The study identifies four immune cell traits as causally contributing to prostate cancer risk, including CD127- CD8+ T cell %CD8+ T cell (OR = 1.0042, 95%CI:1.0011–1.0073, p = 0.0077), CD45RA on CD39+ resting CD4 regulatory T cell (OR = 1.0029, 95%CI:1.0008–1.0050, p = 0.0065), CD62L− Dendritic Cell Absolute Count (OR = 1.0016; 95%CI:1.0005–1.0026; p = 0.0039), CX3CR1 on CD14+ CD16− monocyte (OR = 1.0024, 95%CI:1.0007–1.0040, p = 0.0060). This evidence concerns the gene CD8A and prostate cancer.