Immunoglobulin class-switching is regulated by NF-κB through various mechanisms [103], e.g., expression of the gene AICD (activation-induced cytidine deaminase) [97, 104], which may account for the decreased switched memory B cells and hypogammaglobulinemia (IgM, IgA, and/or IgG) in NF-κB haploinsufficiency. Here, CD40LG is linked to agammaglobulinemia.