Complement protein concentrations and activity in human cervical mucus

Area of Science:

• Immunology
• Reproductive Biology
• Mucosal Immunology

Background:

• The complement system is crucial for mucosal immunity, but its role in the female reproductive tract (FRT) is poorly understood.
• Hormonal fluctuations during the menstrual cycle may impact complement-mediated protection in the vaginal mucosa.

Purpose of the Study:

• To systematically quantify complement component levels in cervical mucus (CM) and serum (S) across the menstrual cycle.
• To characterize the dynamics of complement in the FRT and its potential hormonal regulation.

Main Methods:

• Ten healthy women provided paired CM and serum samples during follicular, ovulatory, and luteal phases.
• Bead-based multiplex assays were used to quantify 13 primary complement components.

Main Results:

• All 13 complement proteins were detected in CM and S, with C3b/iC3b predominant in CM and C4 in S.
• Complement concentrations were significantly lower in CM than in S, except for C3b/iC3b and C2.
• Levels of C2, C4b, and C5a in CM varied significantly across menstrual cycle phases, while serum levels remained constant.

Conclusions:

• Cervical mucus contains detectable and functional complement proteins.
• Normative values for complement components in CM across the menstrual cycle were established.
• This study provides a foundation for understanding FRT immune mechanisms and hormonal influences on mucosal immunity.