Ectocervix

Abstract: Toll-like receptor (TLR) signal transduction is a central component of the innate immune response to pathogenic challenge. Although recent studies have begun to elucidate differences in acquired immunity in tissues of the human female reproductive tract, there is a relative paucity of work regarding innate defense mechanisms. We investigated TLR mRNA and protein expression in tissues of the human female reproductive tract. Constitutive mRNA expression of TLRs 1 to 6 was observed in fallopian tubes, uterine endometrium, cervix, and ectocervix. Furthermore, transcripts of the signaling adapter MyD88 and the accessory molecule CD14 were also detected in all tissues assayed. Quantitative analysis of TLR2 mRNA levels revealed highest expression of this molecule in fallopian tube and cervical tissues, followed by endometrium and ectocervix. In contrast to TLR2, TLR4 expression declined progressively along the tract, with highest expression in the upper tissues (fallopian tubes and endometrium), followed by cervix and ectocervix. In addition to mRNA, protein expression of TLR2 and TLR4 was also documented in these tissues. These data suggest that TLRs are differentially expressed in distinct compartments of the female reproductive tract and may provide insight regarding the regulation of inflammation and immunity within the tract.

Abstract: The mucosal epithelium is a major portal for microbial invasion. Mucosal barrier integrity is maintained by the physical interactions of intercellular junctional molecules on opposing epithelial cells. The epithelial mucosa in the female reproductive tract provides the first line of defense against sexually transmitted pathogenic bacteria and viruses, but little is known concerning the structure and molecular composition of epithelial junctions at this site. In the present study, the distribution of tight, adherens, and desmosomal junctions were imaged in the human endocervix (columnar epithelium) and ectocervix (stratified squamous epithelium) by electron microscopy, and permeability was assessed by tracking the penetration of fluorescent immunoglobulin G (IgG). To further define the molecular structure of the intercellular junctions, select junctional molecules were localized in the endocervical, ectocervical, and vaginal epithelium by fluorescent immunohistology. The columnar epithelial cells of the endocervix were joined by tight junctions that excluded apically applied fluorescent IgG. In contrast, the most apical layers of the ectocervical stratified squamous epithelium did not contain classical cell-cell adhesions and were permeable to IgG. The suprabasal and basal epithelial layers in ectocervical and vaginal tissue contained the most robust adhesions; molecules characteristic of exclusionary junctions were detected three to four cellular layers below the luminal surface and extended to the basement membrane. These data indicate that the uppermost epithelial layers of the ectocervix and vagina constitute a unique microenvironment; their lack of tight junctions and permeability to large-molecular-weight immunological mediators suggest that this region is an important battlefront in host defense against microbial pathogens.