013.46 MucosalImmunology | VOLUME 6 NUMBER 5 | SEPTEMBER 2013 859 REVIEW Figure 1 The female genital tract: anatomy and innate immune cells of the genital mucosa. This figure depicts non-immune and innate immune cells found throughout the female genital tract, including macrophages, dendritic cells, neutrophils and natural killer (NK) cells. Immune cell receptors are shown on immune cells. Note that epithelial cell receptors CD4, C-C motif chemokine receptor 5 (CCR5), C-X-C motif chemokine receptor 4 (CXCR4) and GalC on endometrial and endocervical cells are not shown in this figure. TLR, Toll-like receptor; NKG2D, an activating receptor expressed on NK cells that binds to MHC class 1 chain–related protein A and B (MICA and MICB). (granulocyte-macrophages colony-stimulating factor), in The recruitment and function of immune components of the response to human chlamydial infections.21 FGT are precisely regulated by hormonal changes during the Host protection of the FGT is afforded by two arms of menstrual cycle by the sex steroids that co-ordinate cell defense comprising innate and acquired immunity. The cellular trafficking and immune activation at this mucosal site. Female components of specific immune responses at this site are T sex hormones estrogens, progestins, and androgens are lymphocytes expressing ab- and gd-T-cell receptors (TCR) and produced by ovarian cells with levels of estradiol (E2 or immunoglobulins (Igs) producing B lymphocytes.22 Effectors 17b-estradiol) and progesterone or P4 (pregn-4-ene3, of non-specific responses include ECs, monocytes, macro- 20-dione) varying in accordance with fluctuations in the phages, granulocytes (neutrophils, eosinophils, and basophils), menstrual cycle.22 In the menstrual/ovarian cycle of humans, dendritic cells (DCs), and NK cells that confer protection due to the endometrium develops and follicles grow until ovulation in chemokines, cytokines, and phagocytosis. Cells of both the the Proliferative/Follicular phase. The Secretory/Luteal phase is innate and adaptive immune systems are found in fallopian characterized by high levels of progesterone from the corpus tubes, uterus, cervix, and vagina.23 Localization of T-lymphocyte luteum to maintain the endometrium. Finally, corpus luteum populations in the female UGT and LGT over the menstrual regression and menstruation occurs during the menstrual cycle is summarized in Table 1.10–15,24–40 phase. At menstruation, serum E2 levels measure typically Innate host defense, particularly in the LGT, is provided by o50 pg ml À 1. Gradually, increasing amounts of E2 are found the vaginal microbiota maintained in a healthy equilibrium in the follicular (proliferative) phase of the adult female (reviewed in Farage et al.41) as well as by the myriad of menstrual cycle with serum levels at a pre-ovulatory stage antimicrobial peptides and protease inhibitors of cervicovaginal (day 14) ranging from 110–410 pg ml À 1 and dropping briefly fluid (Cole42 and reviewed in Farage et al.41 and Wira et al.43). at ovulation. Levels of E2 (20–160 pg mol À 1) and P4 The antimicrobial peptides and PRR TLRs are key inter- (45ngmlÀ 1) are present during the luteal (secretory) phase mediaries of innate immunity in the FGT.43–46 from days 14–28 of the menstrual cycle typically peaking at day 860 VOLUME 6 NUMBER 5 | SEPTEMBER 2013 | www.nature.com/mi Mucosal Table 1 Localization of T lymphocytes in the female upper (UGT) and lower (LGT) genital tracts: effects of menstrual cycle stage and chlamydial infection Immunology Menstrual cycle stage Upper genital tract (UGT) Lower genital tract (LGT) (ovarian phase) Fallopian Proliferative Secretory Chlamydia trachomatis T lymphocytes Ovaries tubes Uterus/endometrium Endocervix Ectocervix Vagina (follicular) (luteal) genital tract infection References | VOLUME 6 NUMBER 5 1 1 Serum estradiol 220 pmol l À o130 pmol l À 1 1 Progesterone o2ngmlÀ 45ngmlÀ T helper cells CD45 þ ,CD3þ , CD45 þ cells CCR5 þ CD4 þ CD3 þ , CD3 þ CD4 þ (30–40% CCR5 þ ( þ ) CCR5 þ ( þ ) Endocervix: CD4 þ cells Kaldensjo¨ 24 CD4 þ Th1, Th2, CD3 þ CD8 þ CD3 þ CD45 þ CD4 þ CD4 þ of vaginal T cells) CD45 þ leu- CD45 þ leu- ( þþþþ) Hamad25 | SEPTEMBER 2013 Th3, Th17 or TFH 4% than CD3 þ kocytes ( þ ) kocytes ( þ ) Endometrium CCR5 and Shaw et al.26 CD3 þ CD4 þ (mid-luteal) (mid-luteal) CD103 cells ( þ ) Cervix Dispep et al.27 CD3 þ CD4 þ Ficarra28 Johansson et al.29 Kamat & Isaacson30 Starkey et al.31 Vassiliadou & Bulmer32 Agrawal et al.35 CytotoxicT cells CD45 þ ,CD3þ , þ CD3 þ CTL þþ þm (uterus) k(uterus) White et al.33 CD8 þ CD8 þ CTL CD8 þ CTL activity ( þþþ) 450% kCTL activity CD8 þ cells Cervix White et al.33 activity vaginal T cells (no change in CD3 þ CD8 þ Li et al.34 CD8 þ cell Ficarra28 number) Johansson et al.29 Agrawal et al.35 CD8 þ CTL CTL activity CTL activity Measurable Measurable White et al.36 CD8 þ CD4 À Yeaman et al.16 Treg cells Natural CD4 þ , þ mLevels kLevels Increased expression of Arrivito et al.37 CD25 þ FoxP3 þ correlating significant FoxP3 þ cells primarily Tai et al.38 Adaptive Tr1 and Th3 with E2 after ovulation in UGT Marks et al.39 k (uterus) Levels (E2 at REVIEW mLevels (E2 at physiological physiological doses) doses) 861 REVIEW 21 of the cycle. At the end of the secretory phase, E2 levels return 40 ¨ to their menstrual levels. et al. 24 The sex hormones E2 and P4 are key contributors to susceptibility and innate and acquired immune responses to Kaldensjo et al. Kelly bacterial and viral infections of the FGT47 (reviewed in Bouman et al.,22 Rakasz et al.48 and Butts et al.49). It is also known that þ these hormones contribute to the sex-based differences both in 7 b innate and in acquired immunity and infectious diseases with þ 4 a estrogens affecting levels of chemokine receptors by T cells and the higher CD4 þ T-cell populations in women undergoing significant changes during the ovarian cycle (reviewed in 50 genital tract infection References Chlamydia trachomatis Fish ).