Antibody-dependent cellular cytotoxicity toward neuroblastoma enhanced by activated invariant natural killer T cells.
Bottom Line: For further improvement in patient outcomes, ways to maximize the cytotoxic effects of anti-GD2 therapies with minimal toxicity are required.Although some of the expanded iNKT cells expressed natural killer (NK) cell markers, including FcγR, iNKT cells were not directly associated with ADCC.In conclusion, iNKT cell-based immunotherapy could be an appropriate candidate for anti-GD2 antibody therapy for neuroblastoma.
Affiliation: Department of Medical Immunology, Graduate School of Medicine, Chiba University, Chiba, Japan.Show MeSH
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Mentions: To clarify whether iNKT cells can recognize anti‐GD2 Ab and are directly associated with ADCC, the FcγR of the expanded iNKT cells were analyzed by flow cytometry. Some of the in vitro‐expanded iNKT cells, mainly CD56+ cells, expressed FcγR. The expression level of FcγR on iNKT cells was lower than that of freshly‐isolated NK cells that expressed a high intensity of FcγR (Fig. 2a). Because ADCC caused by NK and iNKT cells might be influenced by the GD2 expression level of NB cell lines, an in vitro cytotoxicity assay using NK cells against NB cell lines with various GD2 expression levels was performed. NK cells were cultured for 4 h at various E:T ratios with NB cell lines in the presence of anti‐GD2 Abs (14.G2a). ADCC mediated by NK cells toward NMB (high GD2 expression, Fig. 1c) was highest and that toward NLF (low GD2 expression) was lowest. The cytotoxicity toward IMR‐32, which had a heterogeneous expression of GD2, was not as high as that against NMB (Fig. 2b). iNKT cell‐mediated cytotoxicity toward NMB was not increased by the addition of anti‐GD2 Ab (Fig. 2c, right), whereas NK cell‐mediated cytotoxicity was dramatically increased by the addition of anti‐GD2 Ab (Fig. 2c, left). When iNKT cells are activated by APC, it is known that iNKT cells produce a substantial amount of IFNγ. Therefore, iNKT cells were cultured with NB cells in the presence of anti‐GD2 Abs and the IFNγ production was measured. There was no increase of IFNγ production by iNKT cells with NB cells and antibodies (data not shown).
Affiliation: Department of Medical Immunology, Graduate School of Medicine, Chiba University, Chiba, Japan.