CD40 ligand (CD40-L) (Tumor necrosis factor ligand superfamily member 5) (CD154 antigen) [Contains- CD40 ligand, membrane form; CD40 ligand, soluble form]; Cytokine that binds to TNFRSF5. Mediates B-cell proliferation in the absence of co-stimulus as well as IgE production in the presence of IL-4. Involved in immunoglobulin class switching (By similarity) (260 aa)