title: Effect of Fas+ and Fas- target cells on the ability of NK cells to repeatedly fragment DNA and trigger lysis via the Fas lytic pathway.
abstract: We and others have recently shown that human NK cells express the Fas ligand (FasL) constitutively and that they can trigger the lysis of Fas positive (Fas+) target cells (TC) by apoptosis. We have also previously demonstrated that NK cells exposed to sensitive TC temporarily lose their ability to lyse sensitive TC via the granule-mediated pathway and that this loss is recovered when inactivated NK cells (NKi) are incubated in medium supplemented with IL-2, IL-12 or IL-15. In this study, we investigated the fate of the Fas-lytic pathway in NK cells exposed to either Fas+ or Fas- TC. To this end, we exposed NK cells to Jurkat (Fas-) or Jurkat (Fas+) TC for up to 6 h, separated NK cells from the TC and assessed the residual lytic activity against K562, a traditional human NK cell target, Jurkat Fas+ and Jurkat Fas- TC. Fas lytic activity was determined in calcium free medium, in the presence or absence of two distinct Fas-blocking monoclonal antibodies and a Fas.Fc fusion protein. In parallel experiments, the extent of DNA fragmentation in the three TCs was also assayed by the JAM test. Our results indicate that: (i) NK cells exposed to susceptible Fas+ TC temporarily lose most of their lytic potential due to the granule-mediated pathway, while only partially losing the Fas-lytic pathway. They also partially lose their ability to fragment DNA. (ii) NK cells exposed to Fas+ TC completely recover the Fas lytic pathway and the ability to fragment DNA via the Fas/Fas ligand when incubated in medium supplemented with IL-2 for 18 h.
authors.affiliation: Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana 46202-5200, USA.
authors.forename: I
authors.initials: I
authors.lastname: Csipo
authors.forename: A H
authors.initials: AH
authors.lastname: Montel
authors.forename: J A
authors.initials: JA
authors.lastname: Hobbs
authors.forename: P A
authors.initials: PA
authors.lastname: Morse
authors.forename: Z
authors.initials: Z
authors.lastname: Brahmi