CD40LG and X-linked hyper-IgM syndrome: 19 Allen Allen RC RC Armitage Armitage RJ RJ Conley Conley ME ME Rosenblatt Rosenblatt H H Jenkins Jenkins NA NA Copeland Copeland NG NG CD40 ligand gene defects responsible for X-linked hyper-IgM syndrome CD40 ligand gene defects responsible for X-linked hyper-IgM syndrome Science.