TNFRSF1B, also known as TNFR2 or CD120b or p75, is a member of the tumor necrosis factor receptor superfamily, which also contains TNFRSF1A. Tumor necrosis factor (TNF, TNFSF2) is a multifunctional cytokine that plays a key role in regulating inflammation, immune functions, host defense, and apoptosis. TNF signals through TNFRSF1A and TNFRSF1B. TNFRSF1A is widely expressed, whereas TNFRSF1B exhibits more restricted expression, being found on CD4 and CD8 T lymphocytes, endothelial cells, microglia, oligodendrocytes, neuron subtypes, cardiac myocytes, thymocytes and human mesenchymal stem cells. Both TNFRSF1A and TNFRSF1B can also exist in soluble forms, probably derived by proteolytic cleavage from the cell surface forms. Various defects in the TNFRSF1B pathway, due to polymorphisms in the TNFRSF1B gene, upregulated expression of TNFRSF1B and TNFRSF1B shedding, have been implicated in the pathology of several autoimmune disorders.