The vaginal microbiome is a dynamic environment, depending on a complex interplay between microbiota and the host. In physiological conditions, lactobacillus species are the most represented, regulating glycogen metabolism to maintain normal pH. The vagina contains different immune-related cells, represented by several innate and adaptive immune system protective levels and receptors that can recognize and react with the microbial environment. Altered microbiota and the altered interplay between microbiota and the immune system underlie several gynecologic diseases.

The interactions between the host immune system and vaginal microbiota are two-way streets. The host systems are regulated by microbiota, and the host immune system also regulates microbiota. The host-microbiota interaction is necessary for the maintenance of eubiosis, which together support a defense system, with antibacterial substances, cytokines, and defensins, against vaginal dysbiosis, preventing the colonization of anaerobic bacterial species, significantly influencing sexual health and reproductive health, reducing the risk of preterm birth and miscarriage, in addition to sexually transmitted diseases.

This Special Issue aims to bring together original research and review articles discussing important immunological aspects of the interplay of the immune system and vaginal microbiota. We welcome submissions considering the relationship between immune system cells and the vaginal microbiota that govern health or disease status and how this influences outcomes and possible future directions related to women's health. Research can include immunological/molecular studies, cell-based analysis, and human studies.

Potential topics include but are not limited to the following:

• Innate and adaptive immunity in immunological mechanisms of vaginal microbiota
• The role of immunological mechanisms in vaginal microbiome on pregnancy
• Molecular biology of interleukins in vaginal microbiota
• Cellular compartments and pathways involved in the immune mechanisms of vaginal microbiota
• The role of interleukins bacterial/fungal/viral infectious diseases
• The role of cytokines in vaginal microbiota
• Immunological biomarkers of vaginal microbiota
• Immunotherapeutic options for vaginal microbiota
• Microbe and host cell relationship
• Crosstalk among immune cells