Tumor necrosis factors (or the TNF family) refer to a group of cytokines that can cause cell death (apoptosis). The first two members of the family to be identified were:

• Tumor necrosis factor (TNF), formerly known as TNFa or TNF alpha, is the best-known member of this class. TNF is a monocyte-derived cytotoxin that has been implicated in tumor regression, septic shock, and cachexia. The protein is synthesized as a prohormone with an unusually long and atypical signal sequence, which is absent from the mature secreted cytokine. A short hydrophobic stretch of amino acids serves to anchor the prohormone in lipid bilayers. Both the mature protein and a partially processed form of the hormone can be secreted after cleavage of the propeptide.
• Lymphotoxin-alpha, formerly known as Tumor necrosis factor-beta (TNF-ß), is a cytokine that is inhibited by interleukin 10.