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Targeting IL-10 abrogates ATL LIC
critical role for macrophages and NK cells of the primary donor mice in AS/IFNα-induced abrogation of ATL LIC activity.
These results prompted us to deplete macrophages or NK cells in the recipient mice using clodronate or anti- NK1.1 antibody, respectively. For macrophage depletion in the recipient mice, we used clodronate treatment.27 Secondary recipient SCID mice, injected with 106 unsort- ed spleen cells from either untreated or AS/IFNα-treated primary mice, were treated with empty liposomes or clo-
dronate (see experimental design in Figure 2B). Macrophage depletion was confirmed by flow cytometry based on the reduction of CD25–CD11b+F4/80+ cells (Online Supplementary Figure S2B). Clodronate treatment abrogated the effects of AS/IFNα and restored ATL LIC activity (Figure 2B, Online Supplementary Figure S2B), con- firming the critical role of macrophages of secondary recipients in the AS/IFNα-induced cure.
For NK-cell depletion in the recipient mice, secondary recipient SCID mice, injected with 106 unsorted spleen
ABC
D
Figure 4. Loss of leukemia-initiating cell activity requires innate immunity. (A) Primary mice injected with cells, derived from the tumoral spleen of tax transgenic mice that developed adult T-cell leukemia/lymphoma (ATL), were treated with arsenic trioxide (AS) and interferon alpha (IFNα) for 3 days then sacrificed. One million unsorted spleen-derived cells were injected into 50 secondary SCID mice that were left untreated and sacrificed on a weekly basis (5 per week). (B, C) One million unsorted spleen cells derived from weekly sacrificed untreated secondary SCID mice were injected into tertiary SCID (green histograms) (B) or NOG SCID (dark blue histograms) (n=10/condition) (C) mice that were left untreated. (D) Enzyme-linked immunosorbent assay on supernatant of homogenized spleen-derived CD25+ and CD25– sorted cells from weekly sacrificed untreated secondary mice injected with 106 unsorted spleen cells from AS/IFNα-treated primary mice. Control indicates secondary mice injected with 106 unsorted spleen cells from untreated primary mice. The t-test was performed to validate significance. *P≤0.05, **P≤0.01, and ***P≤0.001. P-values ≤0.05 were considered statistically significant.
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