Figure 4. Cell-intrinsic acid sphingomyelinase (Asm) activity determines CD8⁺ T cell activation in vivo.

(A) B16-F1 melanoma cells were transplanted into Asm/CD4cre mice and wildtype (WT) littermates, and tumor growth was monitored when tumors reached a detectable size (n=12–16). (B) Percentages of CD4⁺ T cells, Foxp3⁺ Tregs, and CD8⁺ T cells within dLN and tumor were determined by flow cytometry, and absolute cell numbers were calculated. Representative dot plots are shown in the upper panel. (C) Expression of IFN-γ, TNF-α, and granzyme B of tumor-infiltrating lymphocytes (TILs) was determined by flow cytometry. Results from four independent experiments are depicted as mean ± SEM. Statistical analysis was performed by two-way ANOVA with Sidak’s multiple comparisons, Mann-Whitney U-test, or Student’s t-test. (*p<0.05, **p<0.01, ***p<0.001).