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Infect. Immun., Feb 1996, 441-447, Vol 64, No. 2
JA D'Orazio, BC Cole and J Stein-Streilein
While the effects of superantigens on T lymphocytes are well characterized,
how superantigens interact with other immune cells is less clear. This
report examines the effects of Mycoplasma arthritidis mitogen (MAM) on
human natural killer (NK) cell activity. Incubation of peripheral blood
mononuclear cells (PBMC) with MAM for 16 to 20 h augmented NK cytotoxicity
(against K562) in a dose-dependent manner (P < or = 0.05).
Superantigen-dependent cellular cytotoxicity, an activity of
superantigen-activated cytotoxic T cells, was not involved in lysis of K562
cells because the erythroleukemic tumor target cells expressed no class II
major histocompatibility complex by fluorescence-activated cell sorter
analysis. Kinetic experiments showed that the largest increase in NK
activity induced by MAM occurred within 48 h. Incubation with MAM caused a
portion of NK cells to become adherent to tissue culture flasks, a quality
associated with activation, and augmented NK activity was found in both
adherent and nonadherent subpopulations. Experiments using
cytokine-specific neutralizing antibodies showed that interleukin-2
contributed to enhancement of the NK activity observed in
superantigen-stimulated PBMC. Interestingly, MAM was able to augment NK
lysis of highly purified NK (CD56+) cells in the absence of other immune
cells in 9 of 12 blood specimens, with the augmented lytic activity ranging
from 110 to 170% of unstimulated NK activity. In summary, data presented in
this report show for the first time that MAM affects human NK cells
directly by increasing their lytic capacity and indirectly in PBMC as a
consequence of cytokines produced by T cells. Results of this work suggest
that, in vivo, one consequence of interaction with superantigen-secreting
microorganisms may be up- regulation of NK lytic activity. These findings
may have clinical application as a means of generating augmented NK
effector cells useful in the immunotherapy of parasitic infections or
neoplasms.
Copyright © 1996, American Society for Microbiology
Mycoplasma arthritidis mitogen up-regulates human NK cell activity
Department of Microbiology and Immunology, University of Miami School of Medicine 33101, USA.
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