It is a protein that is produced by Th1 type T-cells and induces vascular endothelial cells to change their surface adhesion molecules to allow phagocytic cells to bind to them. It is also known to be required for normal development of Peyer's patches. 
Lymphotoxin is homologous to Tumor Necrosis Factor beta, but secreted by T-cells. It is paracrine due to the small amounts produced. The effects are similar to TNF-alpha, but TNF-beta is also important for the development of lymphoid organs.
^Parham, Peter (2005). "Chapter 6: T-cell mediated immunity". The immune system (2nd ed.). New York: Garland Science. p. 172. ISBN0-8153-4093-1.
^Kumar. "Chapter 13 – Diseases of White Blood Cells, Lymph Nodes, Spleen, and Thymus". In Kumar. Robbins and Cotran Pathologic Basis of Disease, Professional Edition (8th ed. ed.).|accessdate= requires |url= (help)