Abstract
Adenomyosis-the ectopic presence of endometrial glands and stroma within the myometrium-affects reproductive-age women and is associated with pain, bleeding, and subfertility, yet the immune events that precede pregnancy remain poorly defined. To address this, we investigated how the uterine immune microenvironment evolves before conception in a tamoxifen-induced murine model of adenomyosis. At 1- and 3-months post-induction, we analyzed uterine tissue by immunofluorescence, flow cytometry, and quantitative polymerase chain reaction. We found that adenomyotic uteri exhibited a sustained elevation of interleukin-6 messenger RNA, a transient interleukin-10 rise at 1 month, and stable cyclooxygenase-2 levels. Interleukin-6 receptor messenger RNA and signal transducer and activator of transcription 3 messenger RNA were both transiently downregulated at 1 month and returned to control levels by 3 months. Early in disease development, total macrophage numbers declined and displayed an alternative (M2) activation phenotype, followed by a selective loss of classically activated (M1) macrophages at later stages. B lymphocytes were consistently enriched, indicating enhanced humoral activity. Although overall T-cell counts remained stable, the CD3+ compartment underwent a marked shift from double-negative T lymphocytes toward T-helper and cytotoxic subsets, coinciding with the transient signaling changes. Limitations of our study include reliance on a single animal model, analysis at only two timepoints, and a lack of functional assessment of regulatory T cells. Future work should incorporate finer temporal profiling, single-cell transcriptomics, and validation in human tissues. These findings highlight dynamic innate-adaptive crosstalk as an early driver of adenomyosis pathology and suggest that targeting interleukin-6-mediated pathways may inform biomarker development and novel immunomodulatory interventions.