CD19 and Huntington disease: A Fab-PLA study showed an increased BCR-IgM:CD19, Igα:pSyk, Igα:pYp110δ, and Igα:pAkt proximity in RTX-treated compared to untreated HD B cells, indicating that the RTX treatment is accompanied by increases of BCR-associated Syk/PI-3kinase signaling and B cell activation (SI Appendix, Figs. S3 and S4).