4-1BBL is a transmembrane cytokine that is part of the tumor necrosis factor (TNF) ligand family. Recombinant human 4-1BBL is intended for use in cell culture applications. 4-1BBL and its interaction with 4-1BB is involved in the antigen presenting process, proliferation of CD4 and CD8 positive T-cells, as well as cytokine secretion from T-cells.