CD27 and atrial fibrillation: Our MR analysis has identified 8 immune cell phenotypes with a causal relationship to AF, including IgD- CD38dim AC, CD4 + CD8dim AC, BAFF-R on IgD + CD38- naive, CD25 on IgD + CD38dim, CD27 on IgD- CD38br, CX3CR1 on CD14 + CD16- monocyte, CD64 on monocyte, and SSC-A on myeloid DC.