Causal relationship between immune cells and aortic aneurysms: a Mendelian randomization study.

Objectives: The causal association between immune cell traits and aortic aneurysm remains unknown.

Methods: We performed a bidirectional two-sample Mendelian randomization analysis to explore the causality between 731 immune cell characteristics and the risk of abdominal aortic aneurysm and thoracic aortic aneurysms through publicly available genetic data, respectively. To examine heterogeneity and horizontal pleiotropy, Cochran's Q test and MR-Egger intercept were utilized. Additionally, multivariable Mendelian randomization analysis and meta-analysis were performed in further analysis.

Results: We found that 20 immune phenotypes had a suggestive causality on abdominal aortic aneurysm, and 15 immune phenotypes had a suggestive causal effect on thoracic aortic aneurysm. After further false discovery rate adjustment (q value <0.1), CD20 on IgD+ CD38- B cell (q = 0.053) and CD127 on CD28+ CD4+ T cell (q = 0.096) were associated with an increased risk of abdominal aortic aneurysm, respectively, indicating a significant causality between them. After adjusting for smoking, there is still statistical significance between CD127 on CD28+ CD4+ T cell and abdominal aortic aneurysm. However, after adjusting for lipids, no statistical significance can be observed between CD127 on CD28+ CD4+ T cells and abdominal aortic aneurysm. Furthermore, there is still statistical significance between CD20 on IgD+ CD38- B cells and abdominal aortic aneurysm after adjusting for lipids and smoking, which was further identified by meta-analysis.

Conclusions: We found a causal association between immune cell traits and aortic aneurysm by genetic methods, thus providing new avenues for future mechanism studies.