Tumour necrosis factor-alpha, molecular model - stock illustration

Tumour necrosis factor-alpha (TNF-alpha), molecular model. This protein generally exists as a trimer (a molecule consisting of 3 identical smaller molecules). It is released by white blood cells, mostly macrophages, during inflammatory immune responses, and acts as a signalling molecule. Its release is triggered by injury or bacterial endotoxins. One of its actions is to kill tumour cells, hence its name. TNF-alpha is also involved in a number of inflammatory diseases, including rheumatoid arthritis, psoriasis and Crohn's disease.