Lymphotoxin-alpha (LT alpha) and Lymphotoxin-beta (LT beta) are members of the TNF superfamily designated TNFSF1 and TNFSF3, respectively. LT alpha is a soluble protein while LT beta is a type II transmembrane protein. Secreted LT alpha will assemble as a homotrimer, LT alpha 3, or as a complex with membrane-associated LT beta to generate two types of heterotrimers, LT alpha 1/beta 2 and LT alpha 2/beta 1. Lymphotoxins are expressed by activated CD4+ T cells, unpolarized IL-2-secreting effector T cells, and Th1 effector cells.