The CD40 antigen is a single chain glycoprotein that is known to be a member of the tumor necrosis factor/nerve growth factor superfamily and shows a significant homology to the Hodgkin's disease associated antigen, CD30. CD40 is present on all B cells except plasma cells and is also found on some epithelial cells, carcinomas and lymphoid dendritic cells. CD40 has been found to be essential in mediating a broad variety of immune and inflammatory responses including T cell-dependent immunoglobulin class switching, memory B cell development, and germinal center formation. AT-hook transcription factor AKNA is reported to coordinately regulate the expression of CD40, which may be important for homotypic cell interactions. Adaptor protein TNFR2 interacts with CD40 and serves as a mediator of the signal transduction. The interaction of CD40 and its ligand is found to be necessary for amyloid-beta-induced microglial activation, and thus is thought to be an early event in Alzheimer disease pathogenesis. Two alternatively spliced transcript variants of CD40 encoding distinct isoforms have been reported. Diseases associated with CD40 dysfunction include Type 3 Hyper-Igm immunodeficiency and CD40 ligand deficiency.
B-cell surface antigen CD40; Bp50; CD antigen CD40; CD40; CD40L receptor; Immunoglobulin M; ImmunoglobulinM; MGC9013; sCD40; soluble CD40; T-cell differentiation antigen; Tumor necrosis factor receptor superfamily member 5; tumor necrosis factor receptor superfamily, member 5