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

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

CD16+ but not the CD16− monocytes are able to perform ADCC on therapeutic antibody–coated tumour and virus-infected cell lines.ADCC by CD16+ (left panel) and CD16− (right panel) monocytes on A549 lung adenocarcinoma (A) Raji Burkitt’s lymphoma (B) and SKBR3 breast adenocarcinoma (C) at the indicated effector to target (E:T) cell ratios. Tumour cell lines were either uncoated (open symbols and dotted lines) or pre-coated with the respective therapeutic antibodies αGM2 (KM966), αCD20 (Rituximab) and αHER2 (Trastuzumab) (closed symbols and solid lines). Data shown are representative data of at least 5 independent experiments and plotted as mean ± SD of triplicate wells for each respective experiment. **p ≤ 0.01, ****p ≤ 0.0001 with respect to uncoated target cells at the respective E:T ratios based on Two-way ANOVA (****p ≤ 0.0001). (D) ADCC by CD16+ monocytes on Hepatitis B virus-infected cell line HepG2.2.15 (left) or parental HepG2 (right) cells at E:T ratio of 10:1. Both HepG2 cell lines were either uncoated (white bar) or coated with TCR-like antibodies recognising core or envelope peptides respective (grey bars). Data shown are plotted as mean ± SD; n = 4. ****p ≤ 0.0001 with respect to uncoated cells based on One-way ANOVA (****p ≤ 0.0001). (E) NK cells, CD16+ and CD16− monocytes isolated from the same individual were co-cultured with KM966-coated A549 at an E:T ratio of 10:1. Data plotted is mean ± SD, n = 2. **p ≤ 0.01, ***p ≤ 0.001 and ****p ≤ 0.0001. One-way ANOVA (***p ≤ 0.001).
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f1: CD16+ but not the CD16− monocytes are able to perform ADCC on therapeutic antibody–coated tumour and virus-infected cell lines.ADCC by CD16+ (left panel) and CD16− (right panel) monocytes on A549 lung adenocarcinoma (A) Raji Burkitt’s lymphoma (B) and SKBR3 breast adenocarcinoma (C) at the indicated effector to target (E:T) cell ratios. Tumour cell lines were either uncoated (open symbols and dotted lines) or pre-coated with the respective therapeutic antibodies αGM2 (KM966), αCD20 (Rituximab) and αHER2 (Trastuzumab) (closed symbols and solid lines). Data shown are representative data of at least 5 independent experiments and plotted as mean ± SD of triplicate wells for each respective experiment. **p ≤ 0.01, ****p ≤ 0.0001 with respect to uncoated target cells at the respective E:T ratios based on Two-way ANOVA (****p ≤ 0.0001). (D) ADCC by CD16+ monocytes on Hepatitis B virus-infected cell line HepG2.2.15 (left) or parental HepG2 (right) cells at E:T ratio of 10:1. Both HepG2 cell lines were either uncoated (white bar) or coated with TCR-like antibodies recognising core or envelope peptides respective (grey bars). Data shown are plotted as mean ± SD; n = 4. ****p ≤ 0.0001 with respect to uncoated cells based on One-way ANOVA (****p ≤ 0.0001). (E) NK cells, CD16+ and CD16− monocytes isolated from the same individual were co-cultured with KM966-coated A549 at an E:T ratio of 10:1. Data plotted is mean ± SD, n = 2. **p ≤ 0.01, ***p ≤ 0.001 and ****p ≤ 0.0001. One-way ANOVA (***p ≤ 0.001).

Mentions: When A549, Raji and SKBR3 target cells were co-cultured with either CD16− or CD16+ monocytes for 4 hours in ADCC assay, minimal target cell lysis was detected (Fig. 1A–C; dotted lines). However, when target cells were pre-incubated with 10 μg/ml of their respective antibodies, the CD16+ monocytes lysed between 10% and 40% of the cells, depending on the E:T ratio and cancer cell line used (Fig. 1A–C; left panels solid lines). Percentage specific lysis also increased with increasing E:T ratios. In contrast, co-culture of CD16− monocytes with antibody-coated target cells did not result in increased lysis compared to uncoated target cells (Fig. 1A–C; right panels solid lines), indicating that CD16− monocytes lack ADCC capacity.


CD16 is indispensable for antibody-dependent cellular cytotoxicity by human monocytes
CD16+ but not the CD16− monocytes are able to perform ADCC on therapeutic antibody–coated tumour and virus-infected cell lines.ADCC by CD16+ (left panel) and CD16− (right panel) monocytes on A549 lung adenocarcinoma (A) Raji Burkitt’s lymphoma (B) and SKBR3 breast adenocarcinoma (C) at the indicated effector to target (E:T) cell ratios. Tumour cell lines were either uncoated (open symbols and dotted lines) or pre-coated with the respective therapeutic antibodies αGM2 (KM966), αCD20 (Rituximab) and αHER2 (Trastuzumab) (closed symbols and solid lines). Data shown are representative data of at least 5 independent experiments and plotted as mean ± SD of triplicate wells for each respective experiment. **p ≤ 0.01, ****p ≤ 0.0001 with respect to uncoated target cells at the respective E:T ratios based on Two-way ANOVA (****p ≤ 0.0001). (D) ADCC by CD16+ monocytes on Hepatitis B virus-infected cell line HepG2.2.15 (left) or parental HepG2 (right) cells at E:T ratio of 10:1. Both HepG2 cell lines were either uncoated (white bar) or coated with TCR-like antibodies recognising core or envelope peptides respective (grey bars). Data shown are plotted as mean ± SD; n = 4. ****p ≤ 0.0001 with respect to uncoated cells based on One-way ANOVA (****p ≤ 0.0001). (E) NK cells, CD16+ and CD16− monocytes isolated from the same individual were co-cultured with KM966-coated A549 at an E:T ratio of 10:1. Data plotted is mean ± SD, n = 2. **p ≤ 0.01, ***p ≤ 0.001 and ****p ≤ 0.0001. One-way ANOVA (***p ≤ 0.001).
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f1: CD16+ but not the CD16− monocytes are able to perform ADCC on therapeutic antibody–coated tumour and virus-infected cell lines.ADCC by CD16+ (left panel) and CD16− (right panel) monocytes on A549 lung adenocarcinoma (A) Raji Burkitt’s lymphoma (B) and SKBR3 breast adenocarcinoma (C) at the indicated effector to target (E:T) cell ratios. Tumour cell lines were either uncoated (open symbols and dotted lines) or pre-coated with the respective therapeutic antibodies αGM2 (KM966), αCD20 (Rituximab) and αHER2 (Trastuzumab) (closed symbols and solid lines). Data shown are representative data of at least 5 independent experiments and plotted as mean ± SD of triplicate wells for each respective experiment. **p ≤ 0.01, ****p ≤ 0.0001 with respect to uncoated target cells at the respective E:T ratios based on Two-way ANOVA (****p ≤ 0.0001). (D) ADCC by CD16+ monocytes on Hepatitis B virus-infected cell line HepG2.2.15 (left) or parental HepG2 (right) cells at E:T ratio of 10:1. Both HepG2 cell lines were either uncoated (white bar) or coated with TCR-like antibodies recognising core or envelope peptides respective (grey bars). Data shown are plotted as mean ± SD; n = 4. ****p ≤ 0.0001 with respect to uncoated cells based on One-way ANOVA (****p ≤ 0.0001). (E) NK cells, CD16+ and CD16− monocytes isolated from the same individual were co-cultured with KM966-coated A549 at an E:T ratio of 10:1. Data plotted is mean ± SD, n = 2. **p ≤ 0.01, ***p ≤ 0.001 and ****p ≤ 0.0001. One-way ANOVA (***p ≤ 0.001).
Mentions: When A549, Raji and SKBR3 target cells were co-cultured with either CD16− or CD16+ monocytes for 4 hours in ADCC assay, minimal target cell lysis was detected (Fig. 1A–C; dotted lines). However, when target cells were pre-incubated with 10 μg/ml of their respective antibodies, the CD16+ monocytes lysed between 10% and 40% of the cells, depending on the E:T ratio and cancer cell line used (Fig. 1A–C; left panels solid lines). Percentage specific lysis also increased with increasing E:T ratios. In contrast, co-culture of CD16− monocytes with antibody-coated target cells did not result in increased lysis compared to uncoated target cells (Fig. 1A–C; right panels solid lines), indicating that CD16− monocytes lack ADCC capacity.

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