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CD16 is indispensable for antibody-dependent cellular cytotoxicity by human monocytes

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ABSTRACT

Antibody-dependent cellular cytotoxicity (ADCC) is exerted by immune cells expressing surface Fcγ receptors (FcγRs) against cells coated with antibody, such as virus-infected or transformed cells. CD16, the FcγRIIIA, is essential for ADCC by NK cells, and is also expressed by a subset of human blood monocytes. We found that human CD16− expressing monocytes have a broad spectrum of ADCC capacities and can kill cancer cell lines, primary leukemic cells and hepatitis B virus-infected cells in the presence of specific antibodies. Engagement of CD16 on monocytes by antibody bound to target cells activated β2-integrins and induced TNFα secretion. In turn, this induced TNFR expression on the target cells, making them susceptible to TNFα-mediated cell death. Treatment with TLR agonists, DAMPs or cytokines, such as IFNγ, further enhanced ADCC. Monocytes lacking CD16 did not exert ADCC but acquired this property after CD16 expression was induced by either cytokine stimulation or transient transfection. Notably, CD16+ monocytes from patients with leukemia also exerted potent ADCC. Hence, CD16+ monocytes are important effectors of ADCC, suggesting further developments of this property in the context of cellular therapies for cancer and infectious diseases.

No MeSH data available.


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CD16+ monocytes from B-CLL patients exhibit ADCC activity similar to healthy individuals.(A) CD16+ monocytes (left graph) or NK cells (right graph) isolated from the same leukemia patient (striped) or healthy donor (solid) were co-cultured with either uncoated (white bar) or Trast-coated SKBR3 (grey bar) at E:T ratio of 10:1. Data are plotted as mean ± SD, n = 2. ***p ≤ 0.001 based on One-way ANOVA (****p ≤ 0.0001). (B) CD16+ monocytes (left graph) or NK cells (right graph) isolated from the same patient (striped) or healthy donor (solid) were co-cultured with either uncoated (white bar) or Rtx-coated primary B-CLL cells (grey bar) at E:T ratio of 10:1. Data are plotted as mean ± SD, n = 4. **p ≤ 0.01 based on One-way ANOVA (****p ≤ 0.0001).
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f7: CD16+ monocytes from B-CLL patients exhibit ADCC activity similar to healthy individuals.(A) CD16+ monocytes (left graph) or NK cells (right graph) isolated from the same leukemia patient (striped) or healthy donor (solid) were co-cultured with either uncoated (white bar) or Trast-coated SKBR3 (grey bar) at E:T ratio of 10:1. Data are plotted as mean ± SD, n = 2. ***p ≤ 0.001 based on One-way ANOVA (****p ≤ 0.0001). (B) CD16+ monocytes (left graph) or NK cells (right graph) isolated from the same patient (striped) or healthy donor (solid) were co-cultured with either uncoated (white bar) or Rtx-coated primary B-CLL cells (grey bar) at E:T ratio of 10:1. Data are plotted as mean ± SD, n = 4. **p ≤ 0.01 based on One-way ANOVA (****p ≤ 0.0001).

Mentions: NK cells from cancer patients are known to be dysfunctional, i.e. exhibit reduction in ADCC ability151617. We isolated CD16+ monocytes and NK cells from healthy individuals and B-CLL patients and performed ADCC assays using either SKBR3 cell lines or primary B-CLL cells as target cells. The primary B-CLL cells used as target were isolated from patients that were different from those whom NK and CD16+ monocytes were purified. We observed that CD16+ monocytes from patients were able to lyse a significantly higher proportion of trastuzumab-coated SKBR3 cell lines and rituximab-coated primary B-CLL cells as compared to target cells not bound with antibodies (Fig. 7A,B; left panels striped bar respectively). Similar to previous reports, NK cells from B-CLL patients were also able to perform ADCC on both trastuzumab-coated SKBR3 cell lines and rituximab-coated primary B-CLL cells. However, in comparison to healthy individuals, NK cells isolated from B-CLL patients lysed a significantly lower percentage of both trastuzumab-coated SKBR3 cells and rituximab-coated primary B-CLL cells as compared to NK cells from healthy individuals (Fig. 7A,B; right panels respectively). Unlike NK cells, CD16+ monocytes isolated from the same patients could lyse antibody-coated target cells as efficiently as CD16+ monocytes from healthy individuals for both SKBR3 cells and primary B-CLL cells (Fig. 7A,B; left panels respectively).


CD16 is indispensable for antibody-dependent cellular cytotoxicity by human monocytes
CD16+ monocytes from B-CLL patients exhibit ADCC activity similar to healthy individuals.(A) CD16+ monocytes (left graph) or NK cells (right graph) isolated from the same leukemia patient (striped) or healthy donor (solid) were co-cultured with either uncoated (white bar) or Trast-coated SKBR3 (grey bar) at E:T ratio of 10:1. Data are plotted as mean ± SD, n = 2. ***p ≤ 0.001 based on One-way ANOVA (****p ≤ 0.0001). (B) CD16+ monocytes (left graph) or NK cells (right graph) isolated from the same patient (striped) or healthy donor (solid) were co-cultured with either uncoated (white bar) or Rtx-coated primary B-CLL cells (grey bar) at E:T ratio of 10:1. Data are plotted as mean ± SD, n = 4. **p ≤ 0.01 based on One-way ANOVA (****p ≤ 0.0001).
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f7: CD16+ monocytes from B-CLL patients exhibit ADCC activity similar to healthy individuals.(A) CD16+ monocytes (left graph) or NK cells (right graph) isolated from the same leukemia patient (striped) or healthy donor (solid) were co-cultured with either uncoated (white bar) or Trast-coated SKBR3 (grey bar) at E:T ratio of 10:1. Data are plotted as mean ± SD, n = 2. ***p ≤ 0.001 based on One-way ANOVA (****p ≤ 0.0001). (B) CD16+ monocytes (left graph) or NK cells (right graph) isolated from the same patient (striped) or healthy donor (solid) were co-cultured with either uncoated (white bar) or Rtx-coated primary B-CLL cells (grey bar) at E:T ratio of 10:1. Data are plotted as mean ± SD, n = 4. **p ≤ 0.01 based on One-way ANOVA (****p ≤ 0.0001).
Mentions: NK cells from cancer patients are known to be dysfunctional, i.e. exhibit reduction in ADCC ability151617. We isolated CD16+ monocytes and NK cells from healthy individuals and B-CLL patients and performed ADCC assays using either SKBR3 cell lines or primary B-CLL cells as target cells. The primary B-CLL cells used as target were isolated from patients that were different from those whom NK and CD16+ monocytes were purified. We observed that CD16+ monocytes from patients were able to lyse a significantly higher proportion of trastuzumab-coated SKBR3 cell lines and rituximab-coated primary B-CLL cells as compared to target cells not bound with antibodies (Fig. 7A,B; left panels striped bar respectively). Similar to previous reports, NK cells from B-CLL patients were also able to perform ADCC on both trastuzumab-coated SKBR3 cell lines and rituximab-coated primary B-CLL cells. However, in comparison to healthy individuals, NK cells isolated from B-CLL patients lysed a significantly lower percentage of both trastuzumab-coated SKBR3 cells and rituximab-coated primary B-CLL cells as compared to NK cells from healthy individuals (Fig. 7A,B; right panels respectively). Unlike NK cells, CD16+ monocytes isolated from the same patients could lyse antibody-coated target cells as efficiently as CD16+ monocytes from healthy individuals for both SKBR3 cells and primary B-CLL cells (Fig. 7A,B; left panels respectively).

View Article: PubMed Central - PubMed

ABSTRACT

Antibody-dependent cellular cytotoxicity (ADCC) is exerted by immune cells expressing surface Fcγ receptors (FcγRs) against cells coated with antibody, such as virus-infected or transformed cells. CD16, the FcγRIIIA, is essential for ADCC by NK cells, and is also expressed by a subset of human blood monocytes. We found that human CD16− expressing monocytes have a broad spectrum of ADCC capacities and can kill cancer cell lines, primary leukemic cells and hepatitis B virus-infected cells in the presence of specific antibodies. Engagement of CD16 on monocytes by antibody bound to target cells activated β2-integrins and induced TNFα secretion. In turn, this induced TNFR expression on the target cells, making them susceptible to TNFα-mediated cell death. Treatment with TLR agonists, DAMPs or cytokines, such as IFNγ, further enhanced ADCC. Monocytes lacking CD16 did not exert ADCC but acquired this property after CD16 expression was induced by either cytokine stimulation or transient transfection. Notably, CD16+ monocytes from patients with leukemia also exerted potent ADCC. Hence, CD16+ monocytes are important effectors of ADCC, suggesting further developments of this property in the context of cellular therapies for cancer and infectious diseases.

No MeSH data available.


Related in: MedlinePlus