Extended Data Fig. 8: Immunophenotyping of B16-GMCSF tumors.

a–c, Mass cytometry analysis of tumor-infiltrating leukocytes isolated at day 14 after B16-GMCSF tumor cell inoculation as described in Fig. 5 (n = 3 mice per group). t-SNE plot of tumor-infiltrating leukocytes overlaid with the expression of indicated markers (a). Density t-SNE plots of an equal number of CD45⁺ tumor-infiltrating leukocytes in Siglec-15 KO and WT mice (b). The normalized expression value (mean mass intensity) of checkpoint receptors on tumor-infiltrating CD8⁺ T cells (c). d,e, On day 14 after B16-GMCSF tumor cell inoculation, spleens and lymph nodes (LN) from WT and KO mice were dissected (d). The percentage of CD4⁺ and CD8⁺ T cells in the draining and non-draining lymph nodes (LN) was analyzed by flow cytometry (e). Data are mean ± s.e.m. (n = 4 mice per group). P values by two-tailed unpaired t-test. f, B16-GMCSF tumor cells were injected subcutaneously into Siglec-15 WT and KO at 1.5 × 10⁶ per mouse. Mice were treated with 200 μg anti-CD8 antibody every 3–4 days since 3 days before tumor inoculation. Tumor growth was measured regularly and is shown as the mean tumor diameter ± s.e.m. (n = 5 mice per group). P values by two-way ANOVA (n.s., not significant; P = 0.9372).