TNF Receptor Type I, is also known as TNF R-p55/p60 and TNFRSF1A. It is a type I transmembrane protein member of the TNF receptor superfamily. It is expressed in most cell types. Binding of either TNF-α or TNF-β to TNF-R1 initiates a signal transduction pathway that results in the activation of the transcription factor NF-κB, whose target genes are involved in the regulation of inflammatory responses, and, in certain cells, induce apoptosis. TNF-R1 is essential for proper development of lymph node germinal centers and Peyer’s patches and for combating intracellular pathogens such as Listeria. It is stored in the Golgi and translocates to the cell surface following proinflammatory stimuli.

> 95% as determined by SDS-PAGE