Archetypal members of the family are complement C9 and perforin, both of which function in human immunity.[4] C9 functions by punching holes in the membranes of Gram-negative bacteria. Perforin is released by cytotoxic T cells and lyses virally infected and transformed cells. In addition, perforin permits delivery of cytotoxic proteases called granzymes that cause cell death.[5] Deficiency of either protein can result in human disease.[6][7] Structural studies reveal that MACPF domains are related to cholesterol-dependent cytolysins (CDCs), a family of pore forming toxins previously thought to only exist in bacteria.[8][9]
^Witzel-Schlömp K, Späth PJ, Hobart MJ, et al. (1997). "The human complement C9 gene: identification of two mutations causing deficiency and revision of the gene structure". J. Immunol. 158 (10): 5043–9. doi:10.4049/jimmunol.158.10.5043. PMID9144525. S2CID22684521.