Genetic insights into the immunological basis of male infertility: a translational perspective

To elaborate the causal relationships between specific immunocyte phenotypes and male infertility.

Mendelian randomization using genome-wide association study data.

Large cohorts of European ancestry.

731 immunocyte phenotypes or male infertility.

Genetic variants were used as instrumental variables to infer causality, minimizing confounding and bias. The causal associations were assessed using the inverse variance-weighted (IVW) method for primary analysis, and the findings were validated using MR-Egger, Weighted Median, Simple Mode, and Weighted Mode approaches. Additional sensitivity analyses were performed to validate the robustness of the findings.

Our analysis identified significant causal associations between specific immunocyte phenotypes and male infertility. Phenotypes such as naive-mature B cell %lymphocyte (odds ratio [OR] = 1.257) and IgD- CD38dim %B cell (OR = 1.100) were positively associated with increased infertility risk, whereas phenotypes like CD39+ CD8br %T cell (OR = 0.856) and B cells activator of the TNF-α family receptor (BAFF-R) on transitional (OR = 0.833) were negatively associated, suggesting a protective effect. Additionally, reverse MR analysis revealed that male infertility might causally affect certain immunocyte phenotypes, including CD14- CD16+ monocyte %monocyte (OR = 1.049).

This study provides robust evidence for the causal role of specific immunocyte phenotypes in male infertility and highlights the bidirectional relationship between immune function and reproductive health. These findings provide new insights into the immunological factors contributing to male infertility and suggest potential biomarkers and therapeutic targets for future research and clinical interventions.