TNF-α is released from macrophages, monocytes, neutrophils, T-cells (principally CD4+), NK-cells and many transformed cell lines. Soluble homotrimeric TNF-α is released from cells by proteolysis of the integral membrane precursor form of TNF-α. TNF-α binding to some TNF-α receptors induces apoptosis and depending on cell type, receptor expression, and signal transduction status can induce other responses. TNF-α is involved in the inflammatory response.