title: Identification and partial characterization of a novel plasma membrane-associated lytic factor isolated from highly purified adherent lymphokine-activated killer cells.
abstract: We have identified and partially purified a novel cytolytic factor isolated from enriched plasma membranes prepared from highly purified lymphokine-activated killer cells (adherent-LAK. A-LAK cells) and a large granular lymphocytic NK cell leukemia, CRNK-16. The enriched plasma membranes were shown to be physically devoid of lytic granules and contained no detectable pore-forming protein (PFP, perforin) activity. The plasma membrane-associated cytolytic factor (designated M-CTX) was solubilized in biologically active form and was highly lytic to a large panel of target cells in 2- to 4-hr 51Cr release assays. Characteristics of the M-CTX include: (1) it is plasma membrane- not granule-associated: (2) it is not hemolytic and functions in the absence of Ca2+: (3) nucleated target cells are lysed in 2 to 4 hr at 37 degrees C but not at 4 degrees C: (4) it induces apoptotic cell death with nuclear DNA fragmentation and massive membrane blebbing: (5) it is isolated from the plasma membranes of cultured A-LAK cells, a lytically active LGL leukemia (CRNK-16), and fresh spleen cells but not from thymocytes or L929 fibroblasts: and (6) the lytic activity of the partially purified toxin is inactivated by trypsin, serum, and heat, but is not blocked by antibodies that inactivate TNF-alpha, LT or IFN-gamma. Taken collectively, these data suggest that M-CTX may represent a heretofore undescribed membrane-associated toxin possibly involved in contact-mediated cell killing.
authors.affiliation: Department of Pathology and Pittsburgh Cancer Institute, University of Pittsburgh, Pennsylvania 15213.
authors.forename: R E
authors.initials: RE
authors.lastname: Felgar
authors.forename: J C
authors.initials: JC
authors.lastname: Hiserodt
mesh_terms: D000818:Animals; D002462:Cell Membrane / Q000737:chemistry*; D003601:Cytotoxicity Tests, Immunologic; D003603:Cytotoxins / Q000737:chemistry / Q000302:isolation & purification*; D015979:Killer Cells, Lymphokine-Activated / Q000737:chemistry*; D007694:Killer Cells, Natural / Q000737:chemistry*; D008565:Membrane Proteins / Q000302:isolation & purification*; D051379:Mice; D051381:Rats; D011916:Rats, Inbred F344; D014407:Tumor Cells, Cultured
chemical_list: D003603:Cytotoxins; D008565:Membrane Proteins