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Flow cytometric analysis of the cytotoxic effects of Actinobacillus actinomycetemcomitans leukotoxin on human natural killer cells
Author(s) -
Shenker Bruce J.,
Vitale Laura A.,
Keiba Irene,
Harrison Gerald,
Berthold Peter,
Golub Ellis,
Lally Edward T.
Publication year - 1994
Publication title -
journal of leukocyte biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.819
H-Index - 191
eISSN - 1938-3673
pISSN - 0741-5400
DOI - 10.1002/jlb.55.2.153
Subject(s) - biology , propidium iodide , flow cytometry , viability assay , apoptosis , natural killer cell , cell , cytotoxic t cell , programmed cell death , microbiology and biotechnology , cytolysis , intracellular , immunology , biochemistry , in vitro
Abstract The goal of this investigation was to determine if human natural killer (NK) cells were susceptible to the cytolytic effects of the Actinobacillus actinomycetemcomitans leukotoxin (LTX). Following treatment with LTX (0–200 ng/ml), NK cell activation by interleukin‐2 (IL‐2) was evaluated. LTX inhibited the IL‐2‐induced expression of both CD69 and the IL‐2 receptor. Furthermore, the up‐regulation of CD56 was also impaired. To determine whether the observed functional deficits were the result of cell death, NK cell viability was evaluated by flow cytometry. Changes in forward and side light scatter patterns consistent with cell death were observed within 60 min. Direct analysis of cell viability by measuring propidium iodide exclusion, however, indicated little change in the viability of LTX‐treated NK cells. Electron microscopic analysis of NK cells exposed to LTX revealed early nuclear alterations characterized by hyperchromaticity, nuclear fragmentation, and condensation of nucleoplasm. However, no change in membrane integrity was initially noted. Finally, LTX caused a rapid and sustained elevation in the intracellular levels of Ca 2+ . These morphological and biochemical changes are consistent with the notion of programmed cell death. J. Leukoc. Biol. 55: 153–160; 1994.