CD19 and breast cancer: Conversely, certain B-cell subtypes exhibited protective effects, such as CD20 on IgD− CD24− B cells (OR = 0.916, 95% CI = 0.860–0.975; P = .005) and CD19 on transitional B cells (OR = 0.909, 95% CI = 0.852–0.970; P = .004), both of which were associated with a reduced BC risk.