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Serial killing of tumor cells by human natural killer cells--enhancement by therapeutic antibodies.

Bhat R, Watzl C - PLoS ONE (2007)

Bottom Line: Serial killing is associated with a loss of Perforin and Granzyme B content.IL-2 and IL-15 are equally effective in enhancing the killing frequency of resting NK cells.Therefore, strategies augmenting the killing ability of NK cells can boost the immune system and enhance the effectiveness of monoclonal antibody-based therapies.

View Article: PubMed Central - PubMed

Affiliation: Institute for Immunology, University Heidelberg, Heidelberg, Germany.

ABSTRACT

Background: Natural killer cells are an important component of the innate immune system. Anti-cancer therapies utilizing monoclonal antibodies also rely on the cytotoxicity of NK cells for their effectiveness. Here, we study the dynamics of NK cell cytotoxicity.

Methodology/principal findings: We observe that IL-2 activated human NK cells can serially hit multiple targets. Using functional assays, we demonstrate that on an average, a single IL-2 activated NK cell can kill four target cells. Data using live video microscopy suggest that an individual NK cell can make serial contacts with multiple targets and majority of contacts lead to lysis of target cells. Serial killing is associated with a loss of Perforin and Granzyme B content. A large majority of NK cells survive serial killing, and IL-2 can replenish their granular stock and restore the diminished cytotoxicity of 'exhausted' NK cells. IL-2 and IL-15 are equally effective in enhancing the killing frequency of resting NK cells. Significantly, Rituximab, a therapeutic monoclonal antibody increases the killing frequency of both resting and IL-2 activated NK cells.

Conclusion/significance: Our data suggest that NK cell-based therapies for overcoming tumors rely on their serial killing ability. Therefore, strategies augmenting the killing ability of NK cells can boost the immune system and enhance the effectiveness of monoclonal antibody-based therapies.

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Related in: MedlinePlus

Rituximab increases killing frequency of IL-2 activated NK cells. 221 target cells were treated with Rituximab (10 µg/ml) and killing frequency of NK cells was assessed by 4 h (A) or 16 h (B) 51Cr release assay and compared to untreated or isotype treated targets. (C) Data from three independent donors show that rituximab increases the killing frequency of NK cells two fold as compared to untreated target cells.
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pone-0000326-g006: Rituximab increases killing frequency of IL-2 activated NK cells. 221 target cells were treated with Rituximab (10 µg/ml) and killing frequency of NK cells was assessed by 4 h (A) or 16 h (B) 51Cr release assay and compared to untreated or isotype treated targets. (C) Data from three independent donors show that rituximab increases the killing frequency of NK cells two fold as compared to untreated target cells.

Mentions: Furthermore, we wanted to test if Rituximab could also enhance the killing frequency of IL-2 activated NK cells, which were already highly cytotoxic (Fig. 1). Rituximab treatment resulted in a significant increase of NK cell cytolytic ability and consequently also killing frequency, which was already obvious after 4 hours, but most prominent after 16 hours of incubation with IL-2 activated NK cells (Fig. 6). Data from three independent donors showed an increase of two fold in killing frequency as compared to untreated target cells, reaching a maximum of 6 target cells killed per NK cell after 16 hours (Fig. 6C). Control antibodies showed no effect. We also analyzed the effect of Rituximab treatment on the decrease of Perforin and Granzyme B content using intracellular staining. Data from three donors showed further reduction in Perforin and Granzyme B expression on coincubation with rituximab treated targets as compared to untreated targets (data not shown).


Serial killing of tumor cells by human natural killer cells--enhancement by therapeutic antibodies.

Bhat R, Watzl C - PLoS ONE (2007)

Rituximab increases killing frequency of IL-2 activated NK cells. 221 target cells were treated with Rituximab (10 µg/ml) and killing frequency of NK cells was assessed by 4 h (A) or 16 h (B) 51Cr release assay and compared to untreated or isotype treated targets. (C) Data from three independent donors show that rituximab increases the killing frequency of NK cells two fold as compared to untreated target cells.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC1828617&req=5

pone-0000326-g006: Rituximab increases killing frequency of IL-2 activated NK cells. 221 target cells were treated with Rituximab (10 µg/ml) and killing frequency of NK cells was assessed by 4 h (A) or 16 h (B) 51Cr release assay and compared to untreated or isotype treated targets. (C) Data from three independent donors show that rituximab increases the killing frequency of NK cells two fold as compared to untreated target cells.
Mentions: Furthermore, we wanted to test if Rituximab could also enhance the killing frequency of IL-2 activated NK cells, which were already highly cytotoxic (Fig. 1). Rituximab treatment resulted in a significant increase of NK cell cytolytic ability and consequently also killing frequency, which was already obvious after 4 hours, but most prominent after 16 hours of incubation with IL-2 activated NK cells (Fig. 6). Data from three independent donors showed an increase of two fold in killing frequency as compared to untreated target cells, reaching a maximum of 6 target cells killed per NK cell after 16 hours (Fig. 6C). Control antibodies showed no effect. We also analyzed the effect of Rituximab treatment on the decrease of Perforin and Granzyme B content using intracellular staining. Data from three donors showed further reduction in Perforin and Granzyme B expression on coincubation with rituximab treated targets as compared to untreated targets (data not shown).

Bottom Line: Serial killing is associated with a loss of Perforin and Granzyme B content.IL-2 and IL-15 are equally effective in enhancing the killing frequency of resting NK cells.Therefore, strategies augmenting the killing ability of NK cells can boost the immune system and enhance the effectiveness of monoclonal antibody-based therapies.

View Article: PubMed Central - PubMed

Affiliation: Institute for Immunology, University Heidelberg, Heidelberg, Germany.

ABSTRACT

Background: Natural killer cells are an important component of the innate immune system. Anti-cancer therapies utilizing monoclonal antibodies also rely on the cytotoxicity of NK cells for their effectiveness. Here, we study the dynamics of NK cell cytotoxicity.

Methodology/principal findings: We observe that IL-2 activated human NK cells can serially hit multiple targets. Using functional assays, we demonstrate that on an average, a single IL-2 activated NK cell can kill four target cells. Data using live video microscopy suggest that an individual NK cell can make serial contacts with multiple targets and majority of contacts lead to lysis of target cells. Serial killing is associated with a loss of Perforin and Granzyme B content. A large majority of NK cells survive serial killing, and IL-2 can replenish their granular stock and restore the diminished cytotoxicity of 'exhausted' NK cells. IL-2 and IL-15 are equally effective in enhancing the killing frequency of resting NK cells. Significantly, Rituximab, a therapeutic monoclonal antibody increases the killing frequency of both resting and IL-2 activated NK cells.

Conclusion/significance: Our data suggest that NK cell-based therapies for overcoming tumors rely on their serial killing ability. Therefore, strategies augmenting the killing ability of NK cells can boost the immune system and enhance the effectiveness of monoclonal antibody-based therapies.

Show MeSH
Related in: MedlinePlus