design: Peripheral blood samples were collected from a APOBEC2-deficient patient and the patients healthy mother. The blood samples were processed to isolate CD3+ (T cells) and CD19+ (B cells) using a FACS Aria into Eppendorf tubes containing 2% FBS in PBS. After centrifugation at 350 RCF for 10 minutes, total RNA was extracted from the sorted cells using the RNeasy Mini Kit (Qiagen) following the manufacturers protocol. RNA from both the patient and the healthy mother was sent to DKFZ for ultra-low input library preparation and sequencing using NovaSeq 6K PE 50 SP.