Perforin also known as PRF1 is a protein with structural similarities to complement component C9 that is important in immunity. Perforin plays a crucial role in the immune response, particularly in the cytotoxic activity of T lymphocytes and natural killer cells, which are essential for eliminating virus-infected and tumorigenic cells. Perforin is primarily located in the granules of cytotoxic T lymphocytes and natural killer cells, where Perforin is stored until needed for immune defense. Upon activation, Perforin is exocytosed and forms pores in the target cell membrane, allowing the entry of granzymes, which are serine proteases that induce apoptosis in the target cells. Perforin′s ability to create transmembrane channels is vital for the immune system′s ability to control infections and tumors effectively.