CD40 Ligand

CD40L is a member of the tumor necrosis factor (TNF) family expressed on activated T cells after T cell antigen receptor ligation. It binds to the CD40 receptor on В cells and dendritic cells and thereby provides a critical helper T cell' signal necessary for germinal center formation, isotype class switching, and production of, for example. IgG and IgE antibodies. CD40L may also transmit a signal back to T cells, to promote short-term T cell proliferation. CD40L and CD40 are not simply restricted to cells regulating immune responses. The CD40L-CD40 signaling pathway may also play an important role in the regulation of epithelial cell, fibroblast, and smooth muscle cell proliferation.