Quantitative differences in lipid raft components between murine CD4+ and CD8+ T cells

We found that CD4+CD8- and CD8+CD4- thymocytes at different stages of maturation display distinct GM1 surface expression. This phenomenon did not change with progressive aging, as these findings were consistent over the lifespan of the mouse. In the periphery, CD8+ T cells express significantly higher levels of GM1 than CD4+ T cells. In addition, we observed that GM1 levels increase over aging on CD8+ T cells but not in CD4+ T cells. We also verified that na？ve (CD44lo) and memory (CD44hi) CD8+ T cells as well as na？ve and memory CD4+ T cells express similar levels of GM1 on their surface. Furthermore, we found that CD8+ T cells express higher levels of the GPI-anchored cell surface protein Thy-1 associated with lipid raft domains as compared to CD4+ T cells. Finally, we observed higher levels of total cellular cholesterol in CD8+ T cells than CD4+ T cells.These results demonstrate heterogeneity of lipid raft components between CD4+ and CD8+ T cells in young and aged mice. Such differences in lipid raft composition may contribute to the differential CD4 and CD8 molecule signaling pathways as well as possibly to the effector responses mediated by these T cell subsets following TCR activation.Lipid rafts are characterized as organized plasma membrane domains enriched in sphingolipids and cholesterol, originally identified by their resistance to non-ionic detergent lysis at 4°C [1,2]. These microdomains are enriched in GPI-linked proteins on the extracellular surface, such as Thy-1 and CD59, and acylated signaling proteins on the cytoplasmic surface, including Src kinases, Ras proteins, G proteins, Vav, PKC, and LAT [1-4]. Lipid rafts play an integral role in synapse formation between antigen presenting cells and T cells due to their ability to serve as platforms for the recruitment of TCR and signaling molecules. To identify lipid rafts on the surface of cells, GM1, a monosialoganglioside and glycosphingolipid, is a commonly used marker, which is detected using bacter