Fig. 2
From: Gene therapy for ultrarare diseases: a geneticist’s perspective

Mechanisms of lentiviral vector-modified autologous CD34+ hematopoietic stem cell transplantation. Transduction of hematopoietic stem cells can correct functional defects in blood cells, including T cells, B cells, and macrophages. Transgenes can encode secretory proteins that are secreted into the systemic circulation. The secreted protein, if it contains a brain-targeting epitope, can enter the brain. Bone marrow-derived cells can also migrate to the brain and differentiate into microglia, which can ameliorate brain defects