Purpose of the Studies. Hyper-IgM immunodeficiency is characterized by recurrent bacterial infections, normal or elevated IgM, and markedly decreased IgG, IgA, and IgE. Previous research suggested that the T cells of these patients are defective in their ability to help B cells make functional antibody. CD40 ligand (CD4OL) is a membrane glycoprotein on activated T helper cells and binds the CD40 molecule expressed on B cells, and induces proliferation and immunoglobulin class switching (in conjunction with IL-4). The gene for the CD4OL has been mapped to position q26.3-q27.1 on chromosome X (same as the Hyper-IgM gene and the area of isotype switching). Several research groups sought to determine if the immunodeficiency in Hyper-IgM patients is due to defective CD4OL.
Findings. The five papers listed above document the work of different research groups that simultaneously found abnormalities in the CD4OL gene in a total of 16 patients with X-linked Hyper-IgM syndrome. Different mutations of the CD4OL gene have been discovered, including point mutations, deletions, and nonsense sequences. Mutant version of CD4OL taken from Hyper IgM patients were unable to "help" B cells in vitro. Thus, deficient CD40/CD40L interactions between B and T cells results in severely impaired immunity. Restricted CD40L gene expression to T cells may ultimately allow gene therapy as treatment.
Reviewers' Comments. A concise editorial by Jean Marx entitled "Cell Communication Failure Leads to Immune Disorder" describes this landmark research and accompanies the Spriggs article in the February 12th issue of Science (pp. 896-897). This discovery may not only lead to treatment of this disorder, but also modification of other less favorable immune responses.
Bell’s palsy in a pediatric patient with hyper IgM syndrome and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)
