Retrospective studies performed in specific CIDs [Wiskott-Aldrich syndrome (WAS), MHCII expression deficiency, CD40L deficiency, dedicator of cytokinesis 8 (DOCK8) deficiency] (40–42) advocate for early transplantation before organ damage development or occurrence of severe, chronic infections [see reviews on Hematopoietic stem cell transplantation for WAS and DOCK8 deficiency (26) and for MHC class II expression deficiency]. The gene discussed is CD40LG; the disease is Wiskott-Aldrich syndrome.