Cytokine which is involved in epithelial-mesenchymal signaling during morphogenesis of ectodermal organs. Functions as a ligand activating the DEATH-domain containing receptors EDAR and EDA2R. Isoform A1 binds only to the receptor EDAR, while isoform A2 binds exclusively to the receptor EDA2R. May also play a role in cell adhesion. Isoform A1 binds only to the receptor EDAR, while isoform A2 binds exclusively to the receptor EDA2R. Isoform A2 binds exclusively to the receptor EDA2R. Homotrimer. The homotrimers may then dimerize and form higher-order oligomers. Additional isoforms seem to exist. N-glycosylated. Processing by furin produces a secreted form. Belongs to the tumor necrosis factor family.