Introduction:
Ceramide is the central lipid in the sphingolipid metabolism. Due to self-accumulating properties, ceramide is able to form lipid domains in cellular membranes. These ceramide-enriched platforms are involved in signal transduction processes. Cellular ceramide concentrations are regulated by the acid sphingomyelinase (Asm) and acid ceramidase (Ac). Asm catalyzes the cleavage of sphingomyelin to ceramide, while Ac cleaves ceramide to sphingosine. In our study we investigated how cell-intrinsic ceramide concentrations influence CD8+ T cell function in vitro and in vivo.
Objectives:
We aimed to analyze the role of endogenous ceramide concentrations in CD8+ T cell function during tumorigenesis. To modulate ceramide concentrations specifically in T cells we made use of Asm-flox/CD4cre and Ac-flox/CD4cre mice, which lack Asm or Ac expression respectively in T cells.  
Methods:
We transplanted 5x105 B16-F1 melanoma cells subcutaneously into respective mouse strains and monitored tumor growth rates. To analyze the T cell phenotype, we performed flow cytometric analysis of CD8+ T cells isolated from lymphoid organs and tumors of Asm-flox/CD4cre and Ac-flox/CD4cre mice. Furthermore, we stimulated naïve CD8+ T cells from Asm-flox/CD4cre and Ac-flox/CD4cre mice in vitro to determine the impact of ceramide on T cell function.
Results:
We provide evidence that Asm-mediated generation of ceramide promotes CD8+ T cell activation and tumor control, whereas Ac reduces ceramide levels and impairs CD8+ T cell activation and tumor control. Moreover, we demonstrate that ceramide is polarized towards the immunological synapse and is involved in the induction of T cell receptor signaling cascades.
Conclusion:
Our results indicate that endogenous ceramide concentrations have an impact on CD8+ T cell function in vitro and in vivo.